Add `String::replace_first` and `String::replace_last` #134316

zachs18 · 2024-12-14T21:15:39Z

Convenience methods that use match_indices and replace_range to efficiently replace a substring in a string without reallocating, if capacity (and the implementation of Vec::splice) allows.

The intra-doc link to str::replacen is a direct url-based link to str::replacen in std's docs to work around #98941. This means that when building only alloc's docs (and not std's), it will be a broken link. There is precedent for this e.g. in core::hint::spin_loop which links to std::thread::yield_now using a url-based link and thus is a dead link when only building core's docs.

ACP: rust-lang/libs-team#506

rustbot · 2024-12-14T21:15:48Z

r? @tgross35

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tgross35 · 2024-12-14T21:20:56Z

I don't think I see any libs-api feedback on the other thread, and that is from a while back anyway. Could you file an ACP for this at https://github.com/rust-lang/libs-team/issues?

tgross35 · 2024-12-14T21:44:56Z

These methods would be convenient but I feel like they should probably come with an in-place replace alternative.

zachs18 · 2024-12-15T03:00:43Z

ACP opened: rust-lang/libs-team#506

@rustbot label S-waiting-on-ACP

I added String::replace_in_place (doing str::replace in-place) as a possible alternative/addition in the ACP, but I'll hold off on adding it if/until the ACP is approved with it.

bors · 2025-01-09T19:53:23Z

☔ The latest upstream changes (presumably #135286) made this pull request unmergeable. Please resolve the merge conflicts.

alex-semenyuk · 2025-02-21T20:21:01Z

@zachs18
Thanks for your contribution
Could you please rebase

tgross35 · 2025-02-21T20:23:06Z

@zachs18 Thanks for your contribution Could you please rebase

This is still waiting on the ACP

joshtriplett · 2025-10-21T15:19:44Z

@bors r+ rollup

ACP approved, PR approved.

Might be interested in the proposed replace_in_place in the future, but these seem clearly valuable and worth adding.

bors · 2025-10-21T15:19:48Z

📌 Commit 0243f5c has been approved by joshtriplett

It is now in the queue for this repository.

joshtriplett · 2025-10-21T15:20:03Z

@bors r-

r=me when the conflicts are fixed.

library/alloc/src/string.rs

tgross35 · 2025-10-21T20:30:07Z

Please also squash when you rebase, this PR has fixup commits

Rebased and modified by zachs18. Co-authored-by: zachs18 <[email protected]>

rustbot · 2025-10-21T21:14:19Z

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

zachs18 · 2025-10-21T21:23:51Z

@rustbot ready

tgross35 · 2025-10-21T21:35:05Z

library/alloc/src/lib.rs

 //
 // Library features:
 // tidy-alphabetical-start
+#![cfg_attr(not(no_global_oom_handling), feature(string_replace_in_place))]


Fwiw I think you may as well drop the cfg_attr and enable the feature unconditionally, usually we don't gate these too strictly. And we'll wind up using it elsewhere anyway.

I'll merge after PR CI finishes, with or without this (just ping me once it does if I miss it)

This might actually be needed (?), since its absence seems to be what the failed CI job is complaining about.

Yeah; I'm sorry, this was bad advice.

I undid this (that is, undid removing cfg_attr, so re-added it) and re-pushed

@rustbot ready

tgross35 · 2025-10-22T17:59:40Z

Thanks! I assume the GCC failure is spurious

@bors r=joshtriplett ,tgross35

bors · 2025-10-22T17:59:43Z

📌 Commit 271b10c has been approved by joshtriplett

It is now in the queue for this repository.

tgross35 · 2025-10-22T17:59:48Z

@bors rollup

…base, r=joshtriplett Add `String::replace_first` and `String::replace_last` Rebase of rust-lang#97977 (cc `@WilliamVenner)` > Convenience methods that use `match_indices` and `replace_range` to efficiently replace a substring in a string without reallocating, if capacity (and the implementation of `Vec::splice`) allows. The intra-doc link to `str::replacen` is a direct url-based link to `str::replacen` in `std`'s docs to work around rust-lang#98941. This means that when building only `alloc`'s docs (and not `std`'s), it will be a broken link. There is precedent for this e.g. in [`core::hint::spin_loop`](https://doc.rust-lang.org/nightly/src/core/hint.rs.html#214) which links to `std::thread::yield_now` using a [url-based link](https://github.com/rust-lang/rust/blob/master/library/core/src/hint.rs#L265) and thus is a dead link when only building `core`'s docs. ACP: rust-lang/libs-team#506

Zalathar · 2025-10-23T01:04:44Z

The GCC job failed again in rollup: #148010 (comment)

@bors r-

tgross35 · 2025-10-23T05:08:10Z

@bors r=joshtriplett ,tgross35

bors · 2025-10-23T05:08:12Z

📌 Commit 8ed7fca has been approved by joshtriplett

It is now in the queue for this repository.

Rollup of 3 pull requests Successful merges: - #134316 (Add `String::replace_first` and `String::replace_last`) - #147713 (Retire ast::TyAliasWhereClauses.) - #148011 (Revert constification of `AsRef for Cow` due to inference failure ) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #134316 - zachs18:string_replace_in_place_rebase, r=joshtriplett Add `String::replace_first` and `String::replace_last` Rebase of #97977 (cc `@WilliamVenner)` > Convenience methods that use `match_indices` and `replace_range` to efficiently replace a substring in a string without reallocating, if capacity (and the implementation of `Vec::splice`) allows. The intra-doc link to `str::replacen` is a direct url-based link to `str::replacen` in `std`'s docs to work around #98941. This means that when building only `alloc`'s docs (and not `std`'s), it will be a broken link. There is precedent for this e.g. in [`core::hint::spin_loop`](https://doc.rust-lang.org/nightly/src/core/hint.rs.html#214) which links to `std::thread::yield_now` using a [url-based link](https://github.com/rust-lang/rust/blob/master/library/core/src/hint.rs#L265) and thus is a dead link when only building `core`'s docs. ACP: rust-lang/libs-team#506

Rollup of 3 pull requests Successful merges: - rust-lang/rust#134316 (Add `String::replace_first` and `String::replace_last`) - rust-lang/rust#147713 (Retire ast::TyAliasWhereClauses.) - rust-lang/rust#148011 (Revert constification of `AsRef for Cow` due to inference failure ) r? `@ghost` `@rustbot` modify labels: rollup

rustbot assigned tgross35 Dec 14, 2024

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zachs18 mentioned this pull request Dec 15, 2024

In-place String::replace_first and String::replace_last rust-lang/libs-team#506

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zachs18 mentioned this pull request Oct 21, 2025

Tracking Issue for string_replace_in_place #147949

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Add String::replace_first and String::replace_last

8ed7fca

Rebased and modified by zachs18. Co-authored-by: zachs18 <[email protected]>

zachs18 force-pushed the string_replace_in_place_rebase branch from 0243f5c to 8ed7fca Compare October 21, 2025 21:14

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tgross35 approved these changes Oct 21, 2025

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zachs18 force-pushed the string_replace_in_place_rebase branch from 8ed7fca to 271b10c Compare October 22, 2025 17:00

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Zalathar mentioned this pull request Oct 22, 2025

Rollup of 5 pull requests #148010

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bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Oct 23, 2025

zachs18 force-pushed the string_replace_in_place_rebase branch from 271b10c to 8ed7fca Compare October 23, 2025 03:37

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Rollup of 3 pull requests #148014

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bors merged commit 4491efb into rust-lang:master Oct 23, 2025
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Add String::replace_first and String::replace_last #134316

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Add `String::replace_first` and `String::replace_last` #134316

Add `String::replace_first` and `String::replace_last` #134316

zachs18 commented Dec 14, 2024 •

edited by Dylan-DPC

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