fix: set CARGO env var during rustc -vV probe by zhibisora · Pull Request #16811 · rust-lang/cargo

zhibisora · 2026-03-31T15:31:22Z

Summary

Set the CARGO environment variable when running the rustc -vV version probe, consistent with how Compilation::fill_env() sets it for all compilation invocations.

Problem

Since #13659, the -vV probe goes through RUSTC_WRAPPER and RUSTC_WORKSPACE_WRAPPER. However, the CARGO env var is not set during this probe. Tools like sccache depend on CARGO to detect the workspace wrapper pattern in their compiler detection logic (mozilla/sccache#1280), causing sccache to fail with "Compiler not supported" when a RUSTC_WORKSPACE_WRAPPER is present.

Solution

Add cmd.env(crate::CARGO_ENV, gctx.cargo_exe()?) before the -vV invocation in Rustc::new().

Test plan

Existing rustc_wrapper tests pass (8/8)
Manually verified: CARGO=$(which cargo) as a workaround resolves the issue

Closes #16805

rustbot · 2026-03-31T15:31:32Z

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

Thanks for the contribution. We expect a new test to be written for new behavior. We've also found it helpful to add the tests in a commit before the fix, reproducing the problem. See a working-in-progress note from epage: https://epage.github.io/dev/pr-style/#c-test

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Add a test that verifies whether the CARGO env var is set when the rustc wrapper is invoked during the -vV version probe. Currently it is not set, which causes tools like sccache to fail when RUSTC_WORKSPACE_WRAPPER is also present. See rust-lang#16805

The -vV probe goes through RUSTC_WRAPPER and RUSTC_WORKSPACE_WRAPPER since rust-lang#13659, but the CARGO env var was not set. Tools like sccache depend on CARGO to detect the workspace wrapper pattern in their compiler detection logic. Closes rust-lang#16805

zhibisora · 2026-03-31T17:09:49Z

Updated with two commits per C-TEST convention:

test: — adds a test that reproduces the current behavior (CARGO env var is not set during the -vV probe)
fix: — sets CARGO on the probe command and updates the test expectation

The test uses a custom wrapper that writes CARGO env var status to a file when invoked for -vV, since the probe's stderr is captured by cached_output and not visible in test output.

arlosi

Thanks!

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weihanglo

Thanks!

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Update cargo submodule 12 commits in 888f675344eb1cf2308fd53183e667bdd2c58e51..0c7d80bf5ad3b873a5dbf44e0185152890c6d18a 2026-03-30 16:59:25 +0000 to 2026-04-02 20:48:06 +0000 - refactor(network): use async for registry network operations (rust-lang/cargo#16745) - fix(compile): Don't hide hard warnings with build.warnings=allow (rust-lang/cargo#16827) - chore: Upgrade incompatible dependencies (rust-lang/cargo#16825) - fix(compile): build.warnings=allow should not hide denied diagnostics (rust-lang/cargo#16824) - fix(install): Ignore resolver.lockfile-path (rust-lang/cargo#16823) - chore(deps): update compatible (rust-lang/cargo#16820) - refactor(compile): Consolidate output options (rust-lang/cargo#16821) - refactor: Export public dependencies from internal crates (rust-lang/cargo#16819) - refactor(progress): Make the code more approachable (rust-lang/cargo#16813) - Simplified build script bin names in new layout (rust-lang/cargo#16812) - fix: set CARGO env var during rustc -vV probe (rust-lang/cargo#16811) - Split out `cargo-util-terminal` (rust-lang/cargo#16809) r? ghost

Update cargo submodule 15 commits in 888f675344eb1cf2308fd53183e667bdd2c58e51..a357df4c26fc14514e66aae2a269456b5545c7db 2026-03-30 16:59:25 +0000 to 2026-04-03 16:47:15 +0000 - chore: downgrade to libz-sys@1.1.24 (rust-lang/cargo#16833) - feat: add frame-pointers profile option (rust-lang/cargo#16742) - upgrade to gix@0.81.0 (rust-lang/cargo#16828) - refactor(network): use async for registry network operations (rust-lang/cargo#16745) - fix(compile): Don't hide hard warnings with build.warnings=allow (rust-lang/cargo#16827) - chore: Upgrade incompatible dependencies (rust-lang/cargo#16825) - fix(compile): build.warnings=allow should not hide denied diagnostics (rust-lang/cargo#16824) - fix(install): Ignore resolver.lockfile-path (rust-lang/cargo#16823) - chore(deps): update compatible (rust-lang/cargo#16820) - refactor(compile): Consolidate output options (rust-lang/cargo#16821) - refactor: Export public dependencies from internal crates (rust-lang/cargo#16819) - refactor(progress): Make the code more approachable (rust-lang/cargo#16813) - Simplified build script bin names in new layout (rust-lang/cargo#16812) - fix: set CARGO env var during rustc -vV probe (rust-lang/cargo#16811) - Split out `cargo-util-terminal` (rust-lang/cargo#16809)

rustbot assigned epage Mar 31, 2026

rustbot added A-cache-messages Area: caching of compiler messages S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Mar 31, 2026

weihanglo reviewed Mar 31, 2026

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zhibisora added 2 commits April 1, 2026 01:02

zhibisora force-pushed the fix-cargo-env-vv-probe branch from 40bcbe9 to e794ef7 Compare March 31, 2026 17:08

arlosi approved these changes Mar 31, 2026

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weihanglo approved these changes Mar 31, 2026

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weihanglo enabled auto-merge March 31, 2026 17:39

weihanglo added this pull request to the merge queue Mar 31, 2026

Merged via the queue into rust-lang:master with commit 9cb2a0c Mar 31, 2026
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rustbot removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Mar 31, 2026

weihanglo mentioned this pull request Apr 2, 2026

Update cargo submodule rust-lang/rust#154734

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rustbot added this to the 1.96.0 milestone Apr 7, 2026

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fix: set CARGO env var during rustc -vV probe#16811

fix: set CARGO env var during rustc -vV probe#16811
weihanglo merged 2 commits intorust-lang:masterfrom
zhibisora:fix-cargo-env-vv-probe

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zhibisora commented Mar 31, 2026

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