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Benjamin Peterson committed 76cf60e

normalize exceptions passed to the __exit__ method #7853

In Python 2.x, exceptions in finally blocks are not normalized. Since with
statements are implemented using finally blocks, ceval.c had to be tweaked to
distinguish between with finally blocks and normal ones.

A test for the finalization of generators containing with statements was also
added.

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  • Parent commits de5fa92
  • Branches legacy-trunk

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Files changed (5)

File Lib/test/test_generators.py

 >>> del g
 exiting
 
+>>> class context(object):
+...    def __enter__(self): pass
+...    def __exit__(self, *args): print 'exiting'
+>>> def f():
+...     with context():
+...          yield
+>>> g = f()
+>>> g.next()
+>>> del g
+exiting
+
 
 GeneratorExit is not caught by except Exception:
 

File Lib/test/test_with.py

         self.assertAfterWithManagerInvariantsWithError(cm)
         self.assertAfterWithGeneratorInvariantsWithError(self.resource)
 
-    @unittest.expectedFailure
     def testExceptionNormalized(self):
         cm = mock_contextmanager_generator()
         def shouldThrow():
 Core and Builtins
 -----------------
 
+- Issue #7853: Normalize exceptions before they are passed to a context managers
+  __exit__ method.
+
 - Issue #7385: Fix a crash in `MemoryView_FromObject` when
   `PyObject_GetBuffer` fails.  Patch by Florent Xicluna.
 

File Python/ceval.c

 			Py_DECREF(u);
 			if (!x)
 				break;
-			/* Setup the finally block before pushing the result
-			   of __enter__ on the stack. */
-			PyFrame_BlockSetup(f, SETUP_FINALLY, INSTR_OFFSET() + oparg,
+			/* Setup a finally block (SETUP_WITH as a block is
+			   equivalent to SETUP_FINALLY except it normalizes
+			   the exception) before pushing the result of
+			   __enter__ on the stack. */
+			PyFrame_BlockSetup(f, SETUP_WITH, INSTR_OFFSET() + oparg,
 					   STACK_LEVEL());
 
 			PUSH(x);
 			}
 			if (b->b_type == SETUP_FINALLY ||
 			    (b->b_type == SETUP_EXCEPT &&
-			     why == WHY_EXCEPTION)) {
+			     why == WHY_EXCEPTION) ||
+			    b->b_type == SETUP_WITH) {
 				if (why == WHY_EXCEPTION) {
 					PyObject *exc, *val, *tb;
 					PyErr_Fetch(&exc, &val, &tb);
 					   so a program can emulate the
 					   Python main loop.  Don't do
 					   this for 'finally'. */
-					if (b->b_type == SETUP_EXCEPT) {
+					if (b->b_type == SETUP_EXCEPT ||
+					    b->b_type == SETUP_WITH) {
 						PyErr_NormalizeException(
 							&exc, &val, &tb);
 						set_exc_info(tstate,

File Python/compile.c

 
     /* SETUP_WITH pushes a finally block. */
     compiler_use_next_block(c, block);
+    /* Note that the block is actually called SETUP_WITH in ceval.c, but
+       functions the same as SETUP_FINALLY except that exceptions are
+       normalized. */
     if (!compiler_push_fblock(c, FINALLY_TRY, block)) {
 	return 0;
     }