[issue33944] Deprecate and remove pth files

[Nick Coghlan]

Nick Coghlan <ncoghlan at gmail.com> added the comment:

Brett pointed out that may initial reaction above came across as quite blunt and demanding, so attempting to phrase that more clearly as a user experience consideration:

It may be tempting to view this as purely a clean-up of the import system implementation, removing a quirky and error prone construct for the sake of improved maintainability of both the import system itself, and the maintainability of end user installations.

My request (wearing my "BDFL-delegate for packaging interoperability standards" hat) is that proponents of the change resist the temptation to view the problem that way :)

Path files are used extensively across the Python packaging ecosystem to implement additional environment management features beyond those provided natively by interpreter implementations, and while we've added native equivalents for some of them (namespace packages, virtual environments), we're far from having added support for all of them (dynamic package version selection, virtual environment chaining, editable package installs that still publish correct PEP 376 package metadata, etc).

This means that any changes in this area pose significant backwards compatibility risks, and need to be approached carefully, and cautiously, with a strong emphasis on surveying real world code and seeing how the feature is currently being used.

Or, alternatively, the idea can be broken up into smaller, lower impact changes that still help to address the import system and end user environment maintainability issues, but don't involve breaking backwards compatibility.

(For an example of the latter: if "python -m site --list-pth-files" printed a list of all of the pth files and "python -m site --dump-pth-files" listed both the files and their contents, then environment debuggability would improve significantly without any compatibility impacts whatsoever)

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