do_debug: harden and fix for py38-dev (v3.8.0a2)

blueyed · blueyed · commit c6a4a374f967 · 2019-03-09T19:01:14.000+01:00
Based on python/cpython#12103.
diff --git a/pdb.py b/pdb.py
@@ -653,24 +653,6 @@ def do_pp(self, arg):
     do_pp.__doc__ = pdb.Pdb.do_pp.__doc__
 
     def do_debug(self, arg):
-        # Compile the code already to not crash on SyntaxErrors.
-        # Error handling is copied from pdb.Pdb.default.
-        # This will be fixed in cpython 3.7.3 (bpo-35931).
-        cmd = arg
-        if isinstance(cmd, str):
-            try:
-                cmd = compile(cmd, "<string>", "exec")
-            except SyntaxError:
-                import traceback
-                exc_info = sys.exc_info()[:2]
-                msg = traceback.format_exception_only(*exc_info)[-1].strip()
-                if hasattr(self, 'error'):
-                    self.error(msg)
-                else:
-                    # For py27.
-                    print('***', msg, file=self.stdout)
-                return
-
         # this is a hack (as usual :-))
         #
         # inside the original do_debug, there is a call to the global "Pdb" to
@@ -696,7 +678,14 @@ def __init__(self, *args):
             'Pdb': PdbppWithConfig,
         }
         orig_do_debug = rebind_globals(do_debug_func, updateglobals)
-        return orig_do_debug(self, cmd)
+
+        # Handle any exception, e.g. SyntaxErrors.
+        # This is about to be improved in Python itself (3.8, 3.7.3?).
+        try:
+            return orig_do_debug(self, arg)
+        except Exception:
+            exc_info = sys.exc_info()[:2]
+            self.error(traceback.format_exception_only(*exc_info)[-1].strip())
     do_debug.__doc__ = pdb.Pdb.do_debug.__doc__
 
     def do_interact(self, arg):
diff --git a/testing/test_pdb.py b/testing/test_pdb.py
@@ -1544,6 +1544,13 @@ def fn():
 
 
 def test_syntaxerror_in_command():
+    # Python 3.8.0a2 handles the SyntaxError itself.
+    # Ref/followup: https://github.com/python/cpython/pull/12103
+    if sys.version_info == (3, 8, 0, "alpha", 2):
+        expected_debug_err = "\\*\\*\\* SyntaxError: .*"
+    else:
+        expected_debug_err = "ENTERING RECURSIVE DEBUGGER\n\\*\\*\\* SyntaxError: .*"
+
     def f():
         set_trace()
 
@@ -1555,9 +1562,9 @@ def f():
 # print(
 \\*\\*\\* SyntaxError: .*
 # debug print(
-\\*\\*\\* SyntaxError: .*
+%s
 # c
-""")
+""" % expected_debug_err)
 
 
 def test_debug_with_overridden_continue():
