bpo-35931: Gracefully handle SyntaxError in pdb debug command (GH-11782)

Previously, `debug print(` would cause the interpreter to exit on a SyntaxError whereas `print(` would properly display the error and return to the pdb prompt.

This patch fixes this by pre-compiling the code before passing it to `Pdb.run`.


https://bugs.python.org/issue35931

1 files changed, 7 insertions, 1 deletions

diff --git a/Lib/pdb.py b/Lib/pdb.py
index 60bdb76..1443f9f 100755
--- a/Lib/pdb.py
+++ b/Lib/pdb.py
@@ -1093,10 +1093,16 @@ class Pdb(bdb.Bdb, cmd.Cmd):
         sys.settrace(None)
         globals = self.curframe.f_globals
         locals = self.curframe_locals
+        try:
+            code = compile(arg, "<string>", "exec")
+        except SyntaxError:
+            exc_info = sys.exc_info()[:2]
+            self.error(traceback.format_exception_only(*exc_info)[-1].strip())
+            return
         p = Pdb(self.completekey, self.stdin, self.stdout)
         p.prompt = "(%s) " % self.prompt.strip()
         self.message("ENTERING RECURSIVE DEBUGGER")
-        sys.call_tracing(p.run, (arg, globals, locals))
+        sys.call_tracing(p.run, (code, globals, locals))
         self.message("LEAVING RECURSIVE DEBUGGER")
         sys.settrace(self.trace_dispatch)
         self.lastcmd = p.lastcmd