copy saferepr from pylib verbatim

Copied from b9da2ed6178cd37d4ed6b41f9fa8234dce96973f

src/_pytest/_io/saferepr.py

@@ -0,0 +1,71 @@
+import py
+import sys
+
+builtin_repr = repr
+
+reprlib = py.builtin._tryimport('repr', 'reprlib')
+
+class SafeRepr(reprlib.Repr):
+    """ subclass of repr.Repr that limits the resulting size of repr()
+        and includes information on exceptions raised during the call.
+    """
+    def repr(self, x):
+        return self._callhelper(reprlib.Repr.repr, self, x)
+
+    def repr_unicode(self, x, level):
+        # Strictly speaking wrong on narrow builds
+        def repr(u):
+            if "'" not in u:
+                return py.builtin._totext("'%s'") % u
+            elif '"' not in u:
+                return py.builtin._totext('"%s"') % u
+            else:
+                return py.builtin._totext("'%s'") % u.replace("'", r"\'")
+        s = repr(x[:self.maxstring])
+        if len(s) > self.maxstring:
+            i = max(0, (self.maxstring-3)//2)
+            j = max(0, self.maxstring-3-i)
+            s = repr(x[:i] + x[len(x)-j:])
+            s = s[:i] + '...' + s[len(s)-j:]
+        return s
+
+    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 py.builtin._sysex:
+            raise
+        except:
+            cls, e, tb = sys.exc_info()
+            exc_name = getattr(cls, '__name__', 'unknown')
+            try:
+                exc_info = str(e)
+            except py.builtin._sysex:
+                raise
+            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.maxsize:
+                i = max(0, (self.maxsize-3)//2)
+                j = max(0, self.maxsize-3-i)
+                s = s[:i] + '...' + s[len(s)-j:]
+            return s
+
+def saferepr(obj, maxsize=240):
+    """ return a size-limited safe repr-string for the given object.
+    Failing __repr__ functions of user instances will be represented
+    with a short exception info and 'saferepr' generally takes
+    care to never raise exceptions itself.  This function is a wrapper
+    around the Repr/reprlib functionality of the standard 2.6 lib.
+    """
+    # review exception handling
+    srepr = SafeRepr()
+    srepr.maxstring = maxsize
+    srepr.maxsize = maxsize
+    srepr.maxother = 160
+    return srepr.repr(obj)

testing/io/test_saferepr.py

@@ -0,0 +1,75 @@
+# -*- coding: utf-8 -*-
+
+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
+        assert 'TypeError' in saferepr(BrokenRepr("string"))
+
+        s2 = saferepr(BrokenRepr(BrokenReprException('omg even worse')))
+        assert 'NameError' not in s2
+        assert 'unknown' in s2
+
+    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_unicode(self):
+        val = py.builtin._totext('£€', 'utf-8')
+        reprval = py.builtin._totext("'£€'", 'utf-8')
+        assert saferepr(val) == reprval
+
+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)
+