Validate target source paths before compilation with clearer errors #16338

TanmayArya-1p · 2025-12-04T09:40:25Z

What does this PR try to resolve?

This PR adds early validation of target source paths with clearer error messages.

For context, I tried to solve this issue before ( #16329 ) but ended up making an oversight, I would recommend reading this to understand the issues faced in resolving this.

So what changed in this PR?

Root Target Units are validated early on in the compilation pipeline when the BuildContext is generated here. This is right after command line arguments/manifest targets are parsed and just before the build tasks are spawned.
Cases that are covered by this PR:
- If the target path is invalid and points to nothing.
- If the target path is valid, but is a directory (not a file)
- If the target path is a valid directory with a main.rs/lib.rs depending on the Target kind: In this case a help: message is emitted.

Doing this also means that Cargo validates each root target's path that is requested to be compiled before spawning any build tasks.
This PR enforces the invariant: No compilation occurs before validating every required target's source path.
I'm not sure if this should be expected behaviour and I'd love to hear from others on this.

rustbot · 2025-12-04T10:20:52Z

r? @epage

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tests/testsuite/bad_config.rs

src/cargo/util/targets.rs

tests/testsuite/bad_config.rs

epage · 2025-12-05T01:30:49Z

Feel free to edit your commits for how they should be merged.

src/cargo/ops/cargo_compile/mod.rs

rustbot · 2025-12-05T04:12:44Z

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.

TanmayArya-1p · 2025-12-05T05:00:51Z

Thanks for the review!
I fixed the issues you pointed out, Let me know if it needs to be changed.

Also could you rerun the CI workflow because it failed with this error:

https://github.com/rust-lang/cargo/actions/runs/19952419092/job/57215065207#annotation:2:61

Error: fatal: unable to access 'https://github.com/rust-lang/cargo/': Failed to connect to github.com port 443 after 21029 ms: Could not connect to server
Error: The process 'C:\Program Files\Git\bin\git.exe' failed with exit code 128

epage · 2025-12-05T14:46:46Z

I fixed the issues you pointed out, Let me know if it needs to be changed.

FYI it would be a big help for reviewing if the commits were cleaned up, especially if passing tests are added in their own commit (showing the old behavior) and then the feature work happens in the follow up that updates the tests so they still pass.

TanmayArya-1p · 2025-12-05T14:56:34Z

Sure, i'll clean up the commit history

epage · 2025-12-05T17:42:09Z

src/cargo/ops/cargo_compile/mod.rs

+                    None
+                }
+            }
+            _ => None,


Can we explicitly enumerate all TargetKinds so the compiler can remind us to re-evaluate this if a new variant is added?

epage · 2025-12-05T17:43:01Z

Thanks, this is looking great! Just adjusting the match for maintainability and this is good to go!

Update cargo submodule 27 commits in 2c283a9a5c5968eeb9a8f12313f04feb1ff8dfac..c46423de7351e3c4c734b2faa86088a9f5d1302b 2025-12-04 16:47:28 +0000 to 2025-12-12 23:16:12 +0000 - feat(report): cargo report timings HTML replay (rust-lang/cargo#16377) - feat: stabilize `-Zconfig-include` (rust-lang/cargo#16284) - fix(package): Don't verify registry for --list (rust-lang/cargo#16341) - Fixed incorrect locking logic when artifact-dir == build-dir (rust-lang/cargo#16385) - feat(log): make timing messages ready for HTML replay (rust-lang/cargo#16382) - chore(deps): update msrv (1 version) to v1.92 (rust-lang/cargo#16381) - Downgrade curl-sys to 0.4.83 (rust-lang/cargo#16379) - fix(timing): more self-contained timing/log data (rust-lang/cargo#16378) - test: update to `proc_macro::tracked::path` (rust-lang/cargo#16380) - refactor(lint): move lints to separate modules (rust-lang/cargo#16364) - fix(index): Apply feedback from Cargo team (rust-lang/cargo#16369) - fix(lints): handle lints separately at ws pkg level (rust-lang/cargo#16367) - feat(lint): new `implicit_minimum_version_req` lint (rust-lang/cargo#16321) - fix(info): default to local without explicit reg (rust-lang/cargo#16358) - Remove `[no-mentions]` handler in our triagebot config (rust-lang/cargo#16361) - Don't read the config file twice when $CARGO_HOME is a symlink (rust-lang/cargo#16325) - fix(timings): forgot to negate filter (rust-lang/cargo#16352) - fix(doctest): Include all search paths with new build layout (rust-lang/cargo#16348) - fix(layout): Remove hashes from bins in new layout (rust-lang/cargo#16351) - docs(faq): Include an entry on disk space (rust-lang/cargo#16349) - feat(timings): derive concurrency data from unit data (rust-lang/cargo#16350) - perf(layout): Use unit_id, not pkg hash, for bin/lib pkg_dirs for new layout (rust-lang/cargo#16345) - Validate target source paths before compilation with clearer errors (rust-lang/cargo#16338) - test(doc): Remove unused build script (rust-lang/cargo#16344) - refactor(timings): store UnitData in RenderContext instead (rust-lang/cargo#16346) - perf(clean): Optimize (legacy) clean with multiple -p specifiers (rust-lang/cargo#16264) - test: Adjust output for out-of-tree build-dir (rust-lang/cargo#16343)

Update cargo submodule 29 commits in 2c283a9a5c5968eeb9a8f12313f04feb1ff8dfac..e91b2baa632c0c7e84216c91ecfe107c37d887c1 2025-12-04 16:47:28 +0000 to 2025-12-13 16:29:21 +0000 - refactor(lints): move from cargo::util::lints to cargo::lints (rust-lang/cargo#16392) - test(lint): redact more due to line got omitted (rust-lang/cargo#16391) - feat(report): cargo report timings HTML replay (rust-lang/cargo#16377) - feat: stabilize `-Zconfig-include` (rust-lang/cargo#16284) - fix(package): Don't verify registry for --list (rust-lang/cargo#16341) - Fixed incorrect locking logic when artifact-dir == build-dir (rust-lang/cargo#16385) - feat(log): make timing messages ready for HTML replay (rust-lang/cargo#16382) - chore(deps): update msrv (1 version) to v1.92 (rust-lang/cargo#16381) - Downgrade curl-sys to 0.4.83 (rust-lang/cargo#16379) - fix(timing): more self-contained timing/log data (rust-lang/cargo#16378) - test: update to `proc_macro::tracked::path` (rust-lang/cargo#16380) - refactor(lint): move lints to separate modules (rust-lang/cargo#16364) - fix(index): Apply feedback from Cargo team (rust-lang/cargo#16369) - fix(lints): handle lints separately at ws pkg level (rust-lang/cargo#16367) - feat(lint): new `implicit_minimum_version_req` lint (rust-lang/cargo#16321) - fix(info): default to local without explicit reg (rust-lang/cargo#16358) - Remove `[no-mentions]` handler in our triagebot config (rust-lang/cargo#16361) - Don't read the config file twice when $CARGO_HOME is a symlink (rust-lang/cargo#16325) - fix(timings): forgot to negate filter (rust-lang/cargo#16352) - fix(doctest): Include all search paths with new build layout (rust-lang/cargo#16348) - fix(layout): Remove hashes from bins in new layout (rust-lang/cargo#16351) - docs(faq): Include an entry on disk space (rust-lang/cargo#16349) - feat(timings): derive concurrency data from unit data (rust-lang/cargo#16350) - perf(layout): Use unit_id, not pkg hash, for bin/lib pkg_dirs for new layout (rust-lang/cargo#16345) - Validate target source paths before compilation with clearer errors (rust-lang/cargo#16338) - test(doc): Remove unused build script (rust-lang/cargo#16344) - refactor(timings): store UnitData in RenderContext instead (rust-lang/cargo#16346) - perf(clean): Optimize (legacy) clean with multiple -p specifiers (rust-lang/cargo#16264) - test: Adjust output for out-of-tree build-dir (rust-lang/cargo#16343)

TanmayArya-1p marked this pull request as ready for review December 4, 2025 10:20

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Dec 4, 2025

rustbot assigned epage Dec 4, 2025