fix(path): clarify error message when path dependency has wrong package by raushan728 · Pull Request #16927 · rust-lang/cargo

raushan728 · 2026-04-22T10:39:39Z

When a path dependency points to a directory with a wrong or missing package, Cargo now scans subdirectories and shows helpful hints about what packages exist nearby.

rustbot · 2026-04-22T10:39:44Z

r? @epage

rustbot has assigned @epage.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

Why was this reviewer chosen?

The reviewer was selected based on:

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

epage

Thanks!

View changes since this review

raushan728 · 2026-04-30T07:08:10Z

Since PathSource::query() now returns zero candidates for missing Cargo.toml instead of an IO error, some existing tests that expected the old error chain now show the resolver-level error message instead.

epage · 2026-05-11T14:32:45Z

-            ))),
+            None => {
+                let path = self.path.join("Cargo.toml");
+                ops::read_package(&path, self.source_id, self.gctx)?;


Why are we doing a read_package here?

View changes since the review

root_package() is called when Cargo.toml is missing but we still need the original IO error to propagate. Since read_package() now returns Ok(None) for missing files, we call ops::read_package directly to get the proper error.

Why do we need the original IO error?

The uninstall_cwd_no_project test expects the original "failed to read Cargo.toml" IO error when running cargo uninstall in a directory without a Cargo.toml. Without this call, root_package() would return the internal "no package found in source" error instead, which is a regression in the error message for users running cargo commands outside of a project directory.

root_package basically exists for cargo install / cargo uninstall. If I'm understanding correctly, we'd fallback to the error no package found in source. What if we replaced that text with failed to read {} in its own commit before this?

Sorry for pushing without confirmation went with Option<Option<Package>> approach as it felt the cleanest of the three options.

Note my "if". What I would expect is some discussion as to why we think keeping the internal error is important before moving forward, or at least when pushing the changes.

I would recommend communicating more as you contribute. For example, there have been several times where you've made decisions along the way and had the context for them but didn't post that with the PR update, requiring extra rounds of back and forth as I then need to get that context that wasn't included.

Went with Option<Option<>> as it was the simplest no new types needed, cleanly separates unloaded, missing, and loaded states.

For the "if" root_package is used by cargo uninstall outside a project, so some error is needed there. Used anyhow::format_err! instead of internal since a missing Cargo.toml is a user error not a Cargo bug, which avoids the bug report notes. Dropped Caused by: NOT_FOUND as you suggested.

Will post reasoning with each update going forward.

@epage I know you're busy no rush. I'm a student learning open source contribution and want to make sure this PR moves forward. Happy to make any changes you suggest. Please let me know when you get a chance.

Also, English is not my first language and I sometimes miss the nuance in your comments, which has led to some misunderstandings. I appreciate your patience and will try to ask for clarification before making changes.

Track missing Cargo.toml state using Option<Option<Package>>, where outer None means unloaded and inner None means loaded but missing. This allows the resolver to produce standard diagnostics instead of raw IO error chains.

- Scan subdirectories when a path dependency is missing or invalid. - Show helpful hints suggesting packages that exist nearby. Fixes rust-lang#15296

rustbot · 2026-05-22T15:57:42Z

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.

rustbot added A-dependency-resolution Area: dependency resolution and the resolver S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Apr 22, 2026

rustbot assigned epage Apr 22, 2026

epage reviewed Apr 22, 2026

View reviewed changes

raushan728 force-pushed the fix-15296 branch from 1978dbb to bacfa17 Compare April 23, 2026 11:34

rustbot added the A-registries Area: registries label Apr 23, 2026

This comment has been minimized.

Sign in to view

raushan728 requested a review from epage April 23, 2026 12:47

epage reviewed Apr 23, 2026

View reviewed changes

Comment thread src/cargo/core/resolver/errors.rs

epage reviewed Apr 23, 2026

View reviewed changes

Comment thread src/cargo/core/resolver/errors.rs Outdated

epage reviewed Apr 23, 2026

View reviewed changes

Comment thread src/cargo/core/resolver/errors.rs Outdated

epage reviewed Apr 23, 2026

View reviewed changes

Comment thread src/cargo/core/registry.rs Outdated

raushan728 force-pushed the fix-15296 branch 3 times, most recently from d5f8d89 to 603d687 Compare April 24, 2026 06:58

This comment was marked as duplicate.

Sign in to view

raushan728 requested a review from epage April 26, 2026 14:48

epage reviewed Apr 27, 2026

View reviewed changes

Comment thread src/cargo/core/resolver/errors.rs

epage reviewed Apr 27, 2026

View reviewed changes

Comment thread src/cargo/core/resolver/errors.rs Outdated

raushan728 force-pushed the fix-15296 branch from 603d687 to 744492b Compare April 30, 2026 07:05

This comment has been minimized.

Sign in to view

raushan728 force-pushed the fix-15296 branch 2 times, most recently from 94076b6 to fb20a60 Compare May 1, 2026 08:54

raushan728 requested a review from epage May 1, 2026 09:20

raushan728 force-pushed the fix-15296 branch from fb20a60 to 0d5ca85 Compare May 5, 2026 09:35

This comment has been minimized.

Sign in to view

epage reviewed May 10, 2026

View reviewed changes

Comment thread src/cargo/sources/path.rs Outdated

epage reviewed May 10, 2026

View reviewed changes

Comment thread src/cargo/sources/path.rs

epage reviewed May 10, 2026

View reviewed changes

Comment thread tests/testsuite/path.rs

epage reviewed May 10, 2026

View reviewed changes

Comment thread tests/testsuite/path.rs

epage reviewed May 10, 2026

View reviewed changes

Comment thread src/cargo/core/resolver/errors.rs Outdated

raushan728 force-pushed the fix-15296 branch from 0d5ca85 to 87ed57e Compare May 10, 2026 11:05

This comment has been minimized.

Sign in to view

raushan728 requested a review from epage May 10, 2026 11:29

epage reviewed May 11, 2026

View reviewed changes

raushan728 force-pushed the fix-15296 branch from 87ed57e to 87b114b Compare May 12, 2026 05:38

This comment has been minimized.

Sign in to view

raushan728 force-pushed the fix-15296 branch 2 times, most recently from 142213e to 2fb9cd0 Compare May 12, 2026 06:53

raushan728 requested a review from epage May 12, 2026 07:23

raushan728 force-pushed the fix-15296 branch from 2fb9cd0 to a9df55a Compare May 14, 2026 08:16

This comment has been minimized.

Sign in to view

raushan728 closed this May 14, 2026

rustbot removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label May 14, 2026

raushan728 reopened this May 14, 2026

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label May 14, 2026

raushan728 added 3 commits May 17, 2026 05:49

test(path): add tests for path dependency wrong package error message

4035e31

fix(path): handle missing Cargo.toml gracefully in PathSource

d78868d

Track missing Cargo.toml state using Option<Option<Package>>, where outer None means unloaded and inner None means loaded but missing. This allows the resolver to produce standard diagnostics instead of raw IO error chains.

fix(path): suggest nearby packages for invalid path dependencies

21fa9b6

- Scan subdirectories when a path dependency is missing or invalid. - Show helpful hints suggesting packages that exist nearby. Fixes rust-lang#15296

raushan728 force-pushed the fix-15296 branch from a9df55a to 21fa9b6 Compare May 22, 2026 15:57

Conversation

raushan728 commented Apr 22, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

rustbot commented Apr 22, 2026

Uh oh!

epage left a comment • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

This comment has been minimized.

Uh oh!

Uh oh!

Uh oh!

Uh oh!

This comment was marked as duplicate.

Uh oh!

Uh oh!

This comment has been minimized.

raushan728 commented Apr 30, 2026

Uh oh!

This comment has been minimized.

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

This comment has been minimized.

epage May 11, 2026 • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

raushan728 May 12, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

epage May 12, 2026

Choose a reason for hiding this comment

Uh oh!

raushan728 May 12, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

epage May 12, 2026

Choose a reason for hiding this comment

Uh oh!

raushan728 May 14, 2026

Choose a reason for hiding this comment

Uh oh!

epage May 14, 2026

Choose a reason for hiding this comment

Uh oh!

raushan728 May 15, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

raushan728 May 24, 2026

Choose a reason for hiding this comment

Uh oh!

raushan728 May 24, 2026

Choose a reason for hiding this comment

Uh oh!

This comment has been minimized.

This comment has been minimized.

rustbot commented May 22, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

raushan728 commented Apr 22, 2026 •

edited

Loading

epage left a comment •

edited by rustbot

Loading

epage May 11, 2026 •

edited by rustbot

Loading

raushan728 May 12, 2026 •

edited

Loading

raushan728 May 12, 2026 •

edited

Loading

raushan728 May 15, 2026 •

edited

Loading