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

從 pdb 現有的 break 和 clear 命令處理開始，比較 filename:lineno 和 function 的解析路徑。使用 b main:foo 重現 main.py 範例，然後確認 filename:function 能夠正常運作，且不會導致現有形式回歸；該 issue 引用了相關的 PR gh-142470。