Merge pull request #1486 from roolebo/fix-issue-138

Fix issue #138 - support chained exceptions

AUTHORS

@@ -75,6 +75,7 @@ Piotr Banaszkiewicz
 Punyashloka Biswal
 Ralf Schmitt
 Raphael Pierzina
+Roman Bolshakov
 Ronny Pfannschmidt
 Ross Lawley
 Ryan Wooden

CHANGELOG.rst

@@ -98,11 +98,13 @@
 
 * Fix (`#649`_): parametrized test nodes cannot be specified to run on the command line.
 
+* Fix (`#138`_): better reporting for python 3.3+ chained exceptions
 
 .. _#1437: https://github.com/pytest-dev/pytest/issues/1437
 .. _#469: https://github.com/pytest-dev/pytest/issues/469
 .. _#1431: https://github.com/pytest-dev/pytest/pull/1431
 .. _#649: https://github.com/pytest-dev/pytest/issues/649
+.. _#138: https://github.com/pytest-dev/pytest/issues/138
 
 .. _@asottile: https://github.com/asottile
 

_pytest/_code/code.py

@@ -608,12 +608,36 @@ class FormattedExcinfo(object):
                 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 repr_excinfo(self, excinfo):
+        if sys.version_info[0] < 3:
+            reprtraceback = self.repr_traceback(excinfo)
+            reprcrash = excinfo._getreprcrash()
+
+            return ReprExceptionInfo(reprtraceback, reprcrash)
+        else:
+            repr_chain = []
+            e = excinfo.value
+            descr = None
+            while e is not None:
+                reprtraceback = self.repr_traceback(excinfo)
+                reprcrash = excinfo._getreprcrash()
+                repr_chain += [(reprtraceback, reprcrash, descr)]
+                if e.__cause__ is not None:
+                    e = e.__cause__
+                    excinfo = ExceptionInfo((type(e), e, e.__traceback__))
+                    descr = 'The above exception was the direct cause of the following exception:'
+                elif e.__context__ is not None:
+                    e = e.__context__
+                    excinfo = ExceptionInfo((type(e), e, e.__traceback__))
+                    descr = 'During handling of the above exception, another exception occurred:'
+                else:
+                    e = None
+            repr_chain.reverse()
+            return ExceptionChainRepr(repr_chain)
+
+
+class TerminalRepr(object):
     def __str__(self):
         s = self.__unicode__()
         if sys.version_info[0] < 3:
@@ -632,21 +656,47 @@ class TerminalRepr:
         return "<%s instance at %0x>" %(self.__class__, id(self))
 
 
-class ReprExceptionInfo(TerminalRepr):
+class ExceptionRepr(TerminalRepr):
-    def __init__(self, reprtraceback, reprcrash):
+    def __init__(self):
-        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 ExceptionChainRepr(ExceptionRepr):
+    def __init__(self, chain):
+        super(ExceptionChainRepr, self).__init__()
+        self.chain = chain
+        # reprcrash and reprtraceback of the outermost (the newest) exception
+        # in the chain
+        self.reprtraceback = chain[-1][0]
+        self.reprcrash = chain[-1][1]
+
+    def toterminal(self, tw):
+        for element in self.chain:
+            element[0].toterminal(tw)
+            if element[2] is not None:
+                tw.line("")
+                tw.line(element[2], yellow=True)
+        super(ExceptionChainRepr, self).toterminal(tw)
+
+
+class ReprExceptionInfo(ExceptionRepr):
+    def __init__(self, reprtraceback, reprcrash):
+        super(ReprExceptionInfo, self).__init__()
+        self.reprtraceback = reprtraceback
+        self.reprcrash = reprcrash
+
+    def toterminal(self, tw):
+        self.reprtraceback.toterminal(tw)
+        super(ReprExceptionInfo, self).toterminal(tw)
+
 class ReprTraceback(TerminalRepr):
     entrysep = "_ "
 

_pytest/runner.py

@@ -494,9 +494,13 @@ def importorskip(modname, minversion=None):
     """
     __tracebackhide__ = True
     compile(modname, '', 'eval') # to catch syntaxerrors
+    should_skip = False
     try:
         __import__(modname)
     except ImportError:
+        # Do not raise chained exception here(#1485)
+        should_skip = True
+    if should_skip:
         skip("could not import %r" %(modname,))
     mod = sys.modules[modname]
     if minversion is None:

testing/code/test_excinfo.py

@@ -3,7 +3,8 @@
 import _pytest
 import py
 import pytest
-from _pytest._code.code import FormattedExcinfo, ReprExceptionInfo
+from _pytest._code.code import (FormattedExcinfo, ReprExceptionInfo,
+        ExceptionChainRepr)
 
 queue = py.builtin._tryimport('queue', 'Queue')
 
@@ -404,6 +405,8 @@ class TestFormattedExcinfo:
             excinfo = _pytest._code.ExceptionInfo()
         repr = pr.repr_excinfo(excinfo)
         assert repr.reprtraceback.reprentries[1].lines[0] == ">   ???"
+        if py.std.sys.version_info[0] >= 3:
+            assert repr.chain[0][0].reprentries[1].lines[0] == ">   ???"
 
     def test_repr_many_line_source_not_existing(self):
         pr = FormattedExcinfo()
@@ -417,6 +420,8 @@ raise ValueError()
             excinfo = _pytest._code.ExceptionInfo()
         repr = pr.repr_excinfo(excinfo)
         assert repr.reprtraceback.reprentries[1].lines[0] == ">   ???"
+        if py.std.sys.version_info[0] >= 3:
+            assert repr.chain[0][0].reprentries[1].lines[0] == ">   ???"
 
     def test_repr_source_failing_fullsource(self):
         pr = FormattedExcinfo()
@@ -449,6 +454,7 @@ raise ValueError()
 
         class FakeExcinfo(_pytest._code.ExceptionInfo):
             typename = "Foo"
+            value = Exception()
             def __init__(self):
                 pass
 
@@ -466,10 +472,15 @@ raise ValueError()
         fail = IOError()  # noqa
         repr = pr.repr_excinfo(excinfo)
         assert repr.reprtraceback.reprentries[0].lines[0] == ">   ???"
+        if py.std.sys.version_info[0] >= 3:
+            assert repr.chain[0][0].reprentries[0].lines[0] == ">   ???"
+
 
         fail = py.error.ENOENT  # noqa
         repr = pr.repr_excinfo(excinfo)
         assert repr.reprtraceback.reprentries[0].lines[0] == ">   ???"
+        if py.std.sys.version_info[0] >= 3:
+            assert repr.chain[0][0].reprentries[0].lines[0] == ">   ???"
 
 
     def test_repr_local(self):
@@ -656,6 +667,9 @@ raise ValueError()
             repr = p.repr_excinfo(excinfo)
             assert repr.reprtraceback
             assert len(repr.reprtraceback.reprentries) == len(reprtb.reprentries)
+            if py.std.sys.version_info[0] >= 3:
+                assert repr.chain[0][0]
+                assert len(repr.chain[0][0].reprentries) == len(reprtb.reprentries)
             assert repr.reprcrash.path.endswith("mod.py")
             assert repr.reprcrash.message == "ValueError: 0"
 
@@ -746,8 +760,13 @@ raise ValueError()
         for style in ("short", "long", "no"):
             for showlocals in (True, False):
                 repr = excinfo.getrepr(style=style, showlocals=showlocals)
-                assert isinstance(repr, ReprExceptionInfo)
+                if py.std.sys.version_info[0] < 3:
+                    assert isinstance(repr, ReprExceptionInfo)
                 assert repr.reprtraceback.style == style
+                if py.std.sys.version_info[0] >= 3:
+                    assert isinstance(repr, ExceptionChainRepr)
+                    for repr in repr.chain:
+                        assert repr[0].style == style
 
     def test_reprexcinfo_unicode(self):
         from _pytest._code.code import TerminalRepr
@@ -928,3 +947,70 @@ raise ValueError()
         assert tw.lines[14] == "E       ValueError"
         assert tw.lines[15] == ""
         assert tw.lines[16].endswith("mod.py:9: ValueError")
+
+    @pytest.mark.skipif("sys.version_info[0] < 3")
+    def test_exc_chain_repr(self, importasmod):
+        mod = importasmod("""
+            class Err(Exception):
+                pass
+            def f():
+                try:
+                    g()
+                except Exception as e:
+                    raise Err() from e
+                finally:
+                    h()
+            def g():
+                raise ValueError()
+
+            def h():
+                raise AttributeError()
+        """)
+        excinfo = pytest.raises(AttributeError, mod.f)
+        r = excinfo.getrepr(style="long")
+        tw = TWMock()
+        r.toterminal(tw)
+        for line in tw.lines: print (line)
+        assert tw.lines[0]  == ""
+        assert tw.lines[1]  == "    def f():"
+        assert tw.lines[2]  == "        try:"
+        assert tw.lines[3]  == ">           g()"
+        assert tw.lines[4]  == ""
+        assert tw.lines[5].endswith("mod.py:6: ")
+        assert tw.lines[6]  == ("_ ", None)
+        assert tw.lines[7]  == ""
+        assert tw.lines[8]  == "    def g():"
+        assert tw.lines[9]  == ">       raise ValueError()"
+        assert tw.lines[10] == "E       ValueError"
+        assert tw.lines[11] == ""
+        assert tw.lines[12].endswith("mod.py:12: ValueError")
+        assert tw.lines[13] == ""
+        assert tw.lines[14] == "The above exception was the direct cause of the following exception:"
+        assert tw.lines[15] == ""
+        assert tw.lines[16] == "    def f():"
+        assert tw.lines[17] == "        try:"
+        assert tw.lines[18] == "            g()"
+        assert tw.lines[19] == "        except Exception as e:"
+        assert tw.lines[20] == ">           raise Err() from e"
+        assert tw.lines[21] == "E           test_exc_chain_repr0.mod.Err"
+        assert tw.lines[22] == ""
+        assert tw.lines[23].endswith("mod.py:8: Err")
+        assert tw.lines[24] == ""
+        assert tw.lines[25] == "During handling of the above exception, another exception occurred:"
+        assert tw.lines[26] == ""
+        assert tw.lines[27] == "    def f():"
+        assert tw.lines[28] == "        try:"
+        assert tw.lines[29] == "            g()"
+        assert tw.lines[30] == "        except Exception as e:"
+        assert tw.lines[31] == "            raise Err() from e"
+        assert tw.lines[32] == "        finally:"
+        assert tw.lines[33] == ">           h()"
+        assert tw.lines[34] == ""
+        assert tw.lines[35].endswith("mod.py:10: ")
+        assert tw.lines[36] == ('_ ', None)
+        assert tw.lines[37] == ""
+        assert tw.lines[38] == "    def h():"
+        assert tw.lines[39] == ">       raise AttributeError()"
+        assert tw.lines[40] == "E       AttributeError"
+        assert tw.lines[41] == ""
+        assert tw.lines[42].endswith("mod.py:15: AttributeError")