introduce new py.io.saferepr for printing the 'repr' of an object safely

and without consuming too much space

--HG--
branch : trunk

testing/io_/test_saferepr.py

@@ -0,0 +1,99 @@
+from __future__ import generators
+import py
+import sys
+
+saferepr = py.io.saferepr
+
+class TestSafeRepr:
+    def test_simple_repr(self):
+        assert saferepr(1) == '1'
+        assert saferepr(None) == 'None'
+
+    def test_maxsize(self):
+        s = saferepr('x'*50, maxsize=25)
+        assert len(s) == 25
+        expected = repr('x'*10 + '...' + 'x'*10)
+        assert s == expected
+
+    def test_maxsize_error_on_instance(self):
+        class A:
+            def __repr__(self):
+                raise ValueError('...')
+
+        s = saferepr(('*'*50, A()), maxsize=25)
+        assert len(s) == 25
+        assert s[0] == '(' and s[-1] == ')'
+    
+    def test_exceptions(self):
+        class BrokenRepr:
+            def __init__(self, ex):
+                self.ex = ex
+                foo = 0
+            def __repr__(self):
+                raise self.ex
+        class BrokenReprException(Exception):
+            __str__ = None 
+            __repr__ = None
+        assert 'Exception' in saferepr(BrokenRepr(Exception("broken")))
+        s = saferepr(BrokenReprException("really broken"))
+        assert 'TypeError' in s
+        if py.std.sys.version_info < (2,6):
+            assert 'unknown' in saferepr(BrokenRepr("string"))
+        else:
+            assert 'TypeError' in saferepr(BrokenRepr("string"))
+
+    def test_big_repr(self):
+        from py._io.saferepr import SafeRepr
+        assert len(saferepr(range(1000))) <= \
+               len('[' + SafeRepr().maxlist * "1000" + ']')
+
+    def test_repr_on_newstyle(self):
+        class Function(object):
+            def __repr__(self):
+                return "<%s>" %(self.name)
+        try:
+            s = saferepr(Function())
+        except Exception:
+            py.test.fail("saferepr failed for newstyle class")
+  
+def test_builtin_patch_unpatch(monkeypatch):
+    cpy_builtin = py.builtin.builtins
+    comp = cpy_builtin.compile 
+    def mycompile(*args, **kwargs):
+        return comp(*args, **kwargs)
+    class Sub(AssertionError):
+        pass
+    monkeypatch.setattr(cpy_builtin, 'AssertionError', Sub)
+    monkeypatch.setattr(cpy_builtin, 'compile', mycompile)
+    py.code.patch_builtins()
+    assert cpy_builtin.AssertionError != Sub
+    assert cpy_builtin.compile != mycompile
+    py.code.unpatch_builtins()
+    assert cpy_builtin.AssertionError is Sub 
+    assert cpy_builtin.compile == mycompile 
+
+
+def test_unicode_handling():
+    value = py.builtin._totext('\xc4\x85\xc4\x87\n', 'utf-8').encode('utf8')
+    def f():
+        raise Exception(value)
+    excinfo = py.test.raises(Exception, f)
+    s = str(excinfo)
+    if sys.version_info[0] < 3:
+        u = unicode(excinfo)
+
+def test_unicode_or_repr():
+    from py._code.code import unicode_or_repr 
+    assert unicode_or_repr('hello') == "hello"
+    if sys.version_info[0] < 3:
+        s = unicode_or_repr('\xf6\xc4\x85')
+    else:
+        s = eval("unicode_or_repr(b'\\f6\\xc4\\x85')")
+    assert 'print-error' in s
+    assert 'c4' in s
+    class A:
+        def __repr__(self):
+            raise ValueError()
+    s = unicode_or_repr(A())
+    assert 'print-error' in s
+    assert 'ValueError' in s