gh-127371 Avoid unbounded growth SpooledTempfile.writelines

[bertptrs]

By checking after every line whether we've rolled over, we ensure that internal buffer doesn't grow too far beyond the expected bounds (at most one line).

To avoid a performance regression, I opted to introduce several fast-paths: if the SpooledTemplFile has already been rolled over to disk, or if it never will because the size is unbounded, the implementation delegates directly to the underlying file object.

• Issue: Unbounded growth in SpooledTemporaryFile.writelines() #127371

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[tomasr8]

Thanks! I think this also needs a test :)

[bertptrs]

Thanks for the review! Addressed your comments and added a simple test.

[tomasr8]

Thanks! Please avoid force pushing if possible, it makes it more difficult to see what the latest changes are 🙂

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[bertptrs]

I think it should be good like this, then. Note: I'm aware of the failing CI test for my news entry, but I don't know what's wrong about the way I linked the method. Could you help me with that?

[tomasr8]

I think it should be good like this, then. Note: I'm aware of the failing CI test for my news entry, but I don't know what's wrong about the way I linked the method. Could you help me with that?

I think that's because the method is not documented so there is nothing to link to. IIRC ! should fix it, i.e.:

:meth:`!tempfile.SpooledTemporaryFile.writelines`

[tomasr8]

LGTM! :)