Commit 9f4e031b authored by Raphaël Hertzog's avatar Raphaël Hertzog Committed by Tim Graham
Browse files

Fixed #25761 -- Added __cause__.__traceback__ to reraised exceptions. 

When Django reraises an exception, it sets the __cause__ attribute even
in Python 2, mimicking Python's 3 behavior for "raise Foo from Bar".
However, Python 3 also ensures that all exceptions have a __traceback__
attribute and thus the "traceback2" Python 2 module (backport of Python
3's "traceback" module) relies on the fact that whenever you have a
__cause__ attribute, the recorded exception also has a __traceback__
attribute.

This is breaking testtools which is using traceback2 (see
https://github.com/testing-cabal/testtools/issues/162).

This commit fixes this inconsistency by ensuring that Django sets
the __traceback__ attribute on any exception stored in a __cause__
attribute of a reraised exception.
parent c6ea4ed5

django/db/migrations/loader.py

+2 −0
Original line number Diff line number Diff line
@@ -272,6 +272,8 @@ class MigrationLoader(object): 
                        ),

                        missing)

                    exc_value.__cause__ = exc

                    if not hasattr(exc, '__traceback__'):

                        exc.__traceback__ = sys.exc_info()[2]

                    six.reraise(NodeNotFoundError, exc_value, sys.exc_info()[2])

            raise exc

django/db/utils.py

+2 −0
Original line number Diff line number Diff line
@@ -85,6 +85,8 @@ class DatabaseErrorWrapper(object): 
            if issubclass(exc_type, db_exc_type):

                dj_exc_value = dj_exc_type(*exc_value.args)

                dj_exc_value.__cause__ = exc_value

                if not hasattr(exc_value, '__traceback__'):

                    exc_value.__traceback__ = traceback

                # Only set the 'errors_occurred' flag for errors that may make

                # the connection unusable.

                if dj_exc_type not in (DataError, IntegrityError):

django/utils/timezone.py

+2 −0
Original line number Diff line number Diff line
@@ -146,6 +146,8 @@ class LocalTimezone(ReferenceLocalTimezone): 
            exc_value = exc_type(

                "Unsupported value: %r. You should install pytz." % dt)

            exc_value.__cause__ = exc

            if not hasattr(exc, '__traceback__'):

                exc.__traceback__ = sys.exc_info()[2]

            six.reraise(exc_type, exc_value, sys.exc_info()[2])



utc = pytz.utc if pytz else UTC()

docs/ref/exceptions.txt

+7 −1
Original line number Diff line number Diff line
@@ -196,7 +196,13 @@ As per :pep:`3134`, a ``__cause__`` attribute is set with the original 
(underlying) database exception, allowing access to any additional

information provided. (Note that this attribute is available under

both Python 2 and Python 3, although :pep:`3134` normally only applies

to Python 3.)

to Python 3. To avoid unexpected differences with Python 3, Django will also

ensure that the exception made available via ``__cause__`` has a usable

``__traceback__`` attribute.)



.. versionchanged:: 1.10



    The ``__traceback__`` attribute described above was added.



.. exception:: models.ProtectedError