feat(profile): Add built-in profile debug by epage · Pull Request #17214 · rust-lang/cargo

epage · 2026-07-14T20:18:10Z

What does this PR try to resolve?

Key points:

It inherits from dev
- Conceptually, debugging is part of the development process
- The hope is this will smooth out the transition for people
cargo install --debug now uses debug instead of dev
debug changes nothing from dev right now.
dev will evolve in the future
(with debug overriding those values to leave it effectively unchanged)
but that is deferred out to offer a transition period where debug
can be used without but isn't required for debugging as people deal
with multiple Rust versions. This also shrinks the change and
decouples what the conversation around what the settings should be.
dev still uses target/debug: this does not change any calculation for the transition cost and any conflicts between the profiles should mostly be in the artifact-dir (which are just hard links), especially once the new build layout lands
--dev/--debug flags are deferred out, needing more evaluation to decide if they are worth it

See also https://github.com/rust-lang/cargo-team/blob/main/meetings/sync-meeting/2026-07-14.md#splitting-dev-and-debug-profiles

How to test and review this PR?

This is part of #15931

build.profile will be a follow up (feat(config): Add build.profile, install.profile #17215)
dev profile changes are deferred for 1+ releases

rustbot · 2026-07-14T20:18:15Z

r? @ehuss

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Owners of files modified in this PR: @ehuss, @epage, @weihanglo
@ehuss, @epage, @weihanglo expanded to ehuss, epage, weihanglo
Random selection from ehuss, weihanglo

weihanglo · 2026-07-16T14:30:09Z

Should we include the meeting note in the PR description?
https://github.com/rust-lang/cargo-team/blob/main/meetings/sync-meeting/2026-07-14.md#splitting-dev-and-debug-profiles

epage · 2026-07-17T01:06:51Z

Added the link and what looked like I might have been missing

weihanglo

I think this is less risky as debug has been a reserved profile for a long while, and people kinda agree on the direction in the meeting this week, so probably don't need an FCP. What do you think?

View changes since this review

weihanglo · 2026-07-17T13:37:11Z

@rfcbot fcp merge T-cargo

This is a one-way-door decision that debug becomes an actual profile. See the PR description for details.

rust-rfcbot · 2026-07-17T13:37:31Z

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

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.

epage · 2026-07-17T13:40:57Z

While we can pivot, I think an FCP is important as this is setting a direction and can be disruptive to the ecosystem if we pivoted on that direction.

rust-rfcbot · 2026-07-28T21:11:31Z

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

0xPoe

Thanks!
Do we need to update the help text as well?

cargo/src/bin/cargo/commands/install.rs

Line 97 in 88c5c58

"Build in debug mode (with the 'dev' profile) instead of release mode",

And do we need to update default_profile_candidates to include the debug profile?

And for build cache docs, as you mentioned it in your PR body, I’m not sure it’s worth mentioning the debug profile in it.

View changes since this review

Key points: - It inherits from `dev` - Conceptually, debugging is part of the development process - The hope is this will smooth out the transition for people - `cargo install --debug` now uses `debug` instead of `dev` - `debug` changes nothing from `dev` right now. `dev` will evolve in the future (with `debug` overriding those values to leave it effectively unchanged) but that is deferred out to offer a transition period where `debug` can be used without but isn't required for debugging as people deal with multiple Rust versions. This also shrinks the change and decouples what the conversation around what the settings should be.

rustbot · 2026-07-31T16:55:02Z

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.

rust-rfcbot · 2026-08-07T21:12:07Z

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.

weihanglo · 2026-08-07T21:51:13Z

Let's merge it. We have lots of things today!

Update cargo submodule 14 commits in c79e8f89441b3e73d6d65d125c0c745792808c74..b07e5a08651da80108eb65d7dc769ee04589f9bf 2026-08-04 19:17:33 +0000 to 2026-08-07 21:51:16 +0000 - feat(profile): Add built-in profile debug (rust-lang/cargo#17214) - feat(toml): allow overriding inherited default-features in 2024 (rust-lang/cargo#17126) - feat(resolver): Report the min-publish-age in the lock message (rust-lang/cargo#17328) - refactor(resolver): resolve() does not need an optional gctx (rust-lang/cargo#17331) - fix(resolver): Make min-publish-age relative to --publish-time (rust-lang/cargo#17327) - test(trim-paths): exercise unremap files with debuggers (rust-lang/cargo#17326) - feat(log): emit build-started JSON message with run_id (rust-lang/cargo#16632) - docs: remove stray `directory` metavar from `cargo update --breaking` option (rust-lang/cargo#17319) - fix(lock): Use more accurate 'highest, rather than 'latest' (rust-lang/cargo#17317) - docs(changelog): Pull the --verbose item (rust-lang/cargo#17315) - revert(compiler): forward verbose flag to rustc for local crates (rust-lang/cargo#17314) - fix(diag): Gate blanket_hint_mostly_unused with -Zprofile-hint-mostly-unused (rust-lang/cargo#17313) - fix(diag): Remove complexity, perf, and nursery lint groups (rust-lang/cargo#17307) - fix(git): Avoid use of git's core.fsmonitor (rust-lang/cargo#17306) r? ghost

rustbot assigned ehuss Jul 14, 2026

rustbot added the A-cli Area: Command-line interface, option parsing, etc. label Jul 14, 2026

epage marked this pull request as draft July 14, 2026 20:18

rustbot added the A-cli-help Area: built-in command-line help label Jul 14, 2026

epage mentioned this pull request Jul 14, 2026

feat(config): Add build.profile, install.profile #17215

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epage force-pushed the debug-profile branch from 59d0706 to 0c186d2 Compare July 15, 2026 00:10

epage marked this pull request as ready for review July 15, 2026 00:10

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 15, 2026

epage force-pushed the debug-profile branch from 0c186d2 to f2305ae Compare July 16, 2026 14:08

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weihanglo approved these changes Jul 17, 2026

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weihanglo added the T-cargo Team: Cargo label Jul 17, 2026

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rust-rfcbot added proposed-final-comment-period An FCP proposal has started, but not yet signed off. disposition-merge FCP with intent to merge labels Jul 17, 2026

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test(profile): Pull out debug test

ba0a60c

epage force-pushed the debug-profile branch from f2305ae to 88c5c58 Compare July 17, 2026 21:04

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ehuss added this to Cargo status tracker Jul 21, 2026

ehuss moved this to FCP merge in Cargo status tracker Jul 21, 2026

rust-rfcbot added final-comment-period FCP — a period for last comments before action is taken and removed proposed-final-comment-period An FCP proposal has started, but not yet signed off. labels Jul 28, 2026

0xPoe reviewed Jul 30, 2026

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Comment thread doc/book/src/commands/cargo-test.md Outdated

Comment thread tests/testsuite/profile_custom.rs Outdated

epage added 3 commits July 31, 2026 11:47

test(profile): Fix assert conditions

825f7c3

test(profile): Expand debug profile coverage

0cc4686

epage force-pushed the debug-profile branch from 88c5c58 to 677f7bb Compare July 31, 2026 16:54

rustbot added the Command-install label Jul 31, 2026

epage force-pushed the debug-profile branch from 677f7bb to c916d36 Compare July 31, 2026 16:55

rust-rfcbot added finished-final-comment-period FCP complete and removed final-comment-period FCP — a period for last comments before action is taken labels Aug 7, 2026

rust-rfcbot added the to-announce label Aug 7, 2026

weihanglo added this pull request to the merge queue Aug 7, 2026

Merged via the queue into rust-lang:master with commit b07e5a0 Aug 7, 2026
29 checks passed

rustbot removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Aug 7, 2026

weihanglo mentioned this pull request Aug 7, 2026

Update cargo submodule rust-lang/rust#160727

Merged

rustbot added this to the 1.99.0 milestone Aug 8, 2026

epage deleted the debug-profile branch August 10, 2026 17:06

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