bpo-43318: Fix a bug where pdb does not always echo cleared breakpoints.

[hjzin]

https://bugs.python.org/issue43318

In Pdb, when successfully clear breakpoints, the Pdb should output a message:"Deleted XXX", but when breakpoints are cleared by filename:lineno, the message can't be output.

I think it's related to the following code.

pdb.py:

def do_clear(self, arg):
    ...
  
    if ':' in arg:
        # Make sure it works for "clear C:\foo\bar.py:12"
        i = arg.rfind(':')
        filename = arg[:i]
        arg = arg[i+1:]
        try:
            lineno = int(arg)
        except ValueError:
            err = "Invalid line number (%s)" % arg
        else:
            bplist = self.get_breaks(filename, lineno)
            err = self.clear_break(filename, lineno)
        if err:
            self.error(err)
        else:
            for bp in bplist:
                self.message('Deleted %s' % bp)
        return

self.get_breaks is called to get the breakpoints to be deleted, the result is in bplist. self.clear_break is called to delete the breakpoints in bplist. Each element in bplist is a reference to a Breakpoint object, so when all Breakpoint objects are removed, the bplist will become an empty list when self.clear_break is called, so pdb can't output the prompt message.

It can be simply fixed by following code:

    bplist = self.get_breaks(filename, lineno)[:]

https://bugs.python.org/issue43318

[the-knights-who-say-ni]

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[github-actions]

This PR is stale because it has been open for 30 days with no activity.

[iritkatriel]

There are two news files - this one can be deleted.

[iritkatriel]

Please also resolve the merge conflict on test_pdb.py (rebase your branch).

[hjzin]

Please also resolve the merge conflict on test_pdb.py (rebase your branch).

I have rebased my branch, please review again.

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @iritkatriel for commit 0577eae 🤖

If you want to schedule another build, you need to add the ":hammer: test-with-buildbots" label again.

[iritkatriel]

Thank you @hjzin . This looks good now. I will merge once the tests have run.

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @iritkatriel for commit df58705 🤖

If you want to schedule another build, you need to add the ":hammer: test-with-buildbots" label again.

[miss-islington]

Thanks @hjzin for the PR, and @iritkatriel for merging it 🌮🎉.. I'm working now to backport this PR to: 3.10, 3.9.
🐍🍒⛏🤖

[bedevere-bot]

GH-26674 is a backport of this pull request to the 3.10 branch.

[bedevere-bot]

GH-26675 is a backport of this pull request to the 3.9 branch.