Feature: Support `filename:function` syntax for pdb break and clear command

Feature or enhancement

Proposal:

Currently, pdb's break command supports filename:lineno or just function (in the current context or imported modules). However, it does not support the filename:function syntax.

Attempting to use break filename:function usually results in a Error because pdb expects the part after the colon to be a line number.

main.py:

def foo():
    pass

bash-5.3# ./python -m pdb main.py
> /workspaces/cpython/main.py(1)<module>()
-> def foo():
(Pdb) b main:foo
*** Bad lineno: foo

This syntax is useful for specifying a function in a specific file, especially to disambiguate if multiple files have the same function name, or if the file hasn't been loaded yet but the user wants to be explicit.

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-142470

Start with pdb's existing break and clear command handling, comparing the filename:lineno and function resolution paths. Reproduce the main.py example with b main:foo, then verify that filename:function works without regressing the existing forms; the issue references linked PR gh-142470.