cargo clean: Add target directory validation by TanmayArya-1p · Pull Request #16712 · rust-lang/cargo

TanmayArya-1p · 2026-03-05T23:20:32Z

What does this PR try to resolve?

Fixes #9192

Implements the checks mentioned in this comment

To summarise, when cargo clean is run with a specified target directory:

If a target directory is explicitly passed via --target-dir: check if a valid CACHEDIR.TAG exists in the target directory and hard error otherwise.
In other cases where target directory is specified(via env vars or build config): emit a future incompat warning if the target directory does not contain a valid CACHEDIR.TAG

Tests

I've added 3 sets of unit tests for:

When --target-dir is used explicitly
When target directory is specified via the build config
When target directory is specified via the CARGO_TARGET_DIR env variable

Let me know if there is a case I've missed or if i need to merge multiple tests into a single one.

TanmayArya-1p · 2026-03-05T23:22:38Z

I also noticed that if a file path is passed via --target-dir, it gets deleted without validation. I was wondering if we require checks for this as well?

rustbot · 2026-03-05T23:27:20Z

r? @weihanglo

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The reviewer was selected based on:

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

Some nitpicks but general good. Thank you!

View changes since this review

weihanglo · 2026-03-06T01:23:00Z

src/cargo/ops/cargo_clean.rs

    let mut clean_ctx = CleanContext::new(gctx);
    clean_ctx.dry_run = opts.dry_run;

+    // TODO: validate if target_dir is not a file?


I also noticed that if a file path is passed via --target-dir, it gets deleted without validation. I was wondering if we require checks for this as well?

That would be a behavior change. Currently you can do this

$ touch myfile $ cargo clean --target-dir myfile Removed 1 file

Though this is rare and personally I considered it unsupported use case. We probably want to address it as well.

weihanglo · 2026-03-06T01:27:50Z

src/cargo/ops/cargo_clean.rs

+        // if target_dir was passed explicitly via --target-dir, then hard error if validation fails
+        validate_target_dir_tag(target_dir.as_path_unlocked()).map_err(|err| {
+            anyhow!(
+                "cannot clean `{}`: {err:#}\n\


Why using alternate display here?

Any specific reason?

no specific reason, just a habit from another project. ill remove it since it shouldn't matter here

src/cargo/ops/cargo_clean.rs

TanmayArya-1p · 2026-03-06T12:44:44Z

thanks for the review :)
I made a few changes and fixed the things you pointed out, let me know if theres anything else that needs to be changed.

Also I noticed that the CI keeps failing in something totally unrelated. I see it's happening in other PRs as well. Any idea why this is happening?
Edit: Nevermind, I see #16714 addresses this

weihanglo · 2026-03-06T17:09:52Z

Also I noticed that the CI keeps failing in something totally unrelated. I see it's happening in other PRs as well. Any idea why this is happening?
Edit: Nevermind, I see #16714 addresses this

Feel free to rebase onto master!
Edit: actually you need to do that in order to make CI green and in a mergeable state

rustbot · 2026-03-06T17:12:51Z

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.

weihanglo

While this has been discussed within the team, this is a behavior change so I may start an FCP. Just FYI

View changes since this review

weihanglo · 2026-03-07T16:23:53Z

src/cargo/ops/cargo_clean.rs

+    const TAG_SIGNATURE: &[u8] = b"Signature: 8a477f597d28d172789f06886806bc55";
+
+    // if the path is not a dir then don't do anything
+    if !target_dir_path.is_dir() {


Do we want to warn for this case? Like the "/path/to/file does not appear to be a valid Cargo target directory"?

https://doc.rust-lang.org/cargo/commands/cargo-clean.html#option-cargo-clean---target-dir

--target-dir directory
Directory for all generated artifacts and intermediate files. May also be specified with the CARGO_TARGET_DIR environment variable, or the build.target-dir config value. Defaults to target in the root of the workspace.

since the docs are explicit about it being a directory, maybe we should probably hard error when target_dir points to a file. I can't imagine someones script would break if we add a check here.

That sounds good to me!

weihanglo · 2026-03-07T16:26:28Z

src/cargo/ops/cargo_clean.rs

+        // if target_dir was passed explicitly via --target-dir, then hard error if validation fails
+        validate_target_dir_tag(target_dir.as_path_unlocked()).map_err(|err| {
+            anyhow!(
+                "cannot clean `{}`: {err:#}\n\


Any specific reason?

TanmayArya-1p · 2026-03-07T21:06:12Z

Added a check(and test) to make sure target_dir is a directory when it is specified. Also, I wasnt happy with how the code looked so i refactored it a bit.

rustbot added A-cli Area: Command-line interface, option parsing, etc. Command-clean labels Mar 5, 2026

TanmayArya-1p marked this pull request as ready for review March 5, 2026 23:27

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Mar 5, 2026

rustbot assigned weihanglo Mar 5, 2026

weihanglo reviewed Mar 6, 2026

View reviewed changes

TanmayArya-1p force-pushed the clean-target-validation branch from 94c1489 to 94a4d66 Compare March 6, 2026 11:15

TanmayArya-1p force-pushed the clean-target-validation branch from 94a4d66 to c6cdaa1 Compare March 6, 2026 17:12

weihanglo reviewed Mar 7, 2026

View reviewed changes

TanmayArya-1p force-pushed the clean-target-validation branch from c6cdaa1 to f72fbd1 Compare March 7, 2026 17:55

TanmayArya-1p added 2 commits March 8, 2026 01:43

add tests showing cargo clean does not validate target dir

1cdad6a

cargo clean: add target dir validation

23c225b

TanmayArya-1p force-pushed the clean-target-validation branch from f72fbd1 to 23c225b Compare March 7, 2026 20:33

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TanmayArya-1p commented Mar 5, 2026

What does this PR try to resolve?

Tests

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