- Fixed bug where some exception re-raise scenarios would attach

the exception to itself as the "cause"; while the Python 3 interpreter
is OK with this, it could cause endless loops in iPython.
fixes #3625
- add tests for reraise, raise_from_cause
- raise_from_cause is the same on py2k/3k, use just one function

1 files changed, 59 insertions, 0 deletions

diff --git a/test/base/test_utils.py b/test/base/test_utils.py
index 4370d612b..6d162ff4d 100644
--- a/test/base/test_utils.py
+++ b/test/base/test_utils.py
@@ -1,4 +1,5 @@
 import copy
+import sys
 
 from sqlalchemy import util, sql, exc, testing
 from sqlalchemy.testing import assert_raises, assert_raises_message, fixtures
@@ -2134,6 +2135,64 @@ class TestClassHierarchy(fixtures.TestBase):
             eq_(set(util.class_hierarchy(A)), set((A, B, object)))
 
 
+class ReraiseTest(fixtures.TestBase):
+    @testing.requires.python3
+    def test_raise_from_cause_same_cause(self):
+        class MyException(Exception):
+            pass
+
+        def go():
+            try:
+                raise MyException("exc one")
+            except Exception as err:
+                util.raise_from_cause(err)
+
+        try:
+            go()
+            assert False
+        except MyException as err:
+            is_(err.__cause__, None)
+
+    def test_reraise_disallow_same_cause(self):
+        class MyException(Exception):
+            pass
+
+        def go():
+            try:
+                raise MyException("exc one")
+            except Exception as err:
+                type_, value, tb = sys.exc_info()
+                util.reraise(type_, err, tb, value)
+
+        assert_raises_message(
+            AssertionError,
+            "Same cause emitted",
+            go
+        )
+
+    def test_raise_from_cause(self):
+        class MyException(Exception):
+            pass
+
+        class MyOtherException(Exception):
+            pass
+
+        me = MyException("exc on")
+
+        def go():
+            try:
+                raise me
+            except Exception:
+                util.raise_from_cause(MyOtherException("exc two"))
+
+        try:
+            go()
+            assert False
+        except MyOtherException as moe:
+            if testing.requires.python3.enabled:
+                is_(moe.__cause__, me)
+
+
 class TestClassProperty(fixtures.TestBase):
 
     def test_simple(self):