fix #4386 - restructure construction and partial state of ExceptionInfo

changelog/4386.feature.rst

@@ -0,0 +1 @@
+Restructure ExceptionInfo object construction and ensure incomplete instances have a ``repr``/``str``.

src/_pytest/_code/code.py

@@ -391,40 +391,85 @@ def recursionindex(self):
 )
 
 
+@attr.s(repr=False)
 class ExceptionInfo(object):
     """ wraps sys.exc_info() objects and offers
         help for navigating the traceback.
     """
 
-    _striptext = ""
     _assert_start_repr = (
         "AssertionError(u'assert " if _PY2 else "AssertionError('assert "
     )
 
-    def __init__(self, tup=None, exprinfo=None):
-        import _pytest._code
+    _excinfo = attr.ib()
+    _striptext = attr.ib(default="")
+    _traceback = attr.ib(default=None)
+
+    @classmethod
+    def from_current(cls, exprinfo=None):
+        """returns a exceptioninfo matching the current traceback
+
+        .. warning::
+
+            experimental api
+
+
+        :param exprinfo: an text string helping to determine if we should
+                         strip assertionerror from the output, defaults
+                        to the exception message/__str__()
+
+        """
+        tup = sys.exc_info()
+        _striptext = ""
+        if exprinfo is None and isinstance(tup[1], AssertionError):
+            exprinfo = getattr(tup[1], "msg", None)
+            if exprinfo is None:
+                exprinfo = py.io.saferepr(tup[1])
+            if exprinfo and exprinfo.startswith(cls._assert_start_repr):
+                _striptext = "AssertionError: "
+
+        return cls(tup, _striptext)
+
+    @classmethod
+    def for_later(cls):
+        """return an unfilled ExceptionInfo
+        """
+        return cls(None)
+
+    @property
+    def type(self):
+        """the exception class"""
+        return self._excinfo[0]
+
+    @property
+    def value(self):
+        """the exception value"""
+        return self._excinfo[1]
+
+    @property
+    def tb(self):
+        """the exception raw traceback"""
+        return self._excinfo[2]
+
+    @property
+    def typename(self):
+        """the type name of the exception"""
+        return self.type.__name__
+
+    @property
+    def traceback(self):
+        """the traceback"""
+        if self._traceback is None:
+            self._traceback = Traceback(self.tb, excinfo=ref(self))
+        return self._traceback
 
-        if tup is None:
-            tup = sys.exc_info()
-            if exprinfo is None and isinstance(tup[1], AssertionError):
-                exprinfo = getattr(tup[1], "msg", None)
-                if exprinfo is None:
-                    exprinfo = py.io.saferepr(tup[1])
-                if exprinfo and exprinfo.startswith(self._assert_start_repr):
-                    self._striptext = "AssertionError: "
-        self._excinfo = tup
-        #: the exception class
-        self.type = tup[0]
-        #: the exception instance
-        self.value = tup[1]
-        #: the exception raw traceback
-        self.tb = tup[2]
-        #: the exception type name
-        self.typename = self.type.__name__
-        #: the exception traceback (_pytest._code.Traceback instance)
-        self.traceback = _pytest._code.Traceback(self.tb, excinfo=ref(self))
+    @traceback.setter
+    def traceback(self, value):
+        self._traceback = value
 
     def __repr__(self):
+        if self._excinfo is None:
+            return "<ExceptionInfo for raises contextmanager>"
         return "<ExceptionInfo %s tblen=%d>" % (self.typename, len(self.traceback))
 
     def exconly(self, tryshort=False):
@@ -513,6 +558,8 @@ def getrepr(
         return fmt.repr_excinfo(self)
 
     def __str__(self):
+        if self._excinfo is None:
+            return repr(self)
         entry = self.traceback[-1]
         loc = ReprFileLocation(entry.path, entry.lineno + 1, self.exconly())
         return str(loc)

src/_pytest/assertion/util.py

@@ -155,7 +155,7 @@ def isiterable(obj):
         explanation = [
             u"(pytest_assertion plugin: representation of details failed.  "
             u"Probably an object has a faulty __repr__.)",
-            six.text_type(_pytest._code.ExceptionInfo()),
+            six.text_type(_pytest._code.ExceptionInfo.from_current()),
         ]
 
     if not explanation:

src/_pytest/main.py

@@ -188,7 +188,7 @@ def wrap_session(config, doit):
         except Failed:
             session.exitstatus = EXIT_TESTSFAILED
         except KeyboardInterrupt:
-            excinfo = _pytest._code.ExceptionInfo()
+            excinfo = _pytest._code.ExceptionInfo.from_current()
             exitstatus = EXIT_INTERRUPTED
             if initstate <= 2 and isinstance(excinfo.value, exit.Exception):
                 sys.stderr.write("{}: {}\n".format(excinfo.typename, excinfo.value.msg))
@@ -197,7 +197,7 @@ def wrap_session(config, doit):
             config.hook.pytest_keyboard_interrupt(excinfo=excinfo)
             session.exitstatus = exitstatus
         except:  # noqa
-            excinfo = _pytest._code.ExceptionInfo()
+            excinfo = _pytest._code.ExceptionInfo.from_current()
             config.notify_exception(excinfo, config.option)
             session.exitstatus = EXIT_INTERNALERROR
             if excinfo.errisinstance(SystemExit):

src/_pytest/python.py

@@ -450,7 +450,7 @@ def _importtestmodule(self):
             mod = self.fspath.pyimport(ensuresyspath=importmode)
         except SyntaxError:
             raise self.CollectError(
-                _pytest._code.ExceptionInfo().getrepr(style="short")
+                _pytest._code.ExceptionInfo.from_current().getrepr(style="short")
             )
         except self.fspath.ImportMismatchError:
             e = sys.exc_info()[1]
@@ -466,7 +466,7 @@ def _importtestmodule(self):
         except ImportError:
             from _pytest._code.code import ExceptionInfo
 
-            exc_info = ExceptionInfo()
+            exc_info = ExceptionInfo.from_current()
             if self.config.getoption("verbose") < 2:
                 exc_info.traceback = exc_info.traceback.filter(filter_traceback)
             exc_repr = (

src/_pytest/python_api.py

@@ -684,13 +684,13 @@ def raises(expected_exception, *args, **kwargs):
             # XXX didn't mean f_globals == f_locals something special?
             #     this is destroyed here ...
         except expected_exception:
-            return _pytest._code.ExceptionInfo()
+            return _pytest._code.ExceptionInfo.from_current()
     else:
         func = args[0]
         try:
             func(*args[1:], **kwargs)
         except expected_exception:
-            return _pytest._code.ExceptionInfo()
+            return _pytest._code.ExceptionInfo.from_current()
     fail(message)
 
 
@@ -705,7 +705,7 @@ def __init__(self, expected_exception, message, match_expr):
         self.excinfo = None
 
     def __enter__(self):
-        self.excinfo = object.__new__(_pytest._code.ExceptionInfo)
+        self.excinfo = _pytest._code.ExceptionInfo.for_later()
         return self.excinfo
 
     def __exit__(self, *tp):

src/_pytest/runner.py

@@ -211,12 +211,12 @@ def __init__(self, func, when, treat_keyboard_interrupt_as_exception=False):
             self.result = func()
         except KeyboardInterrupt:
             if treat_keyboard_interrupt_as_exception:
-                self.excinfo = ExceptionInfo()
+                self.excinfo = ExceptionInfo.from_current()
             else:
                 self.stop = time()
                 raise
         except:  # noqa
-            self.excinfo = ExceptionInfo()
+            self.excinfo = ExceptionInfo.from_current()
         self.stop = time()
 
     def __repr__(self):

src/_pytest/unittest.py

@@ -115,6 +115,10 @@ def _addexcinfo(self, rawexcinfo):
         rawexcinfo = getattr(rawexcinfo, "_rawexcinfo", rawexcinfo)
         try:
             excinfo = _pytest._code.ExceptionInfo(rawexcinfo)
+            # invoke the attributes to trigger storing the traceback
+            # trial causes some issue there
+            excinfo.value
+            excinfo.traceback
         except TypeError:
             try:
                 try:
@@ -136,7 +140,7 @@ def _addexcinfo(self, rawexcinfo):
             except KeyboardInterrupt:
                 raise
             except fail.Exception:
-                excinfo = _pytest._code.ExceptionInfo()
+                excinfo = _pytest._code.ExceptionInfo.from_current()
         self.__dict__.setdefault("_excinfo", []).append(excinfo)
 
     def addError(self, testcase, rawexcinfo):

testing/code/test_code.py

@@ -169,7 +169,7 @@ def test_bad_getsource(self):
             else:
                 assert False
         except AssertionError:
-            exci = _pytest._code.ExceptionInfo()
+            exci = _pytest._code.ExceptionInfo.from_current()
         assert exci.getrepr()
 
 
@@ -181,7 +181,7 @@ def test_getsource(self):
             else:
                 assert False
         except AssertionError:
-            exci = _pytest._code.ExceptionInfo()
+            exci = _pytest._code.ExceptionInfo.from_current()
         entry = exci.traceback[0]
         source = entry.getsource()
         assert len(source) == 6

testing/code/test_excinfo.py

@@ -71,7 +71,7 @@ def test_excinfo_simple():
     try:
         raise ValueError
     except ValueError:
-        info = _pytest._code.ExceptionInfo()
+        info = _pytest._code.ExceptionInfo.from_current()
     assert info.type == ValueError
 
 
@@ -85,7 +85,7 @@ def f():
     try:
         f()
     except ValueError:
-        excinfo = _pytest._code.ExceptionInfo()
+        excinfo = _pytest._code.ExceptionInfo.from_current()
     linenumbers = [
         _pytest._code.getrawcode(f).co_firstlineno - 1 + 4,
         _pytest._code.getrawcode(f).co_firstlineno - 1 + 1,
@@ -126,7 +126,7 @@ def setup_method(self, method):
         try:
             h()
         except ValueError:
-            self.excinfo = _pytest._code.ExceptionInfo()
+            self.excinfo = _pytest._code.ExceptionInfo.from_current()
 
     def test_traceback_entries(self):
         tb = self.excinfo.traceback
@@ -163,7 +163,7 @@ def xyz():
         try:
             exec(source.compile())
         except NameError:
-            tb = _pytest._code.ExceptionInfo().traceback
+            tb = _pytest._code.ExceptionInfo.from_current().traceback
             print(tb[-1].getsource())
             s = str(tb[-1].getsource())
             assert s.startswith("def xyz():\n    try:")
@@ -356,6 +356,12 @@ def test_excinfo_str():
     assert len(s.split(":")) >= 3  # on windows it's 4
 
 
+def test_excinfo_for_later():
+    e = ExceptionInfo.for_later()
+    assert "for raises" in repr(e)
+    assert "for raises" in str(e)
+
+
 def test_excinfo_errisinstance():
     excinfo = pytest.raises(ValueError, h)
     assert excinfo.errisinstance(ValueError)
@@ -365,7 +371,7 @@ def test_excinfo_no_sourcecode():
     try:
         exec("raise ValueError()")
     except ValueError:
-        excinfo = _pytest._code.ExceptionInfo()
+        excinfo = _pytest._code.ExceptionInfo.from_current()
     s = str(excinfo.traceback[-1])
     assert s == "  File '<string>':1 in <module>\n  ???\n"
 
@@ -390,7 +396,7 @@ def test_entrysource_Queue_example():
     try:
         queue.Queue().get(timeout=0.001)
     except queue.Empty:
-        excinfo = _pytest._code.ExceptionInfo()
+        excinfo = _pytest._code.ExceptionInfo.from_current()
     entry = excinfo.traceback[-1]
     source = entry.getsource()
     assert source is not None
@@ -402,7 +408,7 @@ def test_codepath_Queue_example():
     try:
         queue.Queue().get(timeout=0.001)
     except queue.Empty:
-        excinfo = _pytest._code.ExceptionInfo()
+        excinfo = _pytest._code.ExceptionInfo.from_current()
     entry = excinfo.traceback[-1]
     path = entry.path
     assert isinstance(path, py.path.local)
@@ -453,7 +459,7 @@ def excinfo_from_exec(self, source):
         except KeyboardInterrupt:
             raise
         except:  # noqa
-            return _pytest._code.ExceptionInfo()
+            return _pytest._code.ExceptionInfo.from_current()
         assert 0, "did not raise"
 
     def test_repr_source(self):
@@ -491,7 +497,7 @@ def test_repr_source_not_existing(self):
         try:
             exec(co)
         except ValueError:
-            excinfo = _pytest._code.ExceptionInfo()
+            excinfo = _pytest._code.ExceptionInfo.from_current()
         repr = pr.repr_excinfo(excinfo)
         assert repr.reprtraceback.reprentries[1].lines[0] == ">   ???"
         if sys.version_info[0] >= 3:
@@ -510,7 +516,7 @@ def test_repr_many_line_source_not_existing(self):
         try:
             exec(co)
         except ValueError:
-            excinfo = _pytest._code.ExceptionInfo()
+            excinfo = _pytest._code.ExceptionInfo.from_current()
         repr = pr.repr_excinfo(excinfo)
         assert repr.reprtraceback.reprentries[1].lines[0] == ">   ???"
         if sys.version_info[0] >= 3:
@@ -1340,7 +1346,7 @@ def test_repr_traceback_with_unicode(style, encoding):
     try:
         raise RuntimeError(msg)
     except RuntimeError:
-        e_info = ExceptionInfo()
+        e_info = ExceptionInfo.from_current()
     formatter = FormattedExcinfo(style=style)
     repr_traceback = formatter.repr_traceback(e_info)
     assert repr_traceback is not None

testing/test_resultlog.py

@@ -151,7 +151,7 @@ def test_internal_exception(self, style):
         try:
             raise ValueError
         except ValueError:
-            excinfo = _pytest._code.ExceptionInfo()
+            excinfo = _pytest._code.ExceptionInfo.from_current()
         reslog = ResultLog(None, py.io.TextIO())
         reslog.pytest_internalerror(excinfo.getrepr(style=style))
         entry = reslog.logfile.getvalue()