move down py/impl/XYZ to py/_XYZ

--HG--
branch : trunk

py/_code/__init__.py

@@ -0,0 +1 @@
+""" python inspection/code generation API """

py/_code/_assertionnew.py

@@ -0,0 +1,337 @@
+"""
+Like _assertion.py but using builtin AST.  It should replace _assertion.py
+eventually.
+"""
+
+import sys
+import ast
+
+import py
+from py._code.assertion import _format_explanation, BuiltinAssertionError
+
+
+if sys.platform.startswith("java") and sys.version_info < (2, 5, 2):
+    # See http://bugs.jython.org/issue1497
+    _exprs = ("BoolOp", "BinOp", "UnaryOp", "Lambda", "IfExp", "Dict",
+              "ListComp", "GeneratorExp", "Yield", "Compare", "Call",
+              "Repr", "Num", "Str", "Attribute", "Subscript", "Name",
+              "List", "Tuple")
+    _stmts = ("FunctionDef", "ClassDef", "Return", "Delete", "Assign",
+              "AugAssign", "Print", "For", "While", "If", "With", "Raise",
+              "TryExcept", "TryFinally", "Assert", "Import", "ImportFrom",
+              "Exec", "Global", "Expr", "Pass", "Break", "Continue")
+    _expr_nodes = set(getattr(ast, name) for name in _exprs)
+    _stmt_nodes = set(getattr(ast, name) for name in _stmts)
+    def _is_ast_expr(node):
+        return node.__class__ in _expr_nodes
+    def _is_ast_stmt(node):
+        return node.__class__ in _stmt_nodes
+else:
+    def _is_ast_expr(node):
+        return isinstance(node, ast.expr)
+    def _is_ast_stmt(node):
+        return isinstance(node, ast.stmt)
+
+
+class Failure(Exception):
+    """Error found while interpreting AST."""
+
+    def __init__(self, explanation=""):
+        self.cause = sys.exc_info()
+        self.explanation = explanation
+
+
+def interpret(source, frame, should_fail=False):
+    mod = ast.parse(source)
+    visitor = DebugInterpreter(frame)
+    try:
+        visitor.visit(mod)
+    except Failure:
+        failure = sys.exc_info()[1]
+        return getfailure(failure)
+    if should_fail:
+        return ("(assertion failed, but when it was re-run for "
+                "printing intermediate values, it did not fail.  Suggestions: "
+                "compute assert expression before the assert or use --no-assert)")
+
+def run(offending_line, frame=None):
+    if frame is None:
+        frame = py.code.Frame(sys._getframe(1))
+    return interpret(offending_line, frame)
+
+def getfailure(failure):
+    explanation = _format_explanation(failure.explanation)
+    value = failure.cause[1]
+    if str(value):
+        lines = explanation.splitlines()
+        if not lines:
+            lines.append("")
+        lines[0] += " << %s" % (value,)
+        explanation = "\n".join(lines)
+    text = "%s: %s" % (failure.cause[0].__name__, explanation)
+    if text.startswith("AssertionError: assert "):
+        text = text[16:]
+    return text
+
+
+operator_map = {
+    ast.BitOr : "|",
+    ast.BitXor : "^",
+    ast.BitAnd : "&",
+    ast.LShift : "<<",
+    ast.RShift : ">>",
+    ast.Add : "+",
+    ast.Sub : "-",
+    ast.Mult : "*",
+    ast.Div : "/",
+    ast.FloorDiv : "//",
+    ast.Mod : "%",
+    ast.Eq : "==",
+    ast.NotEq : "!=",
+    ast.Lt : "<",
+    ast.LtE : "<=",
+    ast.Gt : ">",
+    ast.GtE : ">=",
+    ast.Is : "is",
+    ast.IsNot : "is not",
+    ast.In : "in",
+    ast.NotIn : "not in"
+}
+
+unary_map = {
+    ast.Not : "not %s",
+    ast.Invert : "~%s",
+    ast.USub : "-%s",
+    ast.UAdd : "+%s"
+}
+
+
+class DebugInterpreter(ast.NodeVisitor):
+    """Interpret AST nodes to gleam useful debugging information."""
+
+    def __init__(self, frame):
+        self.frame = frame
+
+    def generic_visit(self, node):
+        # Fallback when we don't have a special implementation.
+        if _is_ast_expr(node):
+            mod = ast.Expression(node)
+            co = self._compile(mod)
+            try:
+                result = self.frame.eval(co)
+            except Exception:
+                raise Failure()
+            explanation = self.frame.repr(result)
+            return explanation, result
+        elif _is_ast_stmt(node):
+            mod = ast.Module([node])
+            co = self._compile(mod, "exec")
+            try:
+                self.frame.exec_(co)
+            except Exception:
+                raise Failure()
+            return None, None
+        else:
+            raise AssertionError("can't handle %s" %(node,))
+
+    def _compile(self, source, mode="eval"):
+        return compile(source, "<assertion interpretation>", mode)
+
+    def visit_Expr(self, expr):
+        return self.visit(expr.value)
+
+    def visit_Module(self, mod):
+        for stmt in mod.body:
+            self.visit(stmt)
+
+    def visit_Name(self, name):
+        explanation, result = self.generic_visit(name)
+        # See if the name is local.
+        source = "%r in locals() is not globals()" % (name.id,)
+        co = self._compile(source)
+        try:
+            local = self.frame.eval(co)
+        except Exception:
+            # have to assume it isn't
+            local = False
+        if not local:
+            return name.id, result
+        return explanation, result
+
+    def visit_Compare(self, comp):
+        left = comp.left
+        left_explanation, left_result = self.visit(left)
+        got_result = False
+        for op, next_op in zip(comp.ops, comp.comparators):
+            if got_result and not result:
+                break
+            next_explanation, next_result = self.visit(next_op)
+            op_symbol = operator_map[op.__class__]
+            explanation = "%s %s %s" % (left_explanation, op_symbol,
+                                        next_explanation)
+            source = "__exprinfo_left %s __exprinfo_right" % (op_symbol,)
+            co = self._compile(source)
+            try:
+                result = self.frame.eval(co, __exprinfo_left=left_result,
+                                         __exprinfo_right=next_result)
+            except Exception:
+                raise Failure(explanation)
+            else:
+                got_result = True
+            left_explanation, left_result = next_explanation, next_result
+        return explanation, result
+
+    def visit_BoolOp(self, boolop):
+        is_or = isinstance(boolop.op, ast.Or)
+        explanations = []
+        for operand in boolop.values:
+            explanation, result = self.visit(operand)
+            explanations.append(explanation)
+            if result == is_or:
+                break
+        name = is_or and " or " or " and "
+        explanation = "(" + name.join(explanations) + ")"
+        return explanation, result
+
+    def visit_UnaryOp(self, unary):
+        pattern = unary_map[unary.op.__class__]
+        operand_explanation, operand_result = self.visit(unary.operand)
+        explanation = pattern % (operand_explanation,)
+        co = self._compile(pattern % ("__exprinfo_expr",))
+        try:
+            result = self.frame.eval(co, __exprinfo_expr=operand_result)
+        except Exception:
+            raise Failure(explanation)
+        return explanation, result
+
+    def visit_BinOp(self, binop):
+        left_explanation, left_result = self.visit(binop.left)
+        right_explanation, right_result = self.visit(binop.right)
+        symbol = operator_map[binop.op.__class__]
+        explanation = "(%s %s %s)" % (left_explanation, symbol,
+                                      right_explanation)
+        source = "__exprinfo_left %s __exprinfo_right" % (symbol,)
+        co = self._compile(source)
+        try:
+            result = self.frame.eval(co, __exprinfo_left=left_result,
+                                     __exprinfo_right=right_result)
+        except Exception:
+            raise Failure(explanation)
+        return explanation, result
+
+    def visit_Call(self, call):
+        func_explanation, func = self.visit(call.func)
+        arg_explanations = []
+        ns = {"__exprinfo_func" : func}
+        arguments = []
+        for arg in call.args:
+            arg_explanation, arg_result = self.visit(arg)
+            arg_name = "__exprinfo_%s" % (len(ns),)
+            ns[arg_name] = arg_result
+            arguments.append(arg_name)
+            arg_explanations.append(arg_explanation)
+        for keyword in call.keywords:
+            arg_explanation, arg_result = self.visit(keyword.value)
+            arg_name = "__exprinfo_%s" % (len(ns),)
+            ns[arg_name] = arg_result
+            keyword_source = "%s=%%s" % (keyword.arg)
+            arguments.append(keyword_source % (arg_name,))
+            arg_explanations.append(keyword_source % (arg_explanation,))
+        if call.starargs:
+            arg_explanation, arg_result = self.visit(call.starargs)
+            arg_name = "__exprinfo_star"
+            ns[arg_name] = arg_result
+            arguments.append("*%s" % (arg_name,))
+            arg_explanations.append("*%s" % (arg_explanation,))
+        if call.kwargs:
+            arg_explanation, arg_result = self.visit(call.kwargs)
+            arg_name = "__exprinfo_kwds"
+            ns[arg_name] = arg_result
+            arguments.append("**%s" % (arg_name,))
+            arg_explanations.append("**%s" % (arg_explanation,))
+        args_explained = ", ".join(arg_explanations)
+        explanation = "%s(%s)" % (func_explanation, args_explained)
+        args = ", ".join(arguments)
+        source = "__exprinfo_func(%s)" % (args,)
+        co = self._compile(source)
+        try:
+            result = self.frame.eval(co, **ns)
+        except Exception:
+            raise Failure(explanation)
+        # Only show result explanation if it's not a builtin call or returns a
+        # bool.
+        if not isinstance(call.func, ast.Name) or \
+                not self._is_builtin_name(call.func):
+            source = "isinstance(__exprinfo_value, bool)"
+            co = self._compile(source)
+            try:
+                is_bool = self.frame.eval(co, __exprinfo_value=result)
+            except Exception:
+                is_bool = False
+            if not is_bool:
+                pattern = "%s\n{%s = %s\n}"
+                rep = self.frame.repr(result)
+                explanation = pattern % (rep, rep, explanation)
+        return explanation, result
+
+    def _is_builtin_name(self, name):
+        pattern = "%r not in globals() and %r not in locals()"
+        source = pattern % (name.id, name.id)
+        co = self._compile(source)
+        try:
+            return self.frame.eval(co)
+        except Exception:
+            return False
+
+    def visit_Attribute(self, attr):
+        if not isinstance(attr.ctx, ast.Load):
+            return self.generic_visit(attr)
+        source_explanation, source_result = self.visit(attr.value)
+        explanation = "%s.%s" % (source_explanation, attr.attr)
+        source = "__exprinfo_expr.%s" % (attr.attr,)
+        co = self._compile(source)
+        try:
+            result = self.frame.eval(co, __exprinfo_expr=source_result)
+        except Exception:
+            raise Failure(explanation)
+        # Check if the attr is from an instance.
+        source = "%r in getattr(__exprinfo_expr, '__dict__', {})"
+        source = source % (attr.attr,)
+        co = self._compile(source)
+        try:
+            from_instance = self.frame.eval(co, __exprinfo_expr=source_result)
+        except Exception:
+            from_instance = True
+        if from_instance:
+            rep = self.frame.repr(result)
+            pattern = "%s\n{%s = %s\n}"
+            explanation = pattern % (rep, rep, explanation)
+        return explanation, result
+
+    def visit_Assert(self, assrt):
+        test_explanation, test_result = self.visit(assrt.test)
+        if test_explanation.startswith("False\n{False =") and \
+                test_explanation.endswith("\n"):
+            test_explanation = test_explanation[15:-2]
+        explanation = "assert %s" % (test_explanation,)
+        if not test_result:
+            try:
+                raise BuiltinAssertionError
+            except Exception:
+                raise Failure(explanation)
+        return explanation, test_result
+
+    def visit_Assign(self, assign):
+        value_explanation, value_result = self.visit(assign.value)
+        explanation = "... = %s" % (value_explanation,)
+        name = ast.Name("__exprinfo_expr", ast.Load(), assign.value.lineno,
+                        assign.value.col_offset)
+        new_assign = ast.Assign(assign.targets, name, assign.lineno,
+                                assign.col_offset)
+        mod = ast.Module([new_assign])
+        co = self._compile(mod, "exec")
+        try:
+            self.frame.exec_(co, __exprinfo_expr=value_result)
+        except Exception:
+            raise Failure(explanation)
+        return explanation, value_result

py/_code/_assertionold.py

@@ -0,0 +1,558 @@
+import py
+import sys, inspect
+from compiler import parse, ast, pycodegen
+from py._code.assertion import BuiltinAssertionError, _format_explanation
+
+passthroughex = (KeyboardInterrupt, SystemExit, MemoryError)
+
+class Failure:
+    def __init__(self, node):
+        self.exc, self.value, self.tb = sys.exc_info()
+        self.node = node
+
+class View(object):
+    """View base class.
+
+    If C is a subclass of View, then C(x) creates a proxy object around
+    the object x.  The actual class of the proxy is not C in general,
+    but a *subclass* of C determined by the rules below.  To avoid confusion
+    we call view class the class of the proxy (a subclass of C, so of View)
+    and object class the class of x.
+
+    Attributes and methods not found in the proxy are automatically read on x.
+    Other operations like setting attributes are performed on the proxy, as
+    determined by its view class.  The object x is available from the proxy
+    as its __obj__ attribute.
+
+    The view class selection is determined by the __view__ tuples and the
+    optional __viewkey__ method.  By default, the selected view class is the
+    most specific subclass of C whose __view__ mentions the class of x.
+    If no such subclass is found, the search proceeds with the parent
+    object classes.  For example, C(True) will first look for a subclass
+    of C with __view__ = (..., bool, ...) and only if it doesn't find any
+    look for one with __view__ = (..., int, ...), and then ..., object,...
+    If everything fails the class C itself is considered to be the default.
+
+    Alternatively, the view class selection can be driven by another aspect
+    of the object x, instead of the class of x, by overriding __viewkey__.
+    See last example at the end of this module.
+    """
+
+    _viewcache = {}
+    __view__ = ()
+
+    def __new__(rootclass, obj, *args, **kwds):
+        self = object.__new__(rootclass)
+        self.__obj__ = obj
+        self.__rootclass__ = rootclass
+        key = self.__viewkey__()
+        try:
+            self.__class__ = self._viewcache[key]
+        except KeyError:
+            self.__class__ = self._selectsubclass(key)
+        return self
+
+    def __getattr__(self, attr):
+        # attributes not found in the normal hierarchy rooted on View
+        # are looked up in the object's real class
+        return getattr(self.__obj__, attr)
+
+    def __viewkey__(self):
+        return self.__obj__.__class__
+
+    def __matchkey__(self, key, subclasses):
+        if inspect.isclass(key):
+            keys = inspect.getmro(key)
+        else:
+            keys = [key]
+        for key in keys:
+            result = [C for C in subclasses if key in C.__view__]
+            if result:
+                return result
+        return []
+
+    def _selectsubclass(self, key):
+        subclasses = list(enumsubclasses(self.__rootclass__))
+        for C in subclasses:
+            if not isinstance(C.__view__, tuple):
+                C.__view__ = (C.__view__,)
+        choices = self.__matchkey__(key, subclasses)
+        if not choices:
+            return self.__rootclass__
+        elif len(choices) == 1:
+            return choices[0]
+        else:
+            # combine the multiple choices
+            return type('?', tuple(choices), {})
+
+    def __repr__(self):
+        return '%s(%r)' % (self.__rootclass__.__name__, self.__obj__)
+
+
+def enumsubclasses(cls):
+    for subcls in cls.__subclasses__():
+        for subsubclass in enumsubclasses(subcls):
+            yield subsubclass
+    yield cls
+
+
+class Interpretable(View):
+    """A parse tree node with a few extra methods."""
+    explanation = None
+
+    def is_builtin(self, frame):
+        return False
+
+    def eval(self, frame):
+        # fall-back for unknown expression nodes
+        try:
+            expr = ast.Expression(self.__obj__)
+            expr.filename = '<eval>'
+            self.__obj__.filename = '<eval>'
+            co = pycodegen.ExpressionCodeGenerator(expr).getCode()
+            result = frame.eval(co)
+        except passthroughex:
+            raise
+        except:
+            raise Failure(self)
+        self.result = result
+        self.explanation = self.explanation or frame.repr(self.result)
+
+    def run(self, frame):
+        # fall-back for unknown statement nodes
+        try:
+            expr = ast.Module(None, ast.Stmt([self.__obj__]))
+            expr.filename = '<run>'
+            co = pycodegen.ModuleCodeGenerator(expr).getCode()
+            frame.exec_(co)
+        except passthroughex:
+            raise
+        except:
+            raise Failure(self)
+
+    def nice_explanation(self):
+        return _format_explanation(self.explanation)
+
+
+class Name(Interpretable):
+    __view__ = ast.Name
+
+    def is_local(self, frame):
+        co = compile('%r in locals() is not globals()' % self.name, '?', 'eval')
+        try:
+            return frame.is_true(frame.eval(co))
+        except passthroughex:
+            raise
+        except:
+            return False
+
+    def is_global(self, frame):
+        co = compile('%r in globals()' % self.name, '?', 'eval')
+        try:
+            return frame.is_true(frame.eval(co))
+        except passthroughex:
+            raise
+        except:
+            return False
+
+    def is_builtin(self, frame):
+        co = compile('%r not in locals() and %r not in globals()' % (
+            self.name, self.name), '?', 'eval')
+        try:
+            return frame.is_true(frame.eval(co))
+        except passthroughex:
+            raise
+        except:
+            return False
+
+    def eval(self, frame):
+        super(Name, self).eval(frame)
+        if not self.is_local(frame):
+            self.explanation = self.name
+
+class Compare(Interpretable):
+    __view__ = ast.Compare
+
+    def eval(self, frame):
+        expr = Interpretable(self.expr)
+        expr.eval(frame)
+        for operation, expr2 in self.ops:
+            if hasattr(self, 'result'):
+                # shortcutting in chained expressions
+                if not frame.is_true(self.result):
+                    break
+            expr2 = Interpretable(expr2)
+            expr2.eval(frame)
+            self.explanation = "%s %s %s" % (
+                expr.explanation, operation, expr2.explanation)
+            co = compile("__exprinfo_left %s __exprinfo_right" % operation,
+                         '?', 'eval')
+            try:
+                self.result = frame.eval(co, __exprinfo_left=expr.result,
+                                             __exprinfo_right=expr2.result)
+            except passthroughex:
+                raise
+            except:
+                raise Failure(self)
+            expr = expr2
+
+class And(Interpretable):
+    __view__ = ast.And
+
+    def eval(self, frame):
+        explanations = []
+        for expr in self.nodes:
+            expr = Interpretable(expr)
+            expr.eval(frame)
+            explanations.append(expr.explanation)
+            self.result = expr.result
+            if not frame.is_true(expr.result):
+                break
+        self.explanation = '(' + ' and '.join(explanations) + ')'
+
+class Or(Interpretable):
+    __view__ = ast.Or
+
+    def eval(self, frame):
+        explanations = []
+        for expr in self.nodes:
+            expr = Interpretable(expr)
+            expr.eval(frame)
+            explanations.append(expr.explanation)
+            self.result = expr.result
+            if frame.is_true(expr.result):
+                break
+        self.explanation = '(' + ' or '.join(explanations) + ')'
+
+
+# == Unary operations ==
+keepalive = []
+for astclass, astpattern in {
+    ast.Not    : 'not __exprinfo_expr',
+    ast.Invert : '(~__exprinfo_expr)',
+    }.items():
+
+    class UnaryArith(Interpretable):
+        __view__ = astclass
+
+        def eval(self, frame, astpattern=astpattern,
+                              co=compile(astpattern, '?', 'eval')):
+            expr = Interpretable(self.expr)
+            expr.eval(frame)
+            self.explanation = astpattern.replace('__exprinfo_expr',
+                                                  expr.explanation)
+            try:
+                self.result = frame.eval(co, __exprinfo_expr=expr.result)
+            except passthroughex:
+                raise
+            except:
+                raise Failure(self)
+
+    keepalive.append(UnaryArith)
+
+# == Binary operations ==
+for astclass, astpattern in {
+    ast.Add    : '(__exprinfo_left + __exprinfo_right)',
+    ast.Sub    : '(__exprinfo_left - __exprinfo_right)',
+    ast.Mul    : '(__exprinfo_left * __exprinfo_right)',
+    ast.Div    : '(__exprinfo_left / __exprinfo_right)',
+    ast.Mod    : '(__exprinfo_left % __exprinfo_right)',
+    ast.Power  : '(__exprinfo_left ** __exprinfo_right)',
+    }.items():
+
+    class BinaryArith(Interpretable):
+        __view__ = astclass
+
+        def eval(self, frame, astpattern=astpattern,
+                              co=compile(astpattern, '?', 'eval')):
+            left = Interpretable(self.left)
+            left.eval(frame)
+            right = Interpretable(self.right)
+            right.eval(frame)
+            self.explanation = (astpattern
+                                .replace('__exprinfo_left',  left .explanation)
+                                .replace('__exprinfo_right', right.explanation))
+            try:
+                self.result = frame.eval(co, __exprinfo_left=left.result,
+                                             __exprinfo_right=right.result)
+            except passthroughex:
+                raise
+            except:
+                raise Failure(self)
+
+    keepalive.append(BinaryArith)
+
+
+class CallFunc(Interpretable):
+    __view__ = ast.CallFunc
+
+    def is_bool(self, frame):
+        co = compile('isinstance(__exprinfo_value, bool)', '?', 'eval')
+        try:
+            return frame.is_true(frame.eval(co, __exprinfo_value=self.result))
+        except passthroughex:
+            raise
+        except:
+            return False
+
+    def eval(self, frame):
+        node = Interpretable(self.node)
+        node.eval(frame)
+        explanations = []
+        vars = {'__exprinfo_fn': node.result}
+        source = '__exprinfo_fn('
+        for a in self.args:
+            if isinstance(a, ast.Keyword):
+                keyword = a.name
+                a = a.expr
+            else:
+                keyword = None
+            a = Interpretable(a)
+            a.eval(frame)
+            argname = '__exprinfo_%d' % len(vars)
+            vars[argname] = a.result
+            if keyword is None:
+                source += argname + ','
+                explanations.append(a.explanation)
+            else:
+                source += '%s=%s,' % (keyword, argname)
+                explanations.append('%s=%s' % (keyword, a.explanation))
+        if self.star_args:
+            star_args = Interpretable(self.star_args)
+            star_args.eval(frame)
+            argname = '__exprinfo_star'
+            vars[argname] = star_args.result
+            source += '*' + argname + ','
+            explanations.append('*' + star_args.explanation)
+        if self.dstar_args:
+            dstar_args = Interpretable(self.dstar_args)
+            dstar_args.eval(frame)
+            argname = '__exprinfo_kwds'
+            vars[argname] = dstar_args.result
+            source += '**' + argname + ','
+            explanations.append('**' + dstar_args.explanation)
+        self.explanation = "%s(%s)" % (
+            node.explanation, ', '.join(explanations))
+        if source.endswith(','):
+            source = source[:-1]
+        source += ')'
+        co = compile(source, '?', 'eval')
+        try:
+            self.result = frame.eval(co, **vars)
+        except passthroughex:
+            raise
+        except:
+            raise Failure(self)
+        if not node.is_builtin(frame) or not self.is_bool(frame):
+            r = frame.repr(self.result)
+            self.explanation = '%s\n{%s = %s\n}' % (r, r, self.explanation)
+
+class Getattr(Interpretable):
+    __view__ = ast.Getattr
+
+    def eval(self, frame):
+        expr = Interpretable(self.expr)
+        expr.eval(frame)
+        co = compile('__exprinfo_expr.%s' % self.attrname, '?', 'eval')
+        try:
+            self.result = frame.eval(co, __exprinfo_expr=expr.result)
+        except passthroughex:
+            raise
+        except:
+            raise Failure(self)
+        self.explanation = '%s.%s' % (expr.explanation, self.attrname)
+        # if the attribute comes from the instance, its value is interesting
+        co = compile('hasattr(__exprinfo_expr, "__dict__") and '
+                     '%r in __exprinfo_expr.__dict__' % self.attrname,
+                     '?', 'eval')
+        try:
+            from_instance = frame.is_true(
+                frame.eval(co, __exprinfo_expr=expr.result))
+        except passthroughex:
+            raise
+        except:
+            from_instance = True
+        if from_instance:
+            r = frame.repr(self.result)
+            self.explanation = '%s\n{%s = %s\n}' % (r, r, self.explanation)
+
+# == Re-interpretation of full statements ==
+
+class Assert(Interpretable):
+    __view__ = ast.Assert
+
+    def run(self, frame):
+        test = Interpretable(self.test)
+        test.eval(frame)
+        # simplify 'assert False where False = ...'
+        if (test.explanation.startswith('False\n{False = ') and
+            test.explanation.endswith('\n}')):
+            test.explanation = test.explanation[15:-2]
+        # print the result as  'assert <explanation>'
+        self.result = test.result
+        self.explanation = 'assert ' + test.explanation
+        if not frame.is_true(test.result):
+            try:
+                raise BuiltinAssertionError
+            except passthroughex:
+                raise
+            except:
+                raise Failure(self)
+
+class Assign(Interpretable):
+    __view__ = ast.Assign
+
+    def run(self, frame):
+        expr = Interpretable(self.expr)
+        expr.eval(frame)
+        self.result = expr.result
+        self.explanation = '... = ' + expr.explanation
+        # fall-back-run the rest of the assignment
+        ass = ast.Assign(self.nodes, ast.Name('__exprinfo_expr'))
+        mod = ast.Module(None, ast.Stmt([ass]))
+        mod.filename = '<run>'
+        co = pycodegen.ModuleCodeGenerator(mod).getCode()
+        try:
+            frame.exec_(co, __exprinfo_expr=expr.result)
+        except passthroughex:
+            raise
+        except:
+            raise Failure(self)
+
+class Discard(Interpretable):
+    __view__ = ast.Discard
+
+    def run(self, frame):
+        expr = Interpretable(self.expr)
+        expr.eval(frame)
+        self.result = expr.result
+        self.explanation = expr.explanation
+
+class Stmt(Interpretable):
+    __view__ = ast.Stmt
+
+    def run(self, frame):
+        for stmt in self.nodes:
+            stmt = Interpretable(stmt)
+            stmt.run(frame)
+
+
+def report_failure(e):
+    explanation = e.node.nice_explanation()
+    if explanation:
+        explanation = ", in: " + explanation
+    else:
+        explanation = ""
+    sys.stdout.write("%s: %s%s\n" % (e.exc.__name__, e.value, explanation))
+
+def check(s, frame=None):
+    if frame is None:
+        import sys
+        frame = sys._getframe(1)
+        frame = py.code.Frame(frame)
+    expr = parse(s, 'eval')
+    assert isinstance(expr, ast.Expression)
+    node = Interpretable(expr.node)
+    try:
+        node.eval(frame)
+    except passthroughex:
+        raise
+    except Failure:
+        e = sys.exc_info()[1]
+        report_failure(e)
+    else:
+        if not frame.is_true(node.result):
+            sys.stderr.write("assertion failed: %s\n" % node.nice_explanation())
+
+
+###########################################################
+# API / Entry points
+# #########################################################
+
+def interpret(source, frame, should_fail=False):
+    module = Interpretable(parse(source, 'exec').node)
+    #print "got module", module
+    if isinstance(frame, py.std.types.FrameType):
+        frame = py.code.Frame(frame)
+    try:
+        module.run(frame)
+    except Failure:
+        e = sys.exc_info()[1]
+        return getfailure(e)
+    except passthroughex:
+        raise
+    except:
+        import traceback
+        traceback.print_exc()
+    if should_fail:
+        return ("(assertion failed, but when it was re-run for "
+                "printing intermediate values, it did not fail.  Suggestions: "
+                "compute assert expression before the assert or use --nomagic)")
+    else:
+        return None
+
+def getmsg(excinfo):
+    if isinstance(excinfo, tuple):
+        excinfo = py.code.ExceptionInfo(excinfo)
+    #frame, line = gettbline(tb)
+    #frame = py.code.Frame(frame)
+    #return interpret(line, frame)
+
+    tb = excinfo.traceback[-1] 
+    source = str(tb.statement).strip()
+    x = interpret(source, tb.frame, should_fail=True)
+    if not isinstance(x, str):
+        raise TypeError("interpret returned non-string %r" % (x,))
+    return x
+
+def getfailure(e):
+    explanation = e.node.nice_explanation()
+    if str(e.value):
+        lines = explanation.split('\n')
+        lines[0] += "  << %s" % (e.value,)
+        explanation = '\n'.join(lines)
+    text = "%s: %s" % (e.exc.__name__, explanation)
+    if text.startswith('AssertionError: assert '):
+        text = text[16:]
+    return text
+
+def run(s, frame=None):
+    if frame is None:
+        import sys
+        frame = sys._getframe(1)
+        frame = py.code.Frame(frame)
+    module = Interpretable(parse(s, 'exec').node)
+    try:
+        module.run(frame)
+    except Failure:
+        e = sys.exc_info()[1]
+        report_failure(e)
+
+
+if __name__ == '__main__':
+    # example:
+    def f():
+        return 5
+    def g():
+        return 3
+    def h(x):
+        return 'never'
+    check("f() * g() == 5")
+    check("not f()")
+    check("not (f() and g() or 0)")
+    check("f() == g()")
+    i = 4
+    check("i == f()")
+    check("len(f()) == 0")
+    check("isinstance(2+3+4, float)")
+
+    run("x = i")
+    check("x == 5")
+
+    run("assert not f(), 'oops'")
+    run("a, b, c = 1, 2")
+    run("a, b, c = f()")
+
+    check("max([f(),g()]) == 4")
+    check("'hello'[g()] == 'h'")
+    run("'guk%d' % h(f())")

py/_code/assertion.py

@@ -0,0 +1,75 @@
+import sys
+import py
+
+BuiltinAssertionError = py.builtin.builtins.AssertionError
+
+
+def _format_explanation(explanation):
+    # uck!  See CallFunc for where \n{ and \n} escape sequences are used
+    raw_lines = (explanation or '').split('\n')
+    # escape newlines not followed by { and }
+    lines = [raw_lines[0]]
+    for l in raw_lines[1:]:
+        if l.startswith('{') or l.startswith('}'):
+            lines.append(l)
+        else:
+            lines[-1] += '\\n' + l
+
+    result = lines[:1]
+    stack = [0]
+    stackcnt = [0]
+    for line in lines[1:]:
+        if line.startswith('{'):
+            if stackcnt[-1]:
+                s = 'and   '
+            else:
+                s = 'where '
+            stack.append(len(result))
+            stackcnt[-1] += 1
+            stackcnt.append(0)
+            result.append(' +' + '  '*(len(stack)-1) + s + line[1:])
+        else:
+            assert line.startswith('}')
+            stack.pop()
+            stackcnt.pop()
+            result[stack[-1]] += line[1:]
+    assert len(stack) == 1
+    return '\n'.join(result)
+
+
+if sys.version_info >= (2, 6) or (sys.platform.startswith("java")):
+    from py._code._assertionnew import interpret
+else:
+    from py._code._assertionold import interpret
+
+
+class AssertionError(BuiltinAssertionError):
+
+    def __init__(self, *args):
+        BuiltinAssertionError.__init__(self, *args)
+        if args:
+            try:
+                self.msg = str(args[0])
+            except (KeyboardInterrupt, SystemExit):
+                raise
+            except:
+                self.msg = "<[broken __repr__] %s at %0xd>" %(
+                    args[0].__class__, id(args[0]))
+        else:
+            f = py.code.Frame(sys._getframe(1))
+            try:
+                source = f.statement
+                source = str(source.deindent()).strip()
+            except py.error.ENOENT:
+                source = None
+                # this can also occur during reinterpretation, when the
+                # co_filename is set to "<run>".
+            if source:
+                self.msg = interpret(source, f, should_fail=True)
+                if not self.args:
+                    self.args = (self.msg,)
+            else:
+                self.msg = None
+
+if sys.version_info > (3, 0):
+    AssertionError.__module__ = "builtins"

py/_code/code.py

@@ -0,0 +1,768 @@
+import py
+import sys
+
+builtin_repr = repr
+
+repr = py.builtin._tryimport('repr', 'reprlib')
+
+class Code(object):
+    """ wrapper around Python code objects """
+    def __init__(self, rawcode):
+        rawcode = py.code.getrawcode(rawcode)
+        self.raw = rawcode 
+        try:
+            self.filename = rawcode.co_filename
+            self.firstlineno = rawcode.co_firstlineno - 1
+            self.name = rawcode.co_name
+        except AttributeError: 
+            raise TypeError("not a code object: %r" %(rawcode,))
+        
+    def __eq__(self, other): 
+        return self.raw == other.raw
+
+    def __ne__(self, other):
+        return not self == other
+
+    def new(self, rec=False, **kwargs): 
+        """ return new code object with modified attributes. 
+            if rec-cursive is true then dive into code 
+            objects contained in co_consts. 
+        """ 
+        if sys.platform.startswith("java"):
+            # XXX jython does not support the below co_filename hack
+            return self.raw 
+        names = [x for x in dir(self.raw) if x[:3] == 'co_']
+        for name in kwargs: 
+            if name not in names: 
+                raise TypeError("unknown code attribute: %r" %(name, ))
+        if rec and hasattr(self.raw, 'co_consts'):  # jython 
+            newconstlist = []
+            co = self.raw
+            cotype = type(co)
+            for c in co.co_consts:
+                if isinstance(c, cotype):
+                    c = self.__class__(c).new(rec=True, **kwargs) 
+                newconstlist.append(c)
+            return self.new(rec=False, co_consts=tuple(newconstlist), **kwargs) 
+        for name in names:
+            if name not in kwargs:
+                kwargs[name] = getattr(self.raw, name)
+        arglist = [
+                 kwargs['co_argcount'],
+                 kwargs['co_nlocals'],
+                 kwargs.get('co_stacksize', 0), # jython
+                 kwargs.get('co_flags', 0), # jython
+                 kwargs.get('co_code', ''), # jython
+                 kwargs.get('co_consts', ()), # jython
+                 kwargs.get('co_names', []), # 
+                 kwargs['co_varnames'],
+                 kwargs['co_filename'],
+                 kwargs['co_name'],
+                 kwargs['co_firstlineno'],
+                 kwargs.get('co_lnotab', ''), #jython
+                 kwargs.get('co_freevars', None), #jython
+                 kwargs.get('co_cellvars', None), # jython
+        ]
+        if sys.version_info >= (3,0):
+            arglist.insert(1, kwargs['co_kwonlyargcount'])
+            return self.raw.__class__(*arglist)
+        else:
+            return py.std.new.code(*arglist)
+
+    def path(self):
+        """ return a py.path.local object pointing to the source code """
+        fn = self.raw.co_filename 
+        try:
+            return fn.__path__
+        except AttributeError:
+            p = py.path.local(self.raw.co_filename)
+            if not p.check(file=1):
+                # XXX maybe try harder like the weird logic 
+                # in the standard lib [linecache.updatecache] does? 
+                p = self.raw.co_filename
+            return p
+                
+    path = property(path, None, None, "path of this code object")
+
+    def fullsource(self):
+        """ return a py.code.Source object for the full source file of the code
+        """
+        from py._code import source
+        full, _ = source.findsource(self.raw)
+        return full
+    fullsource = property(fullsource, None, None,
+                          "full source containing this code object")
+    
+    def source(self):
+        """ return a py.code.Source object for the code object's source only
+        """
+        # return source only for that part of code
+        return py.code.Source(self.raw)
+
+    def getargs(self):
+        """ return a tuple with the argument names for the code object
+        """
+        # handfull shortcut for getting args
+        raw = self.raw
+        return raw.co_varnames[:raw.co_argcount]
+
+class Frame(object):
+    """Wrapper around a Python frame holding f_locals and f_globals
+    in which expressions can be evaluated."""
+
+    def __init__(self, frame):
+        self.code = py.code.Code(frame.f_code)
+        self.lineno = frame.f_lineno - 1
+        self.f_globals = frame.f_globals
+        self.f_locals = frame.f_locals
+        self.raw = frame
+
+    def statement(self):
+        if self.code.fullsource is None:
+            return py.code.Source("")
+        return self.code.fullsource.getstatement(self.lineno)
+    statement = property(statement, None, None,
+                         "statement this frame is at")
+
+    def eval(self, code, **vars):
+        """ evaluate 'code' in the frame
+
+            'vars' are optional additional local variables
+
+            returns the result of the evaluation
+        """
+        f_locals = self.f_locals.copy() 
+        f_locals.update(vars)
+        return eval(code, self.f_globals, f_locals)
+
+    def exec_(self, code, **vars):
+        """ exec 'code' in the frame
+
+            'vars' are optiona; additional local variables
+        """
+        f_locals = self.f_locals.copy() 
+        f_locals.update(vars)
+        py.builtin.exec_(code, self.f_globals, f_locals )
+
+    def repr(self, object):
+        """ return a 'safe' (non-recursive, one-line) string repr for 'object'
+        """
+        return safe_repr(object)
+
+    def is_true(self, object):
+        return object
+
+    def getargs(self):
+        """ return a list of tuples (name, value) for all arguments
+        """
+        retval = []
+        for arg in self.code.getargs():
+            try:
+                retval.append((arg, self.f_locals[arg]))
+            except KeyError:
+                pass     # this can occur when using Psyco
+        return retval
+
+class TracebackEntry(object):
+    """ a single entry in a traceback """
+    
+    exprinfo = None 
+
+    def __init__(self, rawentry):
+        self._rawentry = rawentry
+        self.frame = py.code.Frame(rawentry.tb_frame)
+        # Ugh. 2.4 and 2.5 differs here when encountering
+        # multi-line statements. Not sure about the solution, but
+        # should be portable
+        self.lineno = rawentry.tb_lineno - 1
+        self.relline = self.lineno - self.frame.code.firstlineno
+
+    def __repr__(self):
+        return "<TracebackEntry %s:%d>" %(self.frame.code.path, self.lineno+1)
+
+    def statement(self):
+        """ return a py.code.Source object for the current statement """
+        source = self.frame.code.fullsource
+        return source.getstatement(self.lineno)
+    statement = property(statement, None, None,
+                         "statement of this traceback entry.")
+
+    def path(self):
+        return self.frame.code.path
+    path = property(path, None, None, "path to the full source code")
+
+    def getlocals(self):
+        return self.frame.f_locals
+    locals = property(getlocals, None, None, "locals of underlaying frame")
+
+    def reinterpret(self):
+        """Reinterpret the failing statement and returns a detailed information
+           about what operations are performed."""
+        if self.exprinfo is None:
+            from py._code import assertion 
+            source = str(self.statement).strip()
+            x = assertion.interpret(source, self.frame, should_fail=True)
+            if not isinstance(x, str):
+                raise TypeError("interpret returned non-string %r" % (x,))
+            self.exprinfo = x 
+        return self.exprinfo
+
+    def getfirstlinesource(self):
+        return self.frame.code.firstlineno
+
+    def getsource(self): 
+        """ return failing source code. """
+        source = self.frame.code.fullsource
+        if source is None:
+            return None
+        start = self.getfirstlinesource()
+        end = self.lineno
+        try:
+            _, end = source.getstatementrange(end) 
+        except IndexError: 
+            end = self.lineno + 1 
+        # heuristic to stop displaying source on e.g. 
+        #   if something:  # assume this causes a NameError
+        #      # _this_ lines and the one 
+               #        below we don't want from entry.getsource() 
+        for i in range(self.lineno, end): 
+            if source[i].rstrip().endswith(':'): 
+                end = i + 1
+                break 
+        return source[start:end]
+    source = property(getsource)
+
+    def ishidden(self):
+        """ return True if the current frame has a var __tracebackhide__ 
+            resolving to True
+            
+            mostly for internal use
+        """
+        try: 
+            return self.frame.eval("__tracebackhide__") 
+        except (SystemExit, KeyboardInterrupt): 
+            raise
+        except:
+            return False 
+
+    def __str__(self): 
+        try: 
+            fn = str(self.path) 
+        except py.error.Error: 
+            fn = '???'
+        name = self.frame.code.name 
+        try: 
+            line = str(self.statement).lstrip()
+        except KeyboardInterrupt:
+            raise
+        except:
+            line = "???"
+        return "  File %r:%d in %s\n  %s\n" %(fn, self.lineno+1, name, line) 
+
+    def name(self):
+        return self.frame.code.raw.co_name
+    name = property(name, None, None, "co_name of underlaying code")
+
+class Traceback(list):
+    """ Traceback objects encapsulate and offer higher level 
+        access to Traceback entries.  
+    """
+    Entry = TracebackEntry 
+    def __init__(self, tb):
+        """ initialize from given python traceback object. """
+        if hasattr(tb, 'tb_next'):
+            def f(cur): 
+                while cur is not None: 
+                    yield self.Entry(cur)
+                    cur = cur.tb_next 
+            list.__init__(self, f(tb)) 
+        else:
+            list.__init__(self, tb)
+
+    def cut(self, path=None, lineno=None, firstlineno=None, excludepath=None):
+        """ return a Traceback instance wrapping part of this Traceback
+
+            by provding any combination of path, lineno and firstlineno, the
+            first frame to start the to-be-returned traceback is determined
+
+            this allows cutting the first part of a Traceback instance e.g.
+            for formatting reasons (removing some uninteresting bits that deal
+            with handling of the exception/traceback)
+        """
+        for x in self:
+            code = x.frame.code
+            codepath = code.path
+            if ((path is None or codepath == path) and
+                (excludepath is None or (hasattr(codepath, 'relto') and
+                 not codepath.relto(excludepath))) and 
+                (lineno is None or x.lineno == lineno) and
+                (firstlineno is None or x.frame.code.firstlineno == firstlineno)):
+                return Traceback(x._rawentry)
+        return self
+
+    def __getitem__(self, key):
+        val = super(Traceback, self).__getitem__(key)
+        if isinstance(key, type(slice(0))):
+            val = self.__class__(val)
+        return val
+
+    def filter(self, fn=lambda x: not x.ishidden()):
+        """ return a Traceback instance with certain items removed
+
+            fn is a function that gets a single argument, a TracebackItem
+            instance, and should return True when the item should be added
+            to the Traceback, False when not
+
+            by default this removes all the TracebackItems which are hidden
+            (see ishidden() above)
+        """
+        return Traceback(filter(fn, self))
+
+    def getcrashentry(self):
+        """ return last non-hidden traceback entry that lead
+        to the exception of a traceback. 
+        """
+        tb = self.filter()
+        if not tb:
+            tb = self
+        return tb[-1]
+
+    def recursionindex(self):
+        """ return the index of the frame/TracebackItem where recursion
+            originates if appropriate, None if no recursion occurred
+        """
+        cache = {}
+        for i, entry in enumerate(self):
+            key = entry.frame.code.path, entry.lineno 
+            #print "checking for recursion at", key
+            l = cache.setdefault(key, [])
+            if l: 
+                f = entry.frame
+                loc = f.f_locals
+                for otherloc in l: 
+                    if f.is_true(f.eval(co_equal, 
+                        __recursioncache_locals_1=loc,
+                        __recursioncache_locals_2=otherloc)):
+                        return i 
+            l.append(entry.frame.f_locals)
+        return None
+
+co_equal = compile('__recursioncache_locals_1 == __recursioncache_locals_2',
+                   '?', 'eval')
+
+class ExceptionInfo(object):
+    """ wraps sys.exc_info() objects and offers
+        help for navigating the traceback.
+    """
+    _striptext = '' 
+    def __init__(self, tup=None, exprinfo=None):
+        # NB. all attributes are private!  Subclasses or other
+        #     ExceptionInfo-like classes may have different attributes.
+        if tup is None:
+            tup = sys.exc_info()
+            if exprinfo is None and isinstance(tup[1], py.code._AssertionError):
+                exprinfo = getattr(tup[1], 'msg', None)
+                if exprinfo is None:
+                    exprinfo = str(tup[1])
+                if exprinfo and exprinfo.startswith('assert '):
+                    self._striptext = 'AssertionError: '
+        self._excinfo = tup
+        self.type, self.value, tb = self._excinfo
+        self.typename = self.type.__name__
+        self.traceback = py.code.Traceback(tb) 
+
+    def __repr__(self):
+        return "<ExceptionInfo %s tblen=%d>" % (self.typename, len(self.traceback))
+
+    def exconly(self, tryshort=False): 
+        """ return the exception as a string
+        
+            when 'tryshort' resolves to True, and the exception is a
+            py.code._AssertionError, only the actual exception part of
+            the exception representation is returned (so 'AssertionError: ' is
+            removed from the beginning)
+        """
+        lines = py.std.traceback.format_exception_only(self.type, self.value)
+        text = ''.join(lines)
+        text = text.rstrip()
+        if tryshort: 
+            if text.startswith(self._striptext): 
+                text = text[len(self._striptext):]
+        return text
+
+    def errisinstance(self, exc): 
+        """ return True if the exception is an instance of exc """
+        return isinstance(self.value, exc) 
+
+    def _getreprcrash(self):
+        exconly = self.exconly(tryshort=True)
+        entry = self.traceback.getcrashentry()
+        path, lineno = entry.path, entry.lineno
+        reprcrash = ReprFileLocation(path, lineno+1, exconly)
+        return reprcrash
+
+    def getrepr(self, showlocals=False, style="long", 
+            abspath=False, tbfilter=True, funcargs=False):
+        """ return str()able representation of this exception info.
+            showlocals: show locals per traceback entry 
+            style: long|short|no traceback style 
+            tbfilter: hide entries (where __tracebackhide__ is true)
+        """
+        fmt = FormattedExcinfo(showlocals=showlocals, style=style, 
+            abspath=abspath, tbfilter=tbfilter, funcargs=funcargs)
+        return fmt.repr_excinfo(self)
+
+    def __str__(self):
+        entry = self.traceback[-1]
+        loc = ReprFileLocation(entry.path, entry.lineno + 1, self.exconly())
+        return str(loc)
+
+class FormattedExcinfo(object):
+    """ presenting information about failing Functions and Generators. """ 
+    # for traceback entries 
+    flow_marker = ">"    
+    fail_marker = "E"
+    
+    def __init__(self, showlocals=False, style="long", abspath=True, tbfilter=True, funcargs=False):
+        self.showlocals = showlocals
+        self.style = style
+        self.tbfilter = tbfilter
+        self.funcargs = funcargs
+        self.abspath = abspath 
+
+    def _getindent(self, source):
+        # figure out indent for given source 
+        try:
+            s = str(source.getstatement(len(source)-1))
+        except KeyboardInterrupt: 
+            raise 
+        except:
+            try:
+                s = str(source[-1])
+            except KeyboardInterrupt:
+                raise
+            except:
+                return 0
+        return 4 + (len(s) - len(s.lstrip()))
+
+    def _getentrysource(self, entry):
+        source = entry.getsource()
+        if source is not None:
+            source = source.deindent()
+        return source
+    
+    def _saferepr(self, obj):
+        return safe_repr(obj)
+
+    def repr_args(self, entry):
+        if self.funcargs:
+            args = []
+            for argname, argvalue in entry.frame.getargs():
+                args.append((argname, self._saferepr(argvalue)))
+            return ReprFuncArgs(args)
+
+    def get_source(self, source, line_index=-1, excinfo=None):
+        """ return formatted and marked up source lines. """
+        lines = []
+        if source is None:
+            source = py.code.Source("???")
+            line_index = 0 
+        if line_index < 0:
+            line_index += len(source)
+        for i in range(len(source)):
+            if i == line_index:
+                prefix = self.flow_marker + "   "
+            else:
+                prefix = "    "
+            line = prefix + source[i]
+            lines.append(line)
+        if excinfo is not None:
+            indent = self._getindent(source)
+            lines.extend(self.get_exconly(excinfo, indent=indent, markall=True))
+        return lines
+
+    def get_exconly(self, excinfo, indent=4, markall=False):
+        lines = []
+        indent = " " * indent 
+        # get the real exception information out 
+        exlines = excinfo.exconly(tryshort=True).split('\n')
+        failindent = self.fail_marker + indent[1:]
+        for line in exlines:
+            lines.append(failindent + line)
+            if not markall:
+                failindent = indent 
+        return lines
+
+    def repr_locals(self, locals):
+        if self.showlocals: 
+            lines = []
+            keys = list(locals)
+            keys.sort()
+            for name in keys:
+                value = locals[name]
+                if name == '__builtins__': 
+                    lines.append("__builtins__ = <builtins>")
+                else:
+                    # This formatting could all be handled by the
+                    # _repr() function, which is only repr.Repr in
+                    # disguise, so is very configurable.
+                    str_repr = self._saferepr(value)
+                    #if len(str_repr) < 70 or not isinstance(value,
+                    #                            (list, tuple, dict)):
+                    lines.append("%-10s = %s" %(name, str_repr))
+                    #else:
+                    #    self._line("%-10s =\\" % (name,))
+                    #    # XXX
+                    #    py.std.pprint.pprint(value, stream=self.excinfowriter)
+            return ReprLocals(lines)
+
+    def repr_traceback_entry(self, entry, excinfo=None):
+        # excinfo is not None if this is the last tb entry 
+        source = self._getentrysource(entry)
+        if source is None:
+            source = py.code.Source("???")
+            line_index = 0
+        else:
+            line_index = entry.lineno - entry.getfirstlinesource()
+
+        lines = []
+        if self.style == "long":
+            reprargs = self.repr_args(entry) 
+            lines.extend(self.get_source(source, line_index, excinfo))
+            message = excinfo and excinfo.typename or ""
+            path = self._makepath(entry.path)
+            filelocrepr = ReprFileLocation(path, entry.lineno+1, message)
+            localsrepr =  self.repr_locals(entry.locals)
+            return ReprEntry(lines, reprargs, localsrepr, filelocrepr)
+        else: 
+            if self.style == "short":
+                line = source[line_index].lstrip()
+                trybasename = getattr(entry.path, 'basename', entry.path)
+                lines.append('  File "%s", line %d, in %s' % (
+                    trybasename, entry.lineno+1, entry.name))
+                lines.append("    " + line) 
+            if excinfo: 
+                lines.extend(self.get_exconly(excinfo, indent=4))
+            return ReprEntry(lines, None, None, None)
+
+    def _makepath(self, path):
+        if not self.abspath:
+            np = py.path.local().bestrelpath(path)
+            if len(np) < len(str(path)):
+                path = np
+        return path
+
+    def repr_traceback(self, excinfo): 
+        traceback = excinfo.traceback 
+        if self.tbfilter:
+            traceback = traceback.filter()
+        recursionindex = None
+        if excinfo.errisinstance(RuntimeError):
+            recursionindex = traceback.recursionindex()
+        last = traceback[-1]
+        entries = []
+        extraline = None
+        for index, entry in enumerate(traceback): 
+            einfo = (last == entry) and excinfo or None
+            reprentry = self.repr_traceback_entry(entry, einfo)
+            entries.append(reprentry)
+            if index == recursionindex:
+                extraline = "!!! Recursion detected (same locals & position)"
+                break
+        return ReprTraceback(entries, extraline, style=self.style)
+
+    def repr_excinfo(self, excinfo):
+        reprtraceback = self.repr_traceback(excinfo)
+        reprcrash = excinfo._getreprcrash()
+        return ReprExceptionInfo(reprtraceback, reprcrash)
+
+class TerminalRepr:
+    def __str__(self):
+        tw = py.io.TerminalWriter(stringio=True)
+        self.toterminal(tw)
+        return tw.stringio.getvalue().strip()
+
+    def __repr__(self):
+        return "<%s instance at %0x>" %(self.__class__, id(self))
+
+class ReprExceptionInfo(TerminalRepr):
+    def __init__(self, reprtraceback, reprcrash):
+        self.reprtraceback = reprtraceback
+        self.reprcrash = reprcrash 
+        self.sections = []
+
+    def addsection(self, name, content, sep="-"):
+        self.sections.append((name, content, sep))
+
+    def toterminal(self, tw):
+        self.reprtraceback.toterminal(tw)
+        for name, content, sep in self.sections:
+            tw.sep(sep, name)
+            tw.line(content)
+    
+class ReprTraceback(TerminalRepr):
+    entrysep = "_ "
+
+    def __init__(self, reprentries, extraline, style):
+        self.reprentries = reprentries
+        self.extraline = extraline
+        self.style = style
+
+    def toterminal(self, tw):
+        sepok = False 
+        for entry in self.reprentries:
+            if self.style == "long":
+                if sepok:
+                    tw.sep(self.entrysep)
+                tw.line("")
+            sepok = True
+            entry.toterminal(tw)
+        if self.extraline:
+            tw.line(self.extraline)
+
+class ReprEntry(TerminalRepr):
+    localssep = "_ "
+
+    def __init__(self, lines, reprfuncargs, reprlocals, filelocrepr):
+        self.lines = lines
+        self.reprfuncargs = reprfuncargs
+        self.reprlocals = reprlocals 
+        self.reprfileloc = filelocrepr
+
+    def toterminal(self, tw):
+        if self.reprfuncargs:
+            self.reprfuncargs.toterminal(tw)
+        for line in self.lines:
+            red = line.startswith("E   ") 
+            tw.line(line, bold=True, red=red)
+        if self.reprlocals:
+            #tw.sep(self.localssep, "Locals")
+            tw.line("")
+            self.reprlocals.toterminal(tw)
+        if self.reprfileloc:
+            tw.line("")
+            self.reprfileloc.toterminal(tw)
+
+    def __str__(self):
+        return "%s\n%s\n%s" % ("\n".join(self.lines), 
+                               self.reprlocals, 
+                               self.reprfileloc)
+
+class ReprFileLocation(TerminalRepr):
+    def __init__(self, path, lineno, message):
+        self.path = str(path)
+        self.lineno = lineno
+        self.message = message
+
+    def toterminal(self, tw):
+        # filename and lineno output for each entry,
+        # using an output format that most editors unterstand
+        msg = self.message 
+        i = msg.find("\n")
+        if i != -1:
+            msg = msg[:i] 
+        tw.line("%s:%s: %s" %(self.path, self.lineno, msg))
+
+class ReprLocals(TerminalRepr):
+    def __init__(self, lines):
+        self.lines = lines 
+
+    def toterminal(self, tw):
+        for line in self.lines:
+            tw.line(line)
+
+class ReprFuncArgs(TerminalRepr):
+    def __init__(self, args):
+        self.args = args
+
+    def toterminal(self, tw):
+        if self.args:
+            linesofar = ""
+            for name, value in self.args:
+                ns = "%s = %s" %(name, value)
+                if len(ns) + len(linesofar) + 2 > tw.fullwidth:
+                    if linesofar:
+                        tw.line(linesofar)
+                    linesofar =  ns 
+                else:
+                    if linesofar:
+                        linesofar += ", " + ns
+                    else:
+                        linesofar = ns
+            if linesofar:
+                tw.line(linesofar)
+            tw.line("")
+
+
+
+class SafeRepr(repr.Repr):
+    """ subclass of repr.Repr that limits the resulting size of repr() 
+        and includes information on exceptions raised during the call. 
+    """ 
+    def __init__(self, *args, **kwargs):
+        repr.Repr.__init__(self, *args, **kwargs)
+        self.maxstring = 240   # 3 * 80 chars
+        self.maxother = 160    # 2 * 80 chars
+
+    def repr(self, x):
+        return self._callhelper(repr.Repr.repr, self, x)
+
+    def repr_instance(self, x, level):
+        return self._callhelper(builtin_repr, x)
+        
+    def _callhelper(self, call, x, *args):
+        try:
+            # Try the vanilla repr and make sure that the result is a string
+            s = call(x, *args)
+        except (KeyboardInterrupt, MemoryError, SystemExit):
+            raise
+        except:
+            cls, e, tb = sys.exc_info()
+            try:
+                exc_name = cls.__name__
+            except:
+                exc_name = 'unknown'
+            try:
+                exc_info = str(e)
+            except:
+                exc_info = 'unknown'
+            return '<[%s("%s") raised in repr()] %s object at 0x%x>' % (
+                exc_name, exc_info, x.__class__.__name__, id(x))
+        else:
+            if len(s) > self.maxstring:
+                i = max(0, (self.maxstring-3)//2)
+                j = max(0, self.maxstring-3-i)
+                s = s[:i] + '...' + s[len(s)-j:]
+            return s
+
+safe_repr = SafeRepr().repr
+
+oldbuiltins = {}
+
+def patch_builtins(assertion=True, compile=True):
+    """ put compile and AssertionError builtins to Python's builtins. """
+    if assertion:
+        from py._code import assertion
+        l = oldbuiltins.setdefault('AssertionError', [])
+        l.append(py.builtin.builtins.AssertionError)
+        py.builtin.builtins.AssertionError = assertion.AssertionError
+    if compile: 
+        l = oldbuiltins.setdefault('compile', [])
+        l.append(py.builtin.builtins.compile)
+        py.builtin.builtins.compile = py.code.compile
+
+def unpatch_builtins(assertion=True, compile=True):
+    """ remove compile and AssertionError builtins from Python builtins. """
+    if assertion:
+        py.builtin.builtins.AssertionError = oldbuiltins['AssertionError'].pop()
+    if compile: 
+        py.builtin.builtins.compile = oldbuiltins['compile'].pop()
+
+def getrawcode(obj):
+    """ return code object for given function. """ 
+    obj = getattr(obj, 'im_func', obj)
+    obj = getattr(obj, 'func_code', obj)
+    obj = getattr(obj, 'f_code', obj)
+    obj = getattr(obj, '__code__', obj)
+    return obj
+    

py/_code/oldmagic.py

@@ -0,0 +1,62 @@
+""" deprecated module for turning on/off some features. """ 
+
+import py 
+
+from py.builtin import builtins as cpy_builtin
+
+def invoke(assertion=False, compile=False):
+    """ (deprecated) invoke magic, currently you can specify:
+
+        assertion  patches the builtin AssertionError to try to give
+                   more meaningful AssertionErrors, which by means
+                   of deploying a mini-interpreter constructs
+                   a useful error message.
+    """
+    py.log._apiwarn("1.1", 
+        "py.magic.invoke() is deprecated, use py.code.patch_builtins()",
+        stacklevel=2, 
+    )
+    py.code.patch_builtins(assertion=assertion, compile=compile)
+
+def revoke(assertion=False, compile=False):
+    """ (deprecated) revoke previously invoked magic (see invoke())."""
+    py.log._apiwarn("1.1", 
+        "py.magic.revoke() is deprecated, use py.code.unpatch_builtins()",
+        stacklevel=2, 
+    )
+    py.code.unpatch_builtins(assertion=assertion, compile=compile)
+
+patched = {}
+
+def patch(namespace, name, value):
+    """ (deprecated) rebind the 'name' on the 'namespace'  to the 'value',
+        possibly and remember the original value. Multiple
+        invocations to the same namespace/name pair will
+        remember a list of old values.
+    """
+    py.log._apiwarn("1.1", 
+        "py.magic.patch() is deprecated, in tests use monkeypatch funcarg.", 
+        stacklevel=2, 
+    )
+    nref = (namespace, name)
+    orig = getattr(namespace, name)
+    patched.setdefault(nref, []).append(orig)
+    setattr(namespace, name, value)
+    return orig
+
+def revert(namespace, name):
+    """ (deprecated) revert to the orginal value the last patch modified.
+        Raise ValueError if no such original value exists.
+    """
+    py.log._apiwarn("1.1", 
+        "py.magic.revert() is deprecated, in tests use monkeypatch funcarg.",
+        stacklevel=2, 
+    )
+    nref = (namespace, name)
+    if nref not in patched or not patched[nref]:
+        raise ValueError("No original value stored for %s.%s" % nref)
+    current = getattr(namespace, name)
+    orig = patched[nref].pop()
+    setattr(namespace, name, orig)
+    return current
+

py/_code/oldmagic2.py

@@ -0,0 +1,6 @@
+
+import py
+
+py.log._apiwarn("1.1", "py.magic.AssertionError is deprecated, use py.code._AssertionError", stacklevel=2)
+
+from py.code import _AssertionError as AssertionError

py/_code/source.py

@@ -0,0 +1,347 @@
+from __future__ import generators
+import sys
+import inspect, tokenize
+import py
+cpy_compile = compile 
+
+try:
+    import _ast
+    from _ast import PyCF_ONLY_AST as _AST_FLAG
+except ImportError:
+    _AST_FLAG = 0
+    _ast = None
+
+
+class Source(object):
+    """ a immutable object holding a source code fragment,
+        possibly deindenting it.
+    """
+    def __init__(self, *parts, **kwargs):
+        self.lines = lines = []
+        de = kwargs.get('deindent', True)
+        rstrip = kwargs.get('rstrip', True) 
+        for part in parts:
+            if not part: 
+                partlines = []
+            if isinstance(part, Source):
+                partlines = part.lines
+            elif isinstance(part, py.builtin._basestring):
+                partlines = part.split('\n')
+                if rstrip:
+                    while partlines: 
+                        if partlines[-1].strip(): 
+                            break
+                        partlines.pop()
+            else:
+                partlines = getsource(part, deindent=de).lines
+            if de:
+                partlines = deindent(partlines)
+            lines.extend(partlines)
+
+    def __eq__(self, other): 
+        try:
+            return self.lines == other.lines 
+        except AttributeError: 
+            if isinstance(other, str): 
+                return str(self) == other 
+            return False 
+
+    def __getitem__(self, key):
+        if isinstance(key, int):
+            return self.lines[key]
+        else:
+            if key.step not in (None, 1):
+                raise IndexError("cannot slice a Source with a step")
+            return self.__getslice__(key.start, key.stop)
+
+    def __len__(self): 
+        return len(self.lines) 
+
+    def __getslice__(self, start, end):
+        newsource = Source()
+        newsource.lines = self.lines[start:end]
+        return newsource
+
+    def strip(self):
+        """ return new source object with trailing
+            and leading blank lines removed.
+        """
+        start, end = 0, len(self)
+        while start < end and not self.lines[start].strip():
+            start += 1
+        while end > start and not self.lines[end-1].strip():
+            end -= 1
+        source = Source()
+        source.lines[:] = self.lines[start:end]
+        return source
+
+    def putaround(self, before='', after='', indent=' ' * 4): 
+        """ return a copy of the source object with 
+            'before' and 'after' wrapped around it. 
+        """
+        before = Source(before)
+        after = Source(after)
+        newsource = Source()
+        lines = [ (indent + line) for line in self.lines]
+        newsource.lines = before.lines + lines +  after.lines
+        return newsource
+
+    def indent(self, indent=' ' * 4): 
+        """ return a copy of the source object with 
+            all lines indented by the given indent-string. 
+        """
+        newsource = Source()
+        newsource.lines = [(indent+line) for line in self.lines]
+        return newsource
+
+    def getstatement(self, lineno):
+        """ return Source statement which contains the
+            given linenumber (counted from 0).
+        """
+        start, end = self.getstatementrange(lineno)
+        return self[start:end]
+
+    def getstatementrange(self, lineno):
+        """ return (start, end) tuple which spans the minimal 
+            statement region which containing the given lineno.
+        """
+        # XXX there must be a better than these heuristic ways ...
+        # XXX there may even be better heuristics :-)
+        if not (0 <= lineno < len(self)):
+            raise IndexError("lineno out of range")
+
+        # 1. find the start of the statement
+        from codeop import compile_command
+        for start in range(lineno, -1, -1):
+            trylines = self.lines[start:lineno+1]
+            # quick hack to indent the source and get it as a string in one go
+            trylines.insert(0, 'def xxx():')
+            trysource = '\n '.join(trylines)
+            #              ^ space here
+            try:
+                compile_command(trysource)
+            except (SyntaxError, OverflowError, ValueError):
+                pass
+            else:
+                break   # got a valid or incomplete statement
+
+        # 2. find the end of the statement
+        for end in range(lineno+1, len(self)+1):
+            trysource = self[start:end]
+            if trysource.isparseable():
+                break
+
+        return start, end
+
+    def getblockend(self, lineno):
+        # XXX
+        lines = [x + '\n' for x in self.lines[lineno:]]
+        blocklines = inspect.getblock(lines)
+        #print blocklines
+        return lineno + len(blocklines) - 1
+
+    def deindent(self, offset=None):
+        """ return a new source object deindented by offset.
+            If offset is None then guess an indentation offset from
+            the first non-blank line.  Subsequent lines which have a
+            lower indentation offset will be copied verbatim as
+            they are assumed to be part of multilines.
+        """
+        # XXX maybe use the tokenizer to properly handle multiline
+        #     strings etc.pp?
+        newsource = Source()
+        newsource.lines[:] = deindent(self.lines, offset)
+        return newsource
+
+    def isparseable(self, deindent=True):
+        """ return True if source is parseable, heuristically
+            deindenting it by default. 
+        """
+        try:
+            import parser
+        except ImportError:
+            syntax_checker = lambda x: compile(x, 'asd', 'exec')
+        else:
+            syntax_checker = parser.suite
+    
+        if deindent:
+            source = str(self.deindent())
+        else:
+            source = str(self)
+        try:
+            #compile(source+'\n', "x", "exec")
+            syntax_checker(source+'\n')
+        except SyntaxError:
+            return False
+        else:
+            return True
+
+    def __str__(self):
+        return "\n".join(self.lines)
+
+    def compile(self, filename=None, mode='exec', 
+                flag=generators.compiler_flag, 
+                dont_inherit=0, _genframe=None):
+        """ return compiled code object. if filename is None
+            invent an artificial filename which displays
+            the source/line position of the caller frame.
+        """
+        if not filename or py.path.local(filename).check(file=0): 
+            if _genframe is None:
+                _genframe = sys._getframe(1) # the caller
+            fn,lineno = _genframe.f_code.co_filename, _genframe.f_lineno
+            if not filename:
+                filename = '<codegen %s:%d>' % (fn, lineno)
+            else:
+                filename = '<codegen %r %s:%d>' % (filename, fn, lineno)
+        source = "\n".join(self.lines) + '\n'
+        try:
+            co = cpy_compile(source, filename, mode, flag)
+        except SyntaxError:
+            ex = sys.exc_info()[1]
+            # re-represent syntax errors from parsing python strings
+            msglines = self.lines[:ex.lineno]
+            if ex.offset:
+                msglines.append(" "*ex.offset + '^')
+            msglines.append("syntax error probably generated here: %s" % filename)
+            newex = SyntaxError('\n'.join(msglines))
+            newex.offset = ex.offset
+            newex.lineno = ex.lineno
+            newex.text = ex.text
+            raise newex
+        else:
+            if flag & _AST_FLAG:
+                return co
+            co_filename = MyStr(filename)
+            co_filename.__source__ = self
+            return py.code.Code(co).new(rec=1, co_filename=co_filename) 
+            #return newcode_withfilename(co, co_filename)
+
+#
+# public API shortcut functions
+#
+
+def compile_(source, filename=None, mode='exec', flags=
+            generators.compiler_flag, dont_inherit=0):
+    """ compile the given source to a raw code object,
+        which points back to the source code through
+        "co_filename.__source__".  All code objects
+        contained in the code object will recursively
+        also have this special subclass-of-string
+        filename.
+    """
+    if _ast is not None and isinstance(source, _ast.AST):
+        # XXX should Source support having AST?
+        return cpy_compile(source, filename, mode, flags, dont_inherit)
+    _genframe = sys._getframe(1) # the caller
+    s = Source(source)
+    co = s.compile(filename, mode, flags, _genframe=_genframe)
+    return co
+
+
+def getfslineno(obj):
+    try:
+        code = py.code.Code(obj)
+    except TypeError:
+        # fallback to 
+        fn = (py.std.inspect.getsourcefile(obj) or
+              py.std.inspect.getfile(obj))
+        fspath = fn and py.path.local(fn) or None
+        if fspath:
+            try:
+                _, lineno = findsource(obj)
+            except IOError:
+                lineno = None
+        else:
+            lineno = None
+    else:
+        fspath = code.path
+        lineno = code.firstlineno 
+    return fspath, lineno
+
+#
+# helper functions
+#
+class MyStr(str):
+    """ custom string which allows to add attributes. """
+
+def findsource(obj):
+    obj = py.code.getrawcode(obj)
+    try:
+        fullsource = obj.co_filename.__source__
+    except AttributeError:
+        try:
+            sourcelines, lineno = py.std.inspect.findsource(obj)
+        except (KeyboardInterrupt, SystemExit):
+            raise
+        except:
+            return None, None
+        source = Source()
+        source.lines = [line.rstrip() for line in sourcelines]
+        return source, lineno
+    else:
+        lineno = obj.co_firstlineno - 1        
+        return fullsource, lineno
+
+
+def getsource(obj, **kwargs):
+    obj = py.code.getrawcode(obj)
+    try:
+        fullsource = obj.co_filename.__source__
+    except AttributeError:
+        try:
+            strsrc = inspect.getsource(obj)
+        except IndentationError:
+            strsrc = "\"Buggy python version consider upgrading, cannot get source\""
+        assert isinstance(strsrc, str)
+        return Source(strsrc, **kwargs)
+    else:
+        lineno = obj.co_firstlineno - 1
+        end = fullsource.getblockend(lineno)
+        return Source(fullsource[lineno:end+1], deident=True)
+
+
+def deindent(lines, offset=None):
+    if offset is None:
+        for line in lines:
+            line = line.expandtabs()
+            s = line.lstrip()
+            if s:
+                offset = len(line)-len(s)
+                break
+        else:
+            offset = 0
+    if offset == 0:
+        return list(lines)
+    newlines = []
+    def readline_generator(lines):
+        for line in lines:
+            yield line + '\n'
+        while True:
+            yield ''
+        
+    r = readline_generator(lines)
+    try: 
+        readline = r.next
+    except AttributeError:
+        readline = r.__next__
+
+    try:
+        for _, _, (sline, _), (eline, _), _ in tokenize.generate_tokens(readline):
+            if sline > len(lines):
+                break # End of input reached
+            if sline > len(newlines):
+                line = lines[sline - 1].expandtabs()
+                if line.lstrip() and line[:offset].isspace():
+                    line = line[offset:] # Deindent
+                newlines.append(line)
+
+            for i in range(sline, eline):
+                # Don't deindent continuing lines of
+                # multiline tokens (i.e. multiline strings)
+                newlines.append(lines[i])
+    except (IndentationError, tokenize.TokenError):
+        pass
+    # Add any lines we didn't see. E.g. if an exception was raised.
+    newlines.extend(lines[len(newlines):])
+    return newlines