Doctest 2 to 3

CHANGES.rst

@@ -10,6 +10,13 @@ Changes
 
 - Cleaned up useless 2to3 conversion.
 
+- Introduce optionflag ``EXCEPTION_2TO3`` to normalize exception class names
+  in traceback output. In Python 3 they are displayed as the full dotted name.
+  In Python 2 they are displayed as "just" the class name.  When running
+  doctests in Python 3, the optionflag will not have any effect, however when
+  running the same test in Python 2, the segments in the full dotted name
+  leading up to the class name are stripped away from the "expected" string.
+
 4.5.0 (2015-09-02)
 ------------------
 

src/zope/testing/renormalizing.py

@@ -11,13 +11,27 @@
 # FOR A PARTICULAR PURPOSE.
 #
 ##############################################################################
+import sys
 import doctest
 
+
+EXCEPTION_2TO3 = doctest.register_optionflag('EXCEPTION_2TO3')
+EXCEPTION_2TO3_HINT = """\
+===============================================================
+HINT:
+  You seem to test traceback output.
+  The optionflag EXCEPTION_2TO3 is set.
+  Do you use the full dotted name for the exception class name?
+==============================================================="""
+
+
 class OutputChecker(doctest.OutputChecker):
     """Pattern-normalizing outout checker
     """
 
-    def __init__(self, patterns):
+    def __init__(self, patterns=None):
+        if patterns is None:
+            patterns = []
         self.transformers = list(map(self._cook, patterns))
 
     def __add__(self, other):
@@ -39,6 +53,10 @@ def check_output(self, want, got, optionflags):
             want = transformer(want)
             got = transformer(got)
 
+        if sys.version < '3':
+            if optionflags & EXCEPTION_2TO3:
+                want = strip_dottedname_from_traceback(want)
+
         return doctest.OutputChecker.check_output(self, want, got, optionflags)
 
     def output_difference(self, example, got, optionflags):
@@ -62,6 +80,12 @@ def output_difference(self, example, got, optionflags):
 
         # temporarily hack example with normalized want:
         example.want = want
+
+        if sys.version < '3':
+            if optionflags & EXCEPTION_2TO3:
+                if maybe_a_traceback(got) is not None:
+                    got += EXCEPTION_2TO3_HINT
+
         result = doctest.OutputChecker.output_difference(
             self, example, got, optionflags)
         example.want = original
@@ -70,3 +94,31 @@ def output_difference(self, example, got, optionflags):
 
 RENormalizing = OutputChecker
 
+
+def maybe_a_traceback(string):
+    if not string:
+        return None
+
+    lines = string.splitlines()
+    last = lines[-1]
+    words = last.split(' ')
+    first = words[0]
+    if not first.endswith(':'):
+        return None
+
+    return lines, last, words, first
+
+
+def strip_dottedname_from_traceback(string):
+    # We might want to confirm more strictly were dealing with a traceback.
+    # We'll assume so for now.
+    maybe = maybe_a_traceback(string)
+    if maybe is None:
+        return string
+
+    lines, last, words, first = maybe
+    name = first.split('.')[-1]
+    words[0] = name
+    last = ' '.join(words)
+    lines[-1] = last
+    return '\n'.join(lines)

src/zope/testing/renormalizing.txt

@@ -234,3 +234,59 @@ Combining a checker with something else does not work:
         ...
     TypeError: unsupported operand type(s) for +: ...
 
+Using the 2to3 exception normalization:
+
+    >>> from zope.testing.renormalizing import EXCEPTION_2TO3
+    >>> checker = OutputChecker()
+    >>> want = """\
+    ... Traceback (most recent call last):
+    ... foo.bar.FooBarError: requires at least one argument."""
+    >>> got = """\
+    ... Traceback (most recent call last):
+    ... FooBarError: requires at least one argument."""
+    >>> result = checker.check_output(want, got, EXCEPTION_2TO3)
+    >>> import sys
+    >>> if sys.version < '3':
+    ...     expected = True
+    ... else:
+    ...     expected = False
+    >>> result == expected
+    True
+
+When reporting a failing test and running in Python 2, the normalizer tries
+to be helpful by explaining how to test for exceptions in the traceback output.
+
+    >>> want = """\
+    ... Traceback (most recent call last):
+    ... foo.bar.FooBarErrorXX: requires at least one argument.
+    ... """
+    >>> got = """\
+    ... Traceback (most recent call last):
+    ... FooBarError: requires at least one argument.
+    ... """
+    >>> checker.check_output(want, got, EXCEPTION_2TO3)
+    False
+    >>> from doctest import Example
+    >>> example = Example('dummy', want)
+    >>> result = checker.output_difference(example, got, EXCEPTION_2TO3)
+    >>> output = """\
+    ... Expected:
+    ...     Traceback (most recent call last):
+    ...     foo.bar.FooBarErrorXX: requires at least one argument.
+    ... Got:
+    ...     Traceback (most recent call last):
+    ...     FooBarError: requires at least one argument.
+    ... """
+    >>> hint = """\
+    ...     ===============================================================
+    ...     HINT:
+    ...       You seem to test traceback output.
+    ...       The optionflag EXCEPTION_2TO3 is set.
+    ...       Do you use the full dotted name for the exception class name?
+    ...     ==============================================================="""
+    >>> if sys.version < '3':
+    ...     expected = output + hint
+    ... else:
+    ...     expected = output
+    >>> result == expected
+    True

src/zope/testing/test_renormalizing.py

@@ -0,0 +1,54 @@
+import unittest
+
+from zope.testing.renormalizing import strip_dottedname_from_traceback
+
+
+class Exception2To3(unittest.TestCase):
+
+    def test_strip_dottedname(self):
+        string = """\
+Traceback (most recent call last):
+foo.bar.FooBarError: requires at least one argument."""
+        expected = """\
+Traceback (most recent call last):
+FooBarError: requires at least one argument."""
+        self.assertEqual(expected, strip_dottedname_from_traceback(string))
+
+    def test_no_dots_in_name(self):
+        string = """\
+Traceback (most recent call last):
+FooBarError: requires at least one argument."""
+        expected = """\
+Traceback (most recent call last):
+FooBarError: requires at least one argument."""
+        self.assertEqual(expected, strip_dottedname_from_traceback(string))
+
+    def test_no_colon_in_first_word(self):
+        string = """\
+Traceback (most recent call last):
+foo.bar.FooBarError requires at least one argument."""
+        expected = """\
+Traceback (most recent call last):
+foo.bar.FooBarError requires at least one argument."""
+        self.assertEqual(expected, strip_dottedname_from_traceback(string))
+
+    def test_input_empty(self):
+        string = ''
+        expected = ''
+        self.assertEqual(expected, strip_dottedname_from_traceback(string))
+
+    def test_input_spaces(self):
+        string = '   '
+        expected = '   '
+        self.assertEqual(expected, strip_dottedname_from_traceback(string))
+
+    def test_last_line_empty(self):
+        string = """\
+Traceback (most recent call last):
+
+"""
+        expected = """\
+Traceback (most recent call last):
+
+"""
+        self.assertEqual(expected, strip_dottedname_from_traceback(string))

src/zope/testing/tests.py

@@ -16,6 +16,7 @@
 import re
 import unittest
 from zope.testing import renormalizing
+from zope.testing.test_renormalizing import Exception2To3
 
 def print_(*args):
     sys.stdout.write(' '.join(map(str, args))+'\n')
@@ -57,4 +58,6 @@ def test_suite():
     if sys.version < '3':
         suite.addTests(doctest.DocTestSuite('zope.testing.server'))
         suite.addTests(doctest.DocFileSuite('formparser.txt'))
+    suite.addTest(
+        unittest.makeSuite(Exception2To3))
     return suite