Soft deprecate `re.match` and `re.Pattern.match` in favour of `prefixmatch`

[hugovk]

Feature or enhancement

Proposal:

In #86519 (PR #31137), we added new re.prefixmatch and re.Pattern.prefixmatch as explicit names for re.match and re.Pattern.match, because it's really not obvious the shorter old names include a prefix anchor; you probably meant to use search (no anchors) or fullmatch (prefix and suffix anchors).

This is essentially a soft deprecation of the match names:

• It's okay to use the old name in old code, but prefer the new name in new code.
• We don't plan on removing the old name or emitting deprecation warnings.

Let's make this explicit.

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-148100: Soft deprecate re.match and re.Pattern.match in favour of prefixmatch #148101

[serhiy-storchaka]

My objection to prefixmath was exactly this -- that it will lead to deprecation of match. Even if it is initially a soft-deprecation, it will cause a tsunami of PRs in Python and other projects to replace match with prefixmath. This in unnecessary code churn that will affect each Python project.

I was told that this would never happen. And here it is.

[hugovk]

This is absolutely and explicitly not a regular "hard" deprecation.

A soft deprecation is clearly defined:

• Something which you should not use in new code.
• Safe for existing code.
• No deprecation warnings.

It's only in docs, which clearly says we do not plan to remove it.

#31137 was a soft deprecation; this is labelling it as such.

I completely agree that match too widespread to "hard" deprecate.

I don't think there'll be a tsunami of PRs, but I hope people take another look at their uses of match and consider if they should be search or fullmatch instead.

The first codebase I just searched has a match that should really be fullmatch. And for 3.15+ projects (many won't be for another five years), I do think explicit prefixmatch is clearer than match. But labelling this a soft deprecation doesn't change any of this.

[serhiy-storchaka]

How do you stop other people from creating PRs to replace match with prefixmatch? This is a low hanging fruit, we will get such PRs every few months, and finally some of them will slip past the watchdog. How do you stop this in other projects, not only in open source projects on GitHub? How do you stop linters to add a rule to recommend prefixmatch over match? And now it is easy to create LLM generated PRs to hundreds of projects.

Do you think all those man-hours spent globally reviewing and discussing such changes are worth it? On a global scale, it could be man-years.