Feature or enhancement

Suggesting to add syntax for producing deprecation warnings for positional use of optional parameters.

I made aproof-of-concept patch for this where I introduced a new special symbolx. Example use:

/*[clinicinput]mod.funcstuff:object    /xoptarg:int=128

This will then generate code that emits a DeprecationWarning ifoptarg is passed as a positional argument, but not if it is passed as a keyword.

We can use this feature to introduce deprecation warnings for parameters that will become keyword-only in future releases. When the deprecation period is done, we can simply replace thex with*, to really make the optional params keyword-only.

Pitch

Quoting@serhiy-storchaka, in issue#93057:

It is recommended to make optional rarely used arguments keyword-only. I do not think it will break much code, but we need a deprecation period for this.

The problem is that sqlite3.connect() was converted to Argument Clinic, and it was much easier to add deprecation warning in the old code.

Previous discussion

• Make optional parameters of sqlite3.connect() keyword-only #93057

Linked PRs

• gh-95065: Add Argument Clinic support for deprecating positional use of parameters #95151
• gh-95065: Argument Clinic: Pretty-print long C strings in generated code #107712
• gh-95065: PoC: Argument Clinic: Support multiple '* [from ...]' deprecations #107742
• gh-95065: Make Argument Clinic append deprecation warnings to docstrings #107745
• gh-95065: Argument Clinic: Add comment to preprocessor warning code #107766
• gh-95065: Argument Clinic: Add functional tests of deprecated positionals #107768
• gh-95065: Produce nicer deprecation messages in Argument Clinic #107808
• gh-95065, gh-107704: Argument Clinic: support multiple '/ [from ...]' and '* [from ...]' markers #108132