Merge pull request #1742 from takluyver/customexc-check-once

Check for custom_exceptions only once


We already catch custom exceptions in run_code and call the custom handler, but we were checking for them again in showtraceback. This just removes the second check, so custom exception handlers can safely call showtraceback().

IPython/core/interactiveshell.py

@@ -1703,9 +1703,6 b' class InteractiveShell(SingletonConfigurable):'
             elif etype is UsageError:
                 self.write_err("UsageError: %s" % value)
             else:
-                if etype in self.custom_exceptions:
-                    stb = self.CustomTB(etype, value, tb, tb_offset)
-                else:
                     if exception_only:
                         stb = ['An exception has occurred, use %tb to see '
                                'the full traceback.\n']

IPython/core/tests/test_interactiveshell.py

@@ -338,6 +338,21 b' class InteractiveShellTestCase(unittest.TestCase):'
                     parent = None)
         nt.assert_equal(find, info)
 
+    def test_custom_exception(self):
+        called = []
+        def my_handler(shell, etype, value, tb, tb_offset=None):
+            called.append(etype)
+            shell.showtraceback((etype, value, tb), tb_offset=tb_offset)
+        
+        ip.set_custom_exc((ValueError,), my_handler)
+        try:
+            ip.run_cell("raise ValueError('test')")
+            # Check that this was called, and only once.
+            self.assertEqual(called, [ValueError])
+        finally:
+            # Reset the custom exception hook
+            ip.set_custom_exc((), None)
+
 
 class TestSafeExecfileNonAsciiPath(unittest.TestCase):