Issue #16180: Exit pdb if file has syntax error, instead of trapping user

in an infinite loop.  Patch by Xavier de Gaye.

Lib/pdb.py

@@ -1322,6 +1322,9 @@ def main():
             # In most cases SystemExit does not warrant a post-mortem session.
             print "The program exited via sys.exit(). Exit status: ",
             print sys.exc_info()[1]
+        except SyntaxError:
+            traceback.print_exc()
+            sys.exit(1)
         except:
             traceback.print_exc()
             print "Uncaught exception. Entering post mortem debugging"

Lib/test/test_pdb.py

@@ -69,6 +69,17 @@ class PdbTestCase(unittest.TestCase):
             any('main.py(5)foo()->None' in l for l in stdout.splitlines()),
             'Fail to step into the caller after a return')
 
+    def test_issue16180(self):
+        # A syntax error in the debuggee.
+        script = "def f: pass\n"
+        commands = ''
+        expected = "SyntaxError:"
+        stdout, stderr = self.run_pdb(script, commands)
+        self.assertIn(expected, stdout,
+            '\n\nExpected:\n{}\nGot:\n{}\n'
+            'Fail to handle a syntax error in the debuggee.'
+            .format(expected, stdout))
+
 
 class PdbTestInput(object):
     """Context manager that makes testing Pdb in doctests easier."""

Misc/NEWS

@@ -37,6 +37,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #16180: Exit pdb if file has syntax error, instead of trapping user
+  in an infinite loop.  Patch by Xavier de Gaye.
+
 - Issue #22812: Fix unittest discovery examples.
   Patch from Pam McA'Nulty.