[issue31742] Default to emitting FutureWarning for provisional APIs

[Guido van Rossum]

Guido van Rossum <guido at python.org> added the comment:

I'm still trying to understand whether there's a specific event (or set of events) that's triggered this issue. There is a lot of talk about people can be misled but not a single specific example of someone who actually got in trouble because a provisional API they were actually using changed.

Given the passion I read in some of the comments it shouldn't be hard to collect such stories?

As with every other change proposed to Python, unless there's a clear indication that there is an actual problem, I'm not inclined to try to solve it preemptively (since the proposed action also may *introduce* new problems). Note that I'm not asking for proof that some people don't know what provisional means -- I'm looking for evidence of actual situations where someone got bitten.

Also I don't think that people who didn't read the docs have much of a leg to stand on. There are plenty of situations where subtle aspects of APIs are not guaranteed to be stable (e.g. calling a function with a value that the docs say is invalid but that is not actively rejected by some version). And nobody can expect that a talk (no matter how clearly presented) is a substitute for reading the docs -- a talk on a complex API like asyncio or typing cannot possibly cover the whole API (I know, I've tried :-).

That said, we should absolutely change the warnings in the docs.

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue31742>
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