Don't panic in <BorrowedCursor as io::Write>::write

[zachs18]

Instead of panicking if the BorrowedCursor does not have enough capacity for the whole buffer, just return a short write, like <&mut [u8] as io::Write>::write does.

(cc @ChayimFriedman2 #78485 (comment))

(I'm not sure if this needs an ACP? since it's not changing the "API", just what the function does)

[rustbot]

r? @thomcc

(rustbot has picked a reviewer for you, use r? to override)

[djc]

This makes sense to me!

[djc]

@thomcc gentle ping? Should this get another reviewer?

[joboet]

I'm going to take the liberty of assigning this to someone from libs-api since this is technically a user-facing change, even if it merely fixes a bug.

r? libs-api
@rustbot label +T-libs-api

[Amanieu]

This is a very minor API change, but ultimately I think the new behavior is better than the old one. It is also consistent with other Write implementations.

@rfcbot fcp merge

[rfcbot]

Team member @Amanieu has proposed to merge this. The next step is review by the rest of the tagged team members:

• @Amanieu
• @BurntSushi
• @cuviper
• @dtolnay
• @joshtriplett
• @m-ou-se
• @the8472
• @thomcc

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.

[thomcc]

Should libs be on this FCP?

[Amanieu]

Hmm probably not but at this point I don't think it really hurts.

[the8472]

BorrowedCursor is unstable anyway and write_all turns this into an Errorkind::WriteZero. Seems fine.

[rfcbot]

🔔 This is now entering its final comment period, as per the review above. 🔔

[rfcbot]

The final comment period, with a disposition to merge, as per the review above, is now complete.

As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed.

This will be merged soon.

[dtolnay]

@bors r+

[bors]

📌 Commit 11a64a1 has been approved by dtolnay

It is now in the queue for this repository.

[bors]

⌛ Testing commit 11a64a1 with merge 28acba3...

[bors]

☀️ Test successful - checks-actions
Approved by: dtolnay
Pushing 28acba3 to master...

[rust-timer]

Finished benchmarking commit (28acba3): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.9%	[0.5%, 1.4%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.7%	[-0.9%, -0.4%]	4
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.1%	[-0.9%, 1.4%]	6

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 663.194s -> 662.725s (-0.07%)
Artifact size: 308.72 MiB -> 308.73 MiB (0.00%)