feat(toml): allow overriding inherited default-features in 2024 by 0xPoe · Pull Request #17126 · rust-lang/cargo

0xPoe · 2026-06-21T22:15:37Z

What does this PR try to resolve?

Implement RFC 3945, on Edition 2024+ allow workspace members to override the workspace dependency's default-features setting.

Earlier editions are unchanged: setting default-features on an inherited dependency is still ignored with a warning.

Also, this change would allow cargo add X --no-default-features -p Y, but only on Edition 2024+.

How to test and review this PR?

Review and check it commit by commit.

r?@ghost

Impl RFC 3945, on Edition 2024+ allow workspace members to override the workspace dependency's `default-features` setting. Earlier editions are unchanged: setting `default-features` on an inherited dependency is still ignored with a warning. Signed-off-by: 0xPoe <techregister@pm.me>

Signed-off-by: 0xPoe <techregister@pm.me>

0xPoe

cargo add dep --default-features -p app doesn't work correctly. I will rework this.

View changes since this review

epage · 2026-06-23T22:38:56Z

Will we need to update https://doc.rust-lang.org/edition-guide/rust-2024/cargo-inherited-default-features.html as part of this?

`cargo add --no-default-features` (or `--default-features`) against a dependency inherited from `[workspace.dependencies]` is now allowed when the package is on Edition 2024+, matching the manifest behavior. Earlier editions still error, pointing the user to the workspace manifest. Signed-off-by: 0xPoe <techregister@pm.me>

Signed-off-by: 0xPoe <techregister@pm.me>

0xPoe · 2026-06-24T22:11:17Z

Will we need to update doc.rust-lang.org/edition-guide/rust-2024/cargo-inherited-default-features.html as part of this?

Yes, I will create a PR for this.

0xPoe

🔢 Self-check (PR reviewed by myself and ready for feedback)

Code compiles successfully
Unit tests added
No AI-generated elegant nonsense in PR.
Comments added where necessary
PR title and description updated
Documentation updated
PR size is reasonable

View changes since this review

0xPoe · 2026-06-24T22:31:16Z

+- [`default-features`][default-features] (Edition 2024 packages, requires Rust 1.98+):
+  Overrides the value set in `[workspace.dependencies]`.
+  If neither the package nor the workspace specifies `default-features`, it defaults to `true`.
+  Before Rust 1.98, or in earlier editions, package-level `default-features = false`


Not sure if this is the perfect word for it, and not sure how detailed we should be here.

epage · 2026-06-30T01:58:20Z

                false,
                None,
-                true,
+                None,


Do we have a test case for

$ cargo init $ cargo add foo --default-features

ie explicit --default-features with the foo = "1.0" case

View changes since the review

No, we don’t have a case that compiles with cargo init, especially with edition 2024. So I added a new one.

Added in 62a3dd8 (this PR)

Just dropped it, as I had a conversation with @epage offline. He didn’t mean to literally have cargo init here, but to start with a fresh Cargo.toml. A test would exist to make sure --default-features doesn’t set default-features = true when it isn’t needed, as tests/testsuite/cargo_add/default_features already covered this. So I dropped my last commit.

Signed-off-by: 0xPoe <techregister@pm.me>

epage · 2026-07-14T15:58:16Z

@rfcbot fcp merge cargo

This implements RFC 3945 which takes an error case in the 2024 edition and makes it a success case.

rust-rfcbot · 2026-07-14T15:58:19Z

@epage 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.

0xPoe · 2026-07-14T19:46:40Z

Nothing changed, just dropped an unnecessary test commit. See: #17126 (comment)

rustbot · 2026-07-17T18:02:43Z

☔ The latest upstream changes (possibly #17230) made this pull request unmergeable. Please resolve the merge conflicts.

rustbot added A-documenting-cargo-itself Area: Cargo's documentation A-manifest Area: Cargo.toml issues Command-add labels Jun 21, 2026

0xPoe force-pushed the poe-patch-inherit-default-features branch from c1ee481 to a6548d4 Compare June 23, 2026 21:19

0xPoe force-pushed the poe-patch-inherit-default-features branch from a6548d4 to 72f4119 Compare June 23, 2026 21:28

test(add): add inherit no default features case

8f80a48

Signed-off-by: 0xPoe <techregister@pm.me>

0xPoe force-pushed the poe-patch-inherit-default-features branch from 72f4119 to 62db596 Compare June 23, 2026 21:34

0xPoe marked this pull request as ready for review June 23, 2026 21:34

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 23, 2026

0xPoe changed the title ~~NOT READY FOR REVIEW: feat(toml): allow overriding inherited default-features in 2024~~ feat(toml): allow overriding inherited default-features in 2024 Jun 23, 2026

0xPoe commented Jun 23, 2026

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rustbot assigned weihanglo Jun 23, 2026

0xPoe marked this pull request as draft June 23, 2026 22:02

rustbot removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 23, 2026

0xPoe changed the title ~~feat(toml): allow overriding inherited default-features in 2024~~ WIP: feat(toml): allow overriding inherited default-features in 2024 Jun 23, 2026

epage approved these changes Jun 23, 2026

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Comment thread src/cargo/util/toml/mod.rs Outdated

Comment thread src/doc/src/reference/workspaces.md Outdated

0xPoe added 3 commits June 24, 2026 23:51

test(add): add inherit default features case

b4908af

Signed-off-by: 0xPoe <techregister@pm.me>

fix(add): set dep's default features explicitly

42a33c6

Signed-off-by: 0xPoe <techregister@pm.me>

0xPoe force-pushed the poe-patch-inherit-default-features branch 3 times, most recently from f2f677f to 17595ac Compare June 24, 2026 22:04

0xPoe marked this pull request as ready for review June 24, 2026 22:11

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 24, 2026

0xPoe changed the title ~~WIP: feat(toml): allow overriding inherited default-features in 2024~~ feat(toml): allow overriding inherited default-features in 2024 Jun 24, 2026

0xPoe force-pushed the poe-patch-inherit-default-features branch 2 times, most recently from 33ca750 to 1b14f50 Compare June 24, 2026 22:32

0xPoe commented Jun 24, 2026

View reviewed changes

0xPoe requested a review from epage June 25, 2026 13:56

epage reviewed Jun 30, 2026

View reviewed changes

Comment thread src/cargo/util/toml/mod.rs Outdated

0xPoe force-pushed the poe-patch-inherit-default-features branch from e97fffa to 62a3dd8 Compare June 30, 2026 19:24

0xPoe requested a review from epage July 1, 2026 20:53

0xPoe added 2 commits July 12, 2026 23:26

fix(add): update outdated warnings

88eb1ad

Signed-off-by: 0xPoe <techregister@pm.me>

docs: document overriding inherited default-features

c4ed736

Signed-off-by: 0xPoe <techregister@pm.me>

0xPoe force-pushed the poe-patch-inherit-default-features branch from 62a3dd8 to 0cf7b7e Compare July 12, 2026 21:27

epage added the T-cargo Team: Cargo label Jul 14, 2026

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 14, 2026

0xPoe force-pushed the poe-patch-inherit-default-features branch from 0cf7b7e to c4ed736 Compare July 14, 2026 19:44

ehuss added this to Cargo status tracker Jul 21, 2026

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

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