gh-148615: Handle -- end-of-options separator in pdb argument parsing

[Shrey-N]

The switch from getopt to argparse in gh-125115, python -m pdb rejects the standard -- end-of-options separator. Makes it impossible to pass arguments that share names with pdb flags (like -c) to the target script.

The root cause is that pdb's argparse parser has no positional arguments defined, so parse_known_args() does not consume -- and returns it in the remainder list. The manual post processing logic in parse_args() then incorrectly treats it as an unrecognized flag since it starts with -.

This adds a check for -- in the elif args[0].startswith('-'). When found, the separator is consumed and parsing continues to the script name. If no script follows, an error is raised. All other unrecognized flags continue to produce the existing error message.

Closes gh-148615 :)

[gaogaotiantian]

Thanks for fixing this. We need some regression test on this. We need to test the specific case reported, and also some others. I wonder if -- works as expected when it's on other places.

For the code itself, let's move -- check to it's own case (not under args[0].startswith), less nested logic.

[Shrey-N]

Thank you, that makes sense, I will update the PR asap! :)

[Shrey-N]

Hiya @gaogaotiantian, is there anything else needed from my side to move this forward?

[gaogaotiantian]

Sorry I was kind of busy recently and did not get a chance to take a look :)

I don't think this issue worth a while new test class for it. Some test cases in a test method would do. The new test class does not cover anything that the integration test can't cover. Let's just put all the interesting test cases in the same method. It's a relatively corner case and we don't need to overreact.

[python-cla-bot]

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[Shrey-N]

Hiya @gaogaotiantian I followed your suggestion, and also simplified the news entry, the old one wasn't up to the mark

[gaogaotiantian]

What's the difference between the two test cases? It looks to me that they are testing similar things? Can we combine them together and maybe remove duplicated test cases?

[Shrey-N]

You are right @gaogaotiantian, I removed the redundant one (test_run_script_with_double_dash)

[read-the-docs-community]

Documentation build overview

📚 cpython-previews | 🛠️ Build #32526079 | 📁 Comparing c2a7d7f against main (55c9d60)

  🔍 Preview build  

5 files changed · ± 5 modified

± Modified

• library/difflib.html
• library/functions.html
• library/http.server.html
• library/tkinter.messagebox.html
• whatsnew/changelog.html

[gaogaotiantian]

Could you resolve the conflict?

[Shrey-N]

Sorry for the delay @gaogaotiantian, I think it's resolved now :)

[miss-islington-app]

Thanks @Shrey-N for the PR, and @gaogaotiantian for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

[miss-islington-app]

Sorry, @Shrey-N and @gaogaotiantian, I could not cleanly backport this to 3.14 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 970b0433f498fd0d048b1f50229a7f0fb4d9e07a 3.14

[bedevere-app]

GH-149442 is a backport of this pull request to the 3.14 branch.