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This commit is contained in:
Ronny Pfannschmidt
2018-05-26 09:05:41 +02:00
parent ee6c54904b
commit eaa882f3d5
50 changed files with 10 additions and 5 deletions
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151
src/_pytest/assertion/__init__.py Normal file
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"""
support for presenting detailed information in failing assertions.
"""
from __future__ import absolute_import, division, print_function
import sys
import six
from _pytest.assertion import util
from _pytest.assertion import rewrite
from _pytest.assertion import truncate
def pytest_addoption(parser):
group = parser.getgroup("debugconfig")
group.addoption(
"--assert",
action="store",
dest="assertmode",
choices=("rewrite", "plain"),
default="rewrite",
metavar="MODE",
help="""Control assertion debugging tools. 'plain'
performs no assertion debugging. 'rewrite'
(the default) rewrites assert statements in
test modules on import to provide assert
expression information.""",
)
def register_assert_rewrite(*names):
"""Register one or more module names to be rewritten on import.
This function will make sure that this module or all modules inside
the package will get their assert statements rewritten.
Thus you should make sure to call this before the module is
actually imported, usually in your __init__.py if you are a plugin
using a package.
:raise TypeError: if the given module names are not strings.
"""
for name in names:
if not isinstance(name, str):
msg = "expected module names as *args, got {0} instead"
raise TypeError(msg.format(repr(names)))
for hook in sys.meta_path:
if isinstance(hook, rewrite.AssertionRewritingHook):
importhook = hook
break
else:
importhook = DummyRewriteHook()
importhook.mark_rewrite(*names)
class DummyRewriteHook(object):
"""A no-op import hook for when rewriting is disabled."""
def mark_rewrite(self, *names):
pass
class AssertionState(object):
"""State for the assertion plugin."""
def __init__(self, config, mode):
self.mode = mode
self.trace = config.trace.root.get("assertion")
self.hook = None
def install_importhook(config):
"""Try to install the rewrite hook, raise SystemError if it fails."""
# Jython has an AST bug that make the assertion rewriting hook malfunction.
if sys.platform.startswith("java"):
raise SystemError("rewrite not supported")
config._assertstate = AssertionState(config, "rewrite")
config._assertstate.hook = hook = rewrite.AssertionRewritingHook(config)
sys.meta_path.insert(0, hook)
config._assertstate.trace("installed rewrite import hook")
def undo():
hook = config._assertstate.hook
if hook is not None and hook in sys.meta_path:
sys.meta_path.remove(hook)
config.add_cleanup(undo)
return hook
def pytest_collection(session):
# this hook is only called when test modules are collected
# so for example not in the master process of pytest-xdist
# (which does not collect test modules)
assertstate = getattr(session.config, "_assertstate", None)
if assertstate:
if assertstate.hook is not None:
assertstate.hook.set_session(session)
def pytest_runtest_setup(item):
"""Setup the pytest_assertrepr_compare hook
The newinterpret and rewrite modules will use util._reprcompare if
it exists to use custom reporting via the
pytest_assertrepr_compare hook. This sets up this custom
comparison for the test.
"""
def callbinrepr(op, left, right):
"""Call the pytest_assertrepr_compare hook and prepare the result
This uses the first result from the hook and then ensures the
following:
* Overly verbose explanations are truncated unless configured otherwise
(eg. if running in verbose mode).
* Embedded newlines are escaped to help util.format_explanation()
later.
* If the rewrite mode is used embedded %-characters are replaced
to protect later % formatting.
The result can be formatted by util.format_explanation() for
pretty printing.
"""
hook_result = item.ihook.pytest_assertrepr_compare(
config=item.config, op=op, left=left, right=right
)
for new_expl in hook_result:
if new_expl:
new_expl = truncate.truncate_if_required(new_expl, item)
new_expl = [line.replace("\n", "\\n") for line in new_expl]
res = six.text_type("\n~").join(new_expl)
if item.config.getvalue("assertmode") == "rewrite":
res = res.replace("%", "%%")
return res
util._reprcompare = callbinrepr
def pytest_runtest_teardown(item):
util._reprcompare = None
def pytest_sessionfinish(session):
assertstate = getattr(session.config, "_assertstate", None)
if assertstate:
if assertstate.hook is not None:
assertstate.hook.set_session(None)
# Expose this plugin's implementation for the pytest_assertrepr_compare hook
pytest_assertrepr_compare = util.assertrepr_compare

954
src/_pytest/assertion/rewrite.py Normal file
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"""Rewrite assertion AST to produce nice error messages"""
from __future__ import absolute_import, division, print_function
import ast
import errno
import itertools
import imp
import marshal
import os
import re
import six
import struct
import sys
import types
import atomicwrites
import py
from _pytest.assertion import util
# pytest caches rewritten pycs in __pycache__.
if hasattr(imp, "get_tag"):
PYTEST_TAG = imp.get_tag() + "-PYTEST"
else:
if hasattr(sys, "pypy_version_info"):
impl = "pypy"
elif sys.platform == "java":
impl = "jython"
else:
impl = "cpython"
ver = sys.version_info
PYTEST_TAG = "%s-%s%s-PYTEST" % (impl, ver[0], ver[1])
del ver, impl
PYC_EXT = ".py" + (__debug__ and "c" or "o")
PYC_TAIL = "." + PYTEST_TAG + PYC_EXT
ASCII_IS_DEFAULT_ENCODING = sys.version_info[0] < 3
if sys.version_info >= (3, 5):
ast_Call = ast.Call
else:
def ast_Call(a, b, c):
return ast.Call(a, b, c, None, None)
class AssertionRewritingHook(object):
"""PEP302 Import hook which rewrites asserts."""
def __init__(self, config):
self.config = config
self.fnpats = config.getini("python_files")
self.session = None
self.modules = {}
self._rewritten_names = set()
self._register_with_pkg_resources()
self._must_rewrite = set()
def set_session(self, session):
self.session = session
def find_module(self, name, path=None):
state = self.config._assertstate
state.trace("find_module called for: %s" % name)
names = name.rsplit(".", 1)
lastname = names[-1]
pth = None
if path is not None:
# Starting with Python 3.3, path is a _NamespacePath(), which
# causes problems if not converted to list.
path = list(path)
if len(path) == 1:
pth = path[0]
if pth is None:
try:
fd, fn, desc = imp.find_module(lastname, path)
except ImportError:
return None
if fd is not None:
fd.close()
tp = desc[2]
if tp == imp.PY_COMPILED:
if hasattr(imp, "source_from_cache"):
try:
fn = imp.source_from_cache(fn)
except ValueError:
# Python 3 doesn't like orphaned but still-importable
# .pyc files.
fn = fn[:-1]
else:
fn = fn[:-1]
elif tp != imp.PY_SOURCE:
# Don't know what this is.
return None
else:
fn = os.path.join(pth, name.rpartition(".")[2] + ".py")
fn_pypath = py.path.local(fn)
if not self._should_rewrite(name, fn_pypath, state):
return None
self._rewritten_names.add(name)
# The requested module looks like a test file, so rewrite it. This is
# the most magical part of the process: load the source, rewrite the
# asserts, and load the rewritten source. We also cache the rewritten
# module code in a special pyc. We must be aware of the possibility of
# concurrent pytest processes rewriting and loading pycs. To avoid
# tricky race conditions, we maintain the following invariant: The
# cached pyc is always a complete, valid pyc. Operations on it must be
# atomic. POSIX's atomic rename comes in handy.
write = not sys.dont_write_bytecode
cache_dir = os.path.join(fn_pypath.dirname, "__pycache__")
if write:
try:
os.mkdir(cache_dir)
except OSError:
e = sys.exc_info()[1].errno
if e == errno.EEXIST:
# Either the __pycache__ directory already exists (the
# common case) or it's blocked by a non-dir node. In the
# latter case, we'll ignore it in _write_pyc.
pass
elif e in [errno.ENOENT, errno.ENOTDIR]:
# One of the path components was not a directory, likely
# because we're in a zip file.
write = False
elif e in [errno.EACCES, errno.EROFS, errno.EPERM]:
state.trace("read only directory: %r" % fn_pypath.dirname)
write = False
else:
raise
cache_name = fn_pypath.basename[:-3] + PYC_TAIL
pyc = os.path.join(cache_dir, cache_name)
# Notice that even if we're in a read-only directory, I'm going
# to check for a cached pyc. This may not be optimal...
co = _read_pyc(fn_pypath, pyc, state.trace)
if co is None:
state.trace("rewriting %r" % (fn,))
source_stat, co = _rewrite_test(self.config, fn_pypath)
if co is None:
# Probably a SyntaxError in the test.
return None
if write:
_write_pyc(state, co, source_stat, pyc)
else:
state.trace("found cached rewritten pyc for %r" % (fn,))
self.modules[name] = co, pyc
return self
def _should_rewrite(self, name, fn_pypath, state):
# always rewrite conftest files
fn = str(fn_pypath)
if fn_pypath.basename == "conftest.py":
state.trace("rewriting conftest file: %r" % (fn,))
return True
if self.session is not None:
if self.session.isinitpath(fn):
state.trace("matched test file (was specified on cmdline): %r" % (fn,))
return True
# modules not passed explicitly on the command line are only
# rewritten if they match the naming convention for test files
for pat in self.fnpats:
if fn_pypath.fnmatch(pat):
state.trace("matched test file %r" % (fn,))
return True
for marked in self._must_rewrite:
if name == marked or name.startswith(marked + "."):
state.trace("matched marked file %r (from %r)" % (name, marked))
return True
return False
def mark_rewrite(self, *names):
"""Mark import names as needing to be rewritten.
The named module or package as well as any nested modules will
be rewritten on import.
"""
already_imported = (
set(names).intersection(sys.modules).difference(self._rewritten_names)
)
for name in already_imported:
if not AssertionRewriter.is_rewrite_disabled(
sys.modules[name].__doc__ or ""
):
self._warn_already_imported(name)
self._must_rewrite.update(names)
def _warn_already_imported(self, name):
self.config.warn(
"P1", "Module already imported so cannot be rewritten: %s" % name
)
def load_module(self, name):
# If there is an existing module object named 'fullname' in
# sys.modules, the loader must use that existing module. (Otherwise,
# the reload() builtin will not work correctly.)
if name in sys.modules:
return sys.modules[name]
co, pyc = self.modules.pop(name)
# I wish I could just call imp.load_compiled here, but __file__ has to
# be set properly. In Python 3.2+, this all would be handled correctly
# by load_compiled.
mod = sys.modules[name] = imp.new_module(name)
try:
mod.__file__ = co.co_filename
# Normally, this attribute is 3.2+.
mod.__cached__ = pyc
mod.__loader__ = self
py.builtin.exec_(co, mod.__dict__)
except: # noqa
if name in sys.modules:
del sys.modules[name]
raise
return sys.modules[name]
def is_package(self, name):
try:
fd, fn, desc = imp.find_module(name)
except ImportError:
return False
if fd is not None:
fd.close()
tp = desc[2]
return tp == imp.PKG_DIRECTORY
@classmethod
def _register_with_pkg_resources(cls):
"""
Ensure package resources can be loaded from this loader. May be called
multiple times, as the operation is idempotent.
"""
try:
import pkg_resources
# access an attribute in case a deferred importer is present
pkg_resources.__name__
except ImportError:
return
# Since pytest tests are always located in the file system, the
# DefaultProvider is appropriate.
pkg_resources.register_loader_type(cls, pkg_resources.DefaultProvider)
def get_data(self, pathname):
"""Optional PEP302 get_data API.
"""
with open(pathname, "rb") as f:
return f.read()
def _write_pyc(state, co, source_stat, pyc):
# Technically, we don't have to have the same pyc format as
# (C)Python, since these "pycs" should never be seen by builtin
# import. However, there's little reason deviate, and I hope
# sometime to be able to use imp.load_compiled to load them. (See
# the comment in load_module above.)
try:
with atomicwrites.atomic_write(pyc, mode="wb", overwrite=True) as fp:
fp.write(imp.get_magic())
mtime = int(source_stat.mtime)
size = source_stat.size & 0xFFFFFFFF
fp.write(struct.pack("<ll", mtime, size))
fp.write(marshal.dumps(co))
except EnvironmentError as e:
state.trace("error writing pyc file at %s: errno=%s" % (pyc, e.errno))
# we ignore any failure to write the cache file
# there are many reasons, permission-denied, __pycache__ being a
# file etc.
return False
return True
RN = "\r\n".encode("utf-8")
N = "\n".encode("utf-8")
cookie_re = re.compile(r"^[ \t\f]*#.*coding[:=][ \t]*[-\w.]+")
BOM_UTF8 = "\xef\xbb\xbf"
def _rewrite_test(config, fn):
"""Try to read and rewrite *fn* and return the code object."""
state = config._assertstate
try:
stat = fn.stat()
source = fn.read("rb")
except EnvironmentError:
return None, None
if ASCII_IS_DEFAULT_ENCODING:
# ASCII is the default encoding in Python 2. Without a coding
# declaration, Python 2 will complain about any bytes in the file
# outside the ASCII range. Sadly, this behavior does not extend to
# compile() or ast.parse(), which prefer to interpret the bytes as
# latin-1. (At least they properly handle explicit coding cookies.) To
# preserve this error behavior, we could force ast.parse() to use ASCII
# as the encoding by inserting a coding cookie. Unfortunately, that
# messes up line numbers. Thus, we have to check ourselves if anything
# is outside the ASCII range in the case no encoding is explicitly
# declared. For more context, see issue #269. Yay for Python 3 which
# gets this right.
end1 = source.find("\n")
end2 = source.find("\n", end1 + 1)
if (
not source.startswith(BOM_UTF8)
and cookie_re.match(source[0:end1]) is None
and cookie_re.match(source[end1 + 1:end2]) is None
):
if hasattr(state, "_indecode"):
# encodings imported us again, so don't rewrite.
return None, None
state._indecode = True
try:
try:
source.decode("ascii")
except UnicodeDecodeError:
# Let it fail in real import.
return None, None
finally:
del state._indecode
try:
tree = ast.parse(source)
except SyntaxError:
# Let this pop up again in the real import.
state.trace("failed to parse: %r" % (fn,))
return None, None
rewrite_asserts(tree, fn, config)
try:
co = compile(tree, fn.strpath, "exec", dont_inherit=True)
except SyntaxError:
# It's possible that this error is from some bug in the
# assertion rewriting, but I don't know of a fast way to tell.
state.trace("failed to compile: %r" % (fn,))
return None, None
return stat, co
def _read_pyc(source, pyc, trace=lambda x: None):
"""Possibly read a pytest pyc containing rewritten code.
Return rewritten code if successful or None if not.
"""
try:
fp = open(pyc, "rb")
except IOError:
return None
with fp:
try:
mtime = int(source.mtime())
size = source.size()
data = fp.read(12)
except EnvironmentError as e:
trace("_read_pyc(%s): EnvironmentError %s" % (source, e))
return None
# Check for invalid or out of date pyc file.
if (
len(data) != 12
or data[:4] != imp.get_magic()
or struct.unpack("<ll", data[4:]) != (mtime, size)
):
trace("_read_pyc(%s): invalid or out of date pyc" % source)
return None
try:
co = marshal.load(fp)
except Exception as e:
trace("_read_pyc(%s): marshal.load error %s" % (source, e))
return None
if not isinstance(co, types.CodeType):
trace("_read_pyc(%s): not a code object" % source)
return None
return co
def rewrite_asserts(mod, module_path=None, config=None):
"""Rewrite the assert statements in mod."""
AssertionRewriter(module_path, config).run(mod)
def _saferepr(obj):
"""Get a safe repr of an object for assertion error messages.
The assertion formatting (util.format_explanation()) requires
newlines to be escaped since they are a special character for it.
Normally assertion.util.format_explanation() does this but for a
custom repr it is possible to contain one of the special escape
sequences, especially '\n{' and '\n}' are likely to be present in
JSON reprs.
"""
repr = py.io.saferepr(obj)
if isinstance(repr, six.text_type):
t = six.text_type
else:
t = six.binary_type
return repr.replace(t("\n"), t("\\n"))
from _pytest.assertion.util import format_explanation as _format_explanation # noqa
def _format_assertmsg(obj):
"""Format the custom assertion message given.
For strings this simply replaces newlines with '\n~' so that
util.format_explanation() will preserve them instead of escaping
newlines. For other objects py.io.saferepr() is used first.
"""
# reprlib appears to have a bug which means that if a string
# contains a newline it gets escaped, however if an object has a
# .__repr__() which contains newlines it does not get escaped.
# However in either case we want to preserve the newline.
if isinstance(obj, six.text_type) or isinstance(obj, six.binary_type):
s = obj
is_repr = False
else:
s = py.io.saferepr(obj)
is_repr = True
if isinstance(s, six.text_type):
t = six.text_type
else:
t = six.binary_type
s = s.replace(t("\n"), t("\n~")).replace(t("%"), t("%%"))
if is_repr:
s = s.replace(t("\\n"), t("\n~"))
return s
def _should_repr_global_name(obj):
return not hasattr(obj, "__name__") and not callable(obj)
def _format_boolop(explanations, is_or):
explanation = "(" + (is_or and " or " or " and ").join(explanations) + ")"
if isinstance(explanation, six.text_type):
t = six.text_type
else:
t = six.binary_type
return explanation.replace(t("%"), t("%%"))
def _call_reprcompare(ops, results, expls, each_obj):
for i, res, expl in zip(range(len(ops)), results, expls):
try:
done = not res
except Exception:
done = True
if done:
break
if util._reprcompare is not None:
custom = util._reprcompare(ops[i], each_obj[i], each_obj[i + 1])
if custom is not None:
return custom
return expl
unary_map = {ast.Not: "not %s", ast.Invert: "~%s", ast.USub: "-%s", ast.UAdd: "+%s"}
binop_map = {
ast.BitOr: "|",
ast.BitXor: "^",
ast.BitAnd: "&",
ast.LShift: "<<",
ast.RShift: ">>",
ast.Add: "+",
ast.Sub: "-",
ast.Mult: "*",
ast.Div: "/",
ast.FloorDiv: "//",
ast.Mod: "%%", # escaped for string formatting
ast.Eq: "==",
ast.NotEq: "!=",
ast.Lt: "<",
ast.LtE: "<=",
ast.Gt: ">",
ast.GtE: ">=",
ast.Pow: "**",
ast.Is: "is",
ast.IsNot: "is not",
ast.In: "in",
ast.NotIn: "not in",
}
# Python 3.5+ compatibility
try:
binop_map[ast.MatMult] = "@"
except AttributeError:
pass
# Python 3.4+ compatibility
if hasattr(ast, "NameConstant"):
_NameConstant = ast.NameConstant
else:
def _NameConstant(c):
return ast.Name(str(c), ast.Load())
def set_location(node, lineno, col_offset):
"""Set node location information recursively."""
def _fix(node, lineno, col_offset):
if "lineno" in node._attributes:
node.lineno = lineno
if "col_offset" in node._attributes:
node.col_offset = col_offset
for child in ast.iter_child_nodes(node):
_fix(child, lineno, col_offset)
_fix(node, lineno, col_offset)
return node
class AssertionRewriter(ast.NodeVisitor):
"""Assertion rewriting implementation.
The main entrypoint is to call .run() with an ast.Module instance,
this will then find all the assert statements and rewrite them to
provide intermediate values and a detailed assertion error. See
http://pybites.blogspot.be/2011/07/behind-scenes-of-pytests-new-assertion.html
for an overview of how this works.
The entry point here is .run() which will iterate over all the
statements in an ast.Module and for each ast.Assert statement it
finds call .visit() with it. Then .visit_Assert() takes over and
is responsible for creating new ast statements to replace the
original assert statement: it rewrites the test of an assertion
to provide intermediate values and replace it with an if statement
which raises an assertion error with a detailed explanation in
case the expression is false.
For this .visit_Assert() uses the visitor pattern to visit all the
AST nodes of the ast.Assert.test field, each visit call returning
an AST node and the corresponding explanation string. During this
state is kept in several instance attributes:
:statements: All the AST statements which will replace the assert
statement.
:variables: This is populated by .variable() with each variable
used by the statements so that they can all be set to None at
the end of the statements.
:variable_counter: Counter to create new unique variables needed
by statements. Variables are created using .variable() and
have the form of "@py_assert0".
:on_failure: The AST statements which will be executed if the
assertion test fails. This is the code which will construct
the failure message and raises the AssertionError.
:explanation_specifiers: A dict filled by .explanation_param()
with %-formatting placeholders and their corresponding
expressions to use in the building of an assertion message.
This is used by .pop_format_context() to build a message.
:stack: A stack of the explanation_specifiers dicts maintained by
.push_format_context() and .pop_format_context() which allows
to build another %-formatted string while already building one.
This state is reset on every new assert statement visited and used
by the other visitors.
"""
def __init__(self, module_path, config):
super(AssertionRewriter, self).__init__()
self.module_path = module_path
self.config = config
def run(self, mod):
"""Find all assert statements in *mod* and rewrite them."""
if not mod.body:
# Nothing to do.
return
# Insert some special imports at the top of the module but after any
# docstrings and __future__ imports.
aliases = [
ast.alias(py.builtin.builtins.__name__, "@py_builtins"),
ast.alias("_pytest.assertion.rewrite", "@pytest_ar"),
]
doc = getattr(mod, "docstring", None)
expect_docstring = doc is None
if doc is not None and self.is_rewrite_disabled(doc):
return
pos = 0
lineno = 1
for item in mod.body:
if (
expect_docstring
and isinstance(item, ast.Expr)
and isinstance(item.value, ast.Str)
):
doc = item.value.s
if self.is_rewrite_disabled(doc):
return
expect_docstring = False
elif (
not isinstance(item, ast.ImportFrom)
or item.level > 0
or item.module != "__future__"
):
lineno = item.lineno
break
pos += 1
else:
lineno = item.lineno
imports = [
ast.Import([alias], lineno=lineno, col_offset=0) for alias in aliases
]
mod.body[pos:pos] = imports
# Collect asserts.
nodes = [mod]
while nodes:
node = nodes.pop()
for name, field in ast.iter_fields(node):
if isinstance(field, list):
new = []
for i, child in enumerate(field):
if isinstance(child, ast.Assert):
# Transform assert.
new.extend(self.visit(child))
else:
new.append(child)
if isinstance(child, ast.AST):
nodes.append(child)
setattr(node, name, new)
elif (
isinstance(field, ast.AST)
and
# Don't recurse into expressions as they can't contain
# asserts.
not isinstance(field, ast.expr)
):
nodes.append(field)
@staticmethod
def is_rewrite_disabled(docstring):
return "PYTEST_DONT_REWRITE" in docstring
def variable(self):
"""Get a new variable."""
# Use a character invalid in python identifiers to avoid clashing.
name = "@py_assert" + str(next(self.variable_counter))
self.variables.append(name)
return name
def assign(self, expr):
"""Give *expr* a name."""
name = self.variable()
self.statements.append(ast.Assign([ast.Name(name, ast.Store())], expr))
return ast.Name(name, ast.Load())
def display(self, expr):
"""Call py.io.saferepr on the expression."""
return self.helper("saferepr", expr)
def helper(self, name, *args):
"""Call a helper in this module."""
py_name = ast.Name("@pytest_ar", ast.Load())
attr = ast.Attribute(py_name, "_" + name, ast.Load())
return ast_Call(attr, list(args), [])
def builtin(self, name):
"""Return the builtin called *name*."""
builtin_name = ast.Name("@py_builtins", ast.Load())
return ast.Attribute(builtin_name, name, ast.Load())
def explanation_param(self, expr):
"""Return a new named %-formatting placeholder for expr.
This creates a %-formatting placeholder for expr in the
current formatting context, e.g. ``%(py0)s``. The placeholder
and expr are placed in the current format context so that it
can be used on the next call to .pop_format_context().
"""
specifier = "py" + str(next(self.variable_counter))
self.explanation_specifiers[specifier] = expr
return "%(" + specifier + ")s"
def push_format_context(self):
"""Create a new formatting context.
The format context is used for when an explanation wants to
have a variable value formatted in the assertion message. In
this case the value required can be added using
.explanation_param(). Finally .pop_format_context() is used
to format a string of %-formatted values as added by
.explanation_param().
"""
self.explanation_specifiers = {}
self.stack.append(self.explanation_specifiers)
def pop_format_context(self, expl_expr):
"""Format the %-formatted string with current format context.
The expl_expr should be an ast.Str instance constructed from
the %-placeholders created by .explanation_param(). This will
add the required code to format said string to .on_failure and
return the ast.Name instance of the formatted string.
"""
current = self.stack.pop()
if self.stack:
self.explanation_specifiers = self.stack[-1]
keys = [ast.Str(key) for key in current.keys()]
format_dict = ast.Dict(keys, list(current.values()))
form = ast.BinOp(expl_expr, ast.Mod(), format_dict)
name = "@py_format" + str(next(self.variable_counter))
self.on_failure.append(ast.Assign([ast.Name(name, ast.Store())], form))
return ast.Name(name, ast.Load())
def generic_visit(self, node):
"""Handle expressions we don't have custom code for."""
assert isinstance(node, ast.expr)
res = self.assign(node)
return res, self.explanation_param(self.display(res))
def visit_Assert(self, assert_):
"""Return the AST statements to replace the ast.Assert instance.
This rewrites the test of an assertion to provide
intermediate values and replace it with an if statement which
raises an assertion error with a detailed explanation in case
the expression is false.
"""
if isinstance(assert_.test, ast.Tuple) and self.config is not None:
fslocation = (self.module_path, assert_.lineno)
self.config.warn(
"R1",
"assertion is always true, perhaps " "remove parentheses?",
fslocation=fslocation,
)
self.statements = []
self.variables = []
self.variable_counter = itertools.count()
self.stack = []
self.on_failure = []
self.push_format_context()
# Rewrite assert into a bunch of statements.
top_condition, explanation = self.visit(assert_.test)
# Create failure message.
body = self.on_failure
negation = ast.UnaryOp(ast.Not(), top_condition)
self.statements.append(ast.If(negation, body, []))
if assert_.msg:
assertmsg = self.helper("format_assertmsg", assert_.msg)
explanation = "\n>assert " + explanation
else:
assertmsg = ast.Str("")
explanation = "assert " + explanation
template = ast.BinOp(assertmsg, ast.Add(), ast.Str(explanation))
msg = self.pop_format_context(template)
fmt = self.helper("format_explanation", msg)
err_name = ast.Name("AssertionError", ast.Load())
exc = ast_Call(err_name, [fmt], [])
if sys.version_info[0] >= 3:
raise_ = ast.Raise(exc, None)
else:
raise_ = ast.Raise(exc, None, None)
body.append(raise_)
# Clear temporary variables by setting them to None.
if self.variables:
variables = [ast.Name(name, ast.Store()) for name in self.variables]
clear = ast.Assign(variables, _NameConstant(None))
self.statements.append(clear)
# Fix line numbers.
for stmt in self.statements:
set_location(stmt, assert_.lineno, assert_.col_offset)
return self.statements
def visit_Name(self, name):
# Display the repr of the name if it's a local variable or
# _should_repr_global_name() thinks it's acceptable.
locs = ast_Call(self.builtin("locals"), [], [])
inlocs = ast.Compare(ast.Str(name.id), [ast.In()], [locs])
dorepr = self.helper("should_repr_global_name", name)
test = ast.BoolOp(ast.Or(), [inlocs, dorepr])
expr = ast.IfExp(test, self.display(name), ast.Str(name.id))
return name, self.explanation_param(expr)
def visit_BoolOp(self, boolop):
res_var = self.variable()
expl_list = self.assign(ast.List([], ast.Load()))
app = ast.Attribute(expl_list, "append", ast.Load())
is_or = int(isinstance(boolop.op, ast.Or))
body = save = self.statements
fail_save = self.on_failure
levels = len(boolop.values) - 1
self.push_format_context()
# Process each operand, short-circuting if needed.
for i, v in enumerate(boolop.values):
if i:
fail_inner = []
# cond is set in a prior loop iteration below
self.on_failure.append(ast.If(cond, fail_inner, [])) # noqa
self.on_failure = fail_inner
self.push_format_context()
res, expl = self.visit(v)
body.append(ast.Assign([ast.Name(res_var, ast.Store())], res))
expl_format = self.pop_format_context(ast.Str(expl))
call = ast_Call(app, [expl_format], [])
self.on_failure.append(ast.Expr(call))
if i < levels:
cond = res
if is_or:
cond = ast.UnaryOp(ast.Not(), cond)
inner = []
self.statements.append(ast.If(cond, inner, []))
self.statements = body = inner
self.statements = save
self.on_failure = fail_save
expl_template = self.helper("format_boolop", expl_list, ast.Num(is_or))
expl = self.pop_format_context(expl_template)
return ast.Name(res_var, ast.Load()), self.explanation_param(expl)
def visit_UnaryOp(self, unary):
pattern = unary_map[unary.op.__class__]
operand_res, operand_expl = self.visit(unary.operand)
res = self.assign(ast.UnaryOp(unary.op, operand_res))
return res, pattern % (operand_expl,)
def visit_BinOp(self, binop):
symbol = binop_map[binop.op.__class__]
left_expr, left_expl = self.visit(binop.left)
right_expr, right_expl = self.visit(binop.right)
explanation = "(%s %s %s)" % (left_expl, symbol, right_expl)
res = self.assign(ast.BinOp(left_expr, binop.op, right_expr))
return res, explanation
def visit_Call_35(self, call):
"""
visit `ast.Call` nodes on Python3.5 and after
"""
new_func, func_expl = self.visit(call.func)
arg_expls = []
new_args = []
new_kwargs = []
for arg in call.args:
res, expl = self.visit(arg)
arg_expls.append(expl)
new_args.append(res)
for keyword in call.keywords:
res, expl = self.visit(keyword.value)
new_kwargs.append(ast.keyword(keyword.arg, res))
if keyword.arg:
arg_expls.append(keyword.arg + "=" + expl)
else: # **args have `arg` keywords with an .arg of None
arg_expls.append("**" + expl)
expl = "%s(%s)" % (func_expl, ", ".join(arg_expls))
new_call = ast.Call(new_func, new_args, new_kwargs)
res = self.assign(new_call)
res_expl = self.explanation_param(self.display(res))
outer_expl = "%s\n{%s = %s\n}" % (res_expl, res_expl, expl)
return res, outer_expl
def visit_Starred(self, starred):
# From Python 3.5, a Starred node can appear in a function call
res, expl = self.visit(starred.value)
return starred, "*" + expl
def visit_Call_legacy(self, call):
"""
visit `ast.Call nodes on 3.4 and below`
"""
new_func, func_expl = self.visit(call.func)
arg_expls = []
new_args = []
new_kwargs = []
new_star = new_kwarg = None
for arg in call.args:
res, expl = self.visit(arg)
new_args.append(res)
arg_expls.append(expl)
for keyword in call.keywords:
res, expl = self.visit(keyword.value)
new_kwargs.append(ast.keyword(keyword.arg, res))
arg_expls.append(keyword.arg + "=" + expl)
if call.starargs:
new_star, expl = self.visit(call.starargs)
arg_expls.append("*" + expl)
if call.kwargs:
new_kwarg, expl = self.visit(call.kwargs)
arg_expls.append("**" + expl)
expl = "%s(%s)" % (func_expl, ", ".join(arg_expls))
new_call = ast.Call(new_func, new_args, new_kwargs, new_star, new_kwarg)
res = self.assign(new_call)
res_expl = self.explanation_param(self.display(res))
outer_expl = "%s\n{%s = %s\n}" % (res_expl, res_expl, expl)
return res, outer_expl
# ast.Call signature changed on 3.5,
# conditionally change which methods is named
# visit_Call depending on Python version
if sys.version_info >= (3, 5):
visit_Call = visit_Call_35
else:
visit_Call = visit_Call_legacy
def visit_Attribute(self, attr):
if not isinstance(attr.ctx, ast.Load):
return self.generic_visit(attr)
value, value_expl = self.visit(attr.value)
res = self.assign(ast.Attribute(value, attr.attr, ast.Load()))
res_expl = self.explanation_param(self.display(res))
pat = "%s\n{%s = %s.%s\n}"
expl = pat % (res_expl, res_expl, value_expl, attr.attr)
return res, expl
def visit_Compare(self, comp):
self.push_format_context()
left_res, left_expl = self.visit(comp.left)
if isinstance(comp.left, (ast.Compare, ast.BoolOp)):
left_expl = "({})".format(left_expl)
res_variables = [self.variable() for i in range(len(comp.ops))]
load_names = [ast.Name(v, ast.Load()) for v in res_variables]
store_names = [ast.Name(v, ast.Store()) for v in res_variables]
it = zip(range(len(comp.ops)), comp.ops, comp.comparators)
expls = []
syms = []
results = [left_res]
for i, op, next_operand in it:
next_res, next_expl = self.visit(next_operand)
if isinstance(next_operand, (ast.Compare, ast.BoolOp)):
next_expl = "({})".format(next_expl)
results.append(next_res)
sym = binop_map[op.__class__]
syms.append(ast.Str(sym))
expl = "%s %s %s" % (left_expl, sym, next_expl)
expls.append(ast.Str(expl))
res_expr = ast.Compare(left_res, [op], [next_res])
self.statements.append(ast.Assign([store_names[i]], res_expr))
left_res, left_expl = next_res, next_expl
# Use pytest.assertion.util._reprcompare if that's available.
expl_call = self.helper(
"call_reprcompare",
ast.Tuple(syms, ast.Load()),
ast.Tuple(load_names, ast.Load()),
ast.Tuple(expls, ast.Load()),
ast.Tuple(results, ast.Load()),
)
if len(comp.ops) > 1:
res = ast.BoolOp(ast.And(), load_names)
else:
res = load_names[0]
return res, self.explanation_param(self.pop_format_context(expl_call))

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"""
Utilities for truncating assertion output.
Current default behaviour is to truncate assertion explanations at
~8 terminal lines, unless running in "-vv" mode or running on CI.
"""
from __future__ import absolute_import, division, print_function
import os
import six
DEFAULT_MAX_LINES = 8
DEFAULT_MAX_CHARS = 8 * 80
USAGE_MSG = "use '-vv' to show"
def truncate_if_required(explanation, item, max_length=None):
"""
Truncate this assertion explanation if the given test item is eligible.
"""
if _should_truncate_item(item):
return _truncate_explanation(explanation)
return explanation
def _should_truncate_item(item):
"""
Whether or not this test item is eligible for truncation.
"""
verbose = item.config.option.verbose
return verbose < 2 and not _running_on_ci()
def _running_on_ci():
"""Check if we're currently running on a CI system."""
env_vars = ["CI", "BUILD_NUMBER"]
return any(var in os.environ for var in env_vars)
def _truncate_explanation(input_lines, max_lines=None, max_chars=None):
"""
Truncate given list of strings that makes up the assertion explanation.
Truncates to either 8 lines, or 640 characters - whichever the input reaches
first. The remaining lines will be replaced by a usage message.
"""
if max_lines is None:
max_lines = DEFAULT_MAX_LINES
if max_chars is None:
max_chars = DEFAULT_MAX_CHARS
# Check if truncation required
input_char_count = len("".join(input_lines))
if len(input_lines) <= max_lines and input_char_count <= max_chars:
return input_lines
# Truncate first to max_lines, and then truncate to max_chars if max_chars
# is exceeded.
truncated_explanation = input_lines[:max_lines]
truncated_explanation = _truncate_by_char_count(truncated_explanation, max_chars)
# Add ellipsis to final line
truncated_explanation[-1] = truncated_explanation[-1] + "..."
# Append useful message to explanation
truncated_line_count = len(input_lines) - len(truncated_explanation)
truncated_line_count += 1 # Account for the part-truncated final line
msg = "...Full output truncated"
if truncated_line_count == 1:
msg += " ({} line hidden)".format(truncated_line_count)
else:
msg += " ({} lines hidden)".format(truncated_line_count)
msg += ", {}".format(USAGE_MSG)
truncated_explanation.extend([six.text_type(""), six.text_type(msg)])
return truncated_explanation
def _truncate_by_char_count(input_lines, max_chars):
# Check if truncation required
if len("".join(input_lines)) <= max_chars:
return input_lines
# Find point at which input length exceeds total allowed length
iterated_char_count = 0
for iterated_index, input_line in enumerate(input_lines):
if iterated_char_count + len(input_line) > max_chars:
break
iterated_char_count += len(input_line)
# Create truncated explanation with modified final line
truncated_result = input_lines[:iterated_index]
final_line = input_lines[iterated_index]
if final_line:
final_line_truncate_point = max_chars - iterated_char_count
final_line = final_line[:final_line_truncate_point]
truncated_result.append(final_line)
return truncated_result

338
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"""Utilities for assertion debugging"""
from __future__ import absolute_import, division, print_function
import pprint
import _pytest._code
import py
import six
from ..compat import Sequence
u = six.text_type
# The _reprcompare attribute on the util module is used by the new assertion
# interpretation code and assertion rewriter to detect this plugin was
# loaded and in turn call the hooks defined here as part of the
# DebugInterpreter.
_reprcompare = None
# the re-encoding is needed for python2 repr
# with non-ascii characters (see issue 877 and 1379)
def ecu(s):
try:
return u(s, "utf-8", "replace")
except TypeError:
return s
def format_explanation(explanation):
"""This formats an explanation
Normally all embedded newlines are escaped, however there are
three exceptions: \n{, \n} and \n~. The first two are intended
cover nested explanations, see function and attribute explanations
for examples (.visit_Call(), visit_Attribute()). The last one is
for when one explanation needs to span multiple lines, e.g. when
displaying diffs.
"""
explanation = ecu(explanation)
lines = _split_explanation(explanation)
result = _format_lines(lines)
return u("\n").join(result)
def _split_explanation(explanation):
"""Return a list of individual lines in the explanation
This will return a list of lines split on '\n{', '\n}' and '\n~'.
Any other newlines will be escaped and appear in the line as the
literal '\n' characters.
"""
raw_lines = (explanation or u("")).split("\n")
lines = [raw_lines[0]]
for values in raw_lines[1:]:
if values and values[0] in ["{", "}", "~", ">"]:
lines.append(values)
else:
lines[-1] += "\\n" + values
return lines
def _format_lines(lines):
"""Format the individual lines
This will replace the '{', '}' and '~' characters of our mini
formatting language with the proper 'where ...', 'and ...' and ' +
...' text, taking care of indentation along the way.
Return a list of formatted lines.
"""
result = lines[:1]
stack = [0]
stackcnt = [0]
for line in lines[1:]:
if line.startswith("{"):
if stackcnt[-1]:
s = u("and ")
else:
s = u("where ")
stack.append(len(result))
stackcnt[-1] += 1
stackcnt.append(0)
result.append(u(" +") + u(" ") * (len(stack) - 1) + s + line[1:])
elif line.startswith("}"):
stack.pop()
stackcnt.pop()
result[stack[-1]] += line[1:]
else:
assert line[0] in ["~", ">"]
stack[-1] += 1
indent = len(stack) if line.startswith("~") else len(stack) - 1
result.append(u(" ") * indent + line[1:])
assert len(stack) == 1
return result
# Provide basestring in python3
try:
basestring = basestring
except NameError:
basestring = str
def assertrepr_compare(config, op, left, right):
"""Return specialised explanations for some operators/operands"""
width = 80 - 15 - len(op) - 2 # 15 chars indentation, 1 space around op
left_repr = py.io.saferepr(left, maxsize=int(width // 2))
right_repr = py.io.saferepr(right, maxsize=width - len(left_repr))
summary = u("%s %s %s") % (ecu(left_repr), op, ecu(right_repr))
def issequence(x):
return isinstance(x, Sequence) and not isinstance(x, basestring)
def istext(x):
return isinstance(x, basestring)
def isdict(x):
return isinstance(x, dict)
def isset(x):
return isinstance(x, (set, frozenset))
def isiterable(obj):
try:
iter(obj)
return not istext(obj)
except TypeError:
return False
verbose = config.getoption("verbose")
explanation = None
try:
if op == "==":
if istext(left) and istext(right):
explanation = _diff_text(left, right, verbose)
else:
if issequence(left) and issequence(right):
explanation = _compare_eq_sequence(left, right, verbose)
elif isset(left) and isset(right):
explanation = _compare_eq_set(left, right, verbose)
elif isdict(left) and isdict(right):
explanation = _compare_eq_dict(left, right, verbose)
if isiterable(left) and isiterable(right):
expl = _compare_eq_iterable(left, right, verbose)
if explanation is not None:
explanation.extend(expl)
else:
explanation = expl
elif op == "not in":
if istext(left) and istext(right):
explanation = _notin_text(left, right, verbose)
except Exception:
explanation = [
u(
"(pytest_assertion plugin: representation of details failed. "
"Probably an object has a faulty __repr__.)"
),
u(_pytest._code.ExceptionInfo()),
]
if not explanation:
return None
return [summary] + explanation
def _diff_text(left, right, verbose=False):
"""Return the explanation for the diff between text or bytes
Unless --verbose is used this will skip leading and trailing
characters which are identical to keep the diff minimal.
If the input are bytes they will be safely converted to text.
"""
from difflib import ndiff
explanation = []
def escape_for_readable_diff(binary_text):
"""
Ensures that the internal string is always valid unicode, converting any bytes safely to valid unicode.
This is done using repr() which then needs post-processing to fix the encompassing quotes and un-escape
newlines and carriage returns (#429).
"""
r = six.text_type(repr(binary_text)[1:-1])
r = r.replace(r"\n", "\n")
r = r.replace(r"\r", "\r")
return r
if isinstance(left, six.binary_type):
left = escape_for_readable_diff(left)
if isinstance(right, six.binary_type):
right = escape_for_readable_diff(right)
if not verbose:
i = 0 # just in case left or right has zero length
for i in range(min(len(left), len(right))):
if left[i] != right[i]:
break
if i > 42:
i -= 10 # Provide some context
explanation = [
u("Skipping %s identical leading " "characters in diff, use -v to show")
% i
]
left = left[i:]
right = right[i:]
if len(left) == len(right):
for i in range(len(left)):
if left[-i] != right[-i]:
break
if i > 42:
i -= 10 # Provide some context
explanation += [
u(
"Skipping %s identical trailing "
"characters in diff, use -v to show"
)
% i
]
left = left[:-i]
right = right[:-i]
keepends = True
if left.isspace() or right.isspace():
left = repr(str(left))
right = repr(str(right))
explanation += [u"Strings contain only whitespace, escaping them using repr()"]
explanation += [
line.strip("\n")
for line in ndiff(left.splitlines(keepends), right.splitlines(keepends))
]
return explanation
def _compare_eq_iterable(left, right, verbose=False):
if not verbose:
return [u("Use -v to get the full diff")]
# dynamic import to speedup pytest
import difflib
try:
left_formatting = pprint.pformat(left).splitlines()
right_formatting = pprint.pformat(right).splitlines()
explanation = [u("Full diff:")]
except Exception:
# hack: PrettyPrinter.pformat() in python 2 fails when formatting items that can't be sorted(), ie, calling
# sorted() on a list would raise. See issue #718.
# As a workaround, the full diff is generated by using the repr() string of each item of each container.
left_formatting = sorted(repr(x) for x in left)
right_formatting = sorted(repr(x) for x in right)
explanation = [u("Full diff (fallback to calling repr on each item):")]
explanation.extend(
line.strip() for line in difflib.ndiff(left_formatting, right_formatting)
)
return explanation
def _compare_eq_sequence(left, right, verbose=False):
explanation = []
for i in range(min(len(left), len(right))):
if left[i] != right[i]:
explanation += [u("At index %s diff: %r != %r") % (i, left[i], right[i])]
break
if len(left) > len(right):
explanation += [
u("Left contains more items, first extra item: %s")
% py.io.saferepr(left[len(right)])
]
elif len(left) < len(right):
explanation += [
u("Right contains more items, first extra item: %s")
% py.io.saferepr(right[len(left)])
]
return explanation
def _compare_eq_set(left, right, verbose=False):
explanation = []
diff_left = left - right
diff_right = right - left
if diff_left:
explanation.append(u("Extra items in the left set:"))
for item in diff_left:
explanation.append(py.io.saferepr(item))
if diff_right:
explanation.append(u("Extra items in the right set:"))
for item in diff_right:
explanation.append(py.io.saferepr(item))
return explanation
def _compare_eq_dict(left, right, verbose=False):
explanation = []
common = set(left).intersection(set(right))
same = {k: left[k] for k in common if left[k] == right[k]}
if same and verbose < 2:
explanation += [u("Omitting %s identical items, use -vv to show") % len(same)]
elif same:
explanation += [u("Common items:")]
explanation += pprint.pformat(same).splitlines()
diff = {k for k in common if left[k] != right[k]}
if diff:
explanation += [u("Differing items:")]
for k in diff:
explanation += [
py.io.saferepr({k: left[k]}) + " != " + py.io.saferepr({k: right[k]})
]
extra_left = set(left) - set(right)
if extra_left:
explanation.append(u("Left contains more items:"))
explanation.extend(
pprint.pformat({k: left[k] for k in extra_left}).splitlines()
)
extra_right = set(right) - set(left)
if extra_right:
explanation.append(u("Right contains more items:"))
explanation.extend(
pprint.pformat({k: right[k] for k in extra_right}).splitlines()
)
return explanation
def _notin_text(term, text, verbose=False):
index = text.find(term)
head = text[:index]
tail = text[index + len(term):]
correct_text = head + tail
diff = _diff_text(correct_text, text, verbose)
newdiff = [u("%s is contained here:") % py.io.saferepr(term, maxsize=42)]
for line in diff:
if line.startswith(u("Skipping")):
continue
if line.startswith(u("- ")):
continue
if line.startswith(u("+ ")):
newdiff.append(u(" ") + line[2:])
else:
newdiff.append(line)
return newdiff