Bug report

Bug description:

Consider the scenario where updatecache is called with a frozen module and module_globals is None.

In that case, _source_unavailable returns false because it is a frozen module, but because module_globals is None, the code carries on to look for the 'file' <frozen module> everywhere in sys.path. Compare that to the behavior prior to #132662 where that frozen module would simply return unavailable. I would recommend the following change:

    if filename.startswith("<frozen ") and module_globals is not None:
        # This is a frozen module, so we need to use the filename
        # from the module globals.
        fullname = module_globals.get("__file__")
        if fullname is None:
            print("fullname none")
            return []

Into

    if filename.startswith("<frozen "):
        if module_globals is None:
            return []
        # This is a frozen module, so we need to use the filename
        # from the module globals.
        fullname = module_globals.get("__file__")
        if fullname is None:
            print("fullname none")
            return []

For context, this is a problem for us because we run in a sandbox which restricts many OS operations, and this is performing useless os operations where it didn't prior to 3.14.

If there is agreement and it is helpful, happy to contribute a PR for this small change.

CPython versions tested on:

3.14

Operating systems tested on:

macOS, Windows, Linux

Linked PRs

• gh-140228: Linecache source is unavailable for frozen modules when global modules is None #140377
• [3.14] gh-140228: Avoid making unnecessary syscalls in linecache for frozen modules (GH-140377) #140738