[jdx]

https://entire.io/gh/jdx/mise/trails/482

Parallel `cargo:` installs that fall back to a plain `cargo install` could corrupt the shared rustup toolchain (`could not rename 'component' file ... Directory not empty`, `detected conflict: 'bin/rust-gdb'`), because each `cargo` child can invoke rustup on its own. The lock added in #11794 only covered the core rust plugin.

The cargo backend now takes the same rust state lock (keyed on the resolved `RUSTUP_HOME`/`CARGO_HOME`) before running `cargo install`. Source builds with the same homes now run one at a time; binstall paths are unaffected.

Fixes #14041

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---

Note

Medium Risk
Touches install-time locking for shared rustup state; wrong home resolution could over- or under-serialize, but scope is limited to cargo install fallback paths.

Overview
Extends rustup state locking to the cargo backend so parallel cargo: installs that fall back to cargo install no longer race the core rust plugin on shared RUSTUP_HOME / CARGO_HOME (fixing rustup “component rename” / bin conflicts).

Before spawning cargo install, the cargo backend now holds the same filesystem locks the rust plugin uses. A new lock_rust_state_for_config helper resolves those homes from the effective child environment (process env, toolset env, and per-install env overrides). The rust module is re-exported as pub(crate) so the cargo backend can call it.

cargo-binstall paths that return early are unchanged; only source / cargo install fallbacks are serialized per resolved rust home pair.

^{Reviewed by Cursor Bugbot for commit ee119ae. Bugbot is set up for automated code reviews on this repo. Configure here.}

Summary by CodeRabbit

• Bug Fixes
  • Rust tool installations now coordinate access to the relevant Rust environments throughout the install process, helping prevent conflicting installs. Coordination uses the effective environment settings for each installation, including customized or unset Rust home directories, so concurrent installs with different configurations can proceed without interfering with one another.

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📝 Walkthrough

Walkthrough

Before the Cargo backend runs cargo install as a fallback, it now acquires Rust state locks for the resolved toolset and install environments. A crate-visible helper resolves the Rust homes and returns the lock handles.

Changes

Cargo Rust State Locking

Layer / File(s)	Summary
Acquire Rust state locks before cargo install src/plugins/core/rust.rs, src/plugins/core/mod.rs, src/backend/cargo.rs	A crate-visible helper overlays toolset environment values with install environment values, resolves Rust homes, and acquires their locks. The Cargo backend calls the helper before cargo install.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix · Severity of issue fixed: Medium

Sequence Diagram(s)

sequenceDiagram
  participant CargoBackend
  participant lock_rust_state_for_config
  participant RustStateLocks
  CargoBackend->>lock_rust_state_for_config: request locks for toolset and install environments
  lock_rust_state_for_config->>RustStateLocks: acquire locks for resolved Rust homes
  RustStateLocks-->>CargoBackend: return lock handles
  CargoBackend->>CargoBackend: run cargo install while locks remain held

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Suggested reviewers: marukome0743, risu729

Merge Risk: ⚪ Minimal · up to ee119

The reviewed change has no identified issue requiring a fix before merge.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 20.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 5 functions across 3 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main change: locking Rustup state across Cargo install fallbacks.
Linked Issues check	✅ Passed	Issue [#14041] requires the cargo backend to serialize cargo install against the Rust state lock, using the effective RUSTUP_HOME and CARGO_HOME. The cargo fallback acquires `lock_rust_state_for…
Out of Scope Changes check	✅ Passed	All changes support [#14041]. src/backend/cargo.rs acquires the lock for the source-install path, while src/plugins/core/rust.rs provides environment-aware access to the existing lock and `src/plu…

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[greptile-apps]

Confidence Score: 5/5

[Medium risk] Adds concurrency locking around Rust toolchain operations.

The PR appears safe to merge; no blocking issues remain.

What we checked:

• Overrides choose the same locks: Both paths apply toolset values before install_env. Both remove variables when their values request removal.

Summary

The PR makes source cargo install builds share Rust state locks with the core Rust plugin.

• Lock homes now follow the child’s inherited environment, toolset values, and install_env overrides.
• Removed home variables no longer fall back to settings or ambient values.
• Prebuilt installation paths are unchanged.
• The earlier, unnumbered finding about install_env overrides is addressed. No new actionable issues were found.

_{Reviews (6) · Last reviewed commit: "fix(cargo): lock the homes cargo's child..." · Reviewed by Greptile}

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Actionable comments posted: 1

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• 🪄 Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at @src/plugins/core/rust.rs:
- Around line 982-997: Update lock_rust_state_for_config to resolve Rust home
identities from Cargo’s effective environment, including tv.install_env(), so
the locks cover the same CARGO_HOME and RUSTUP_HOME used by
CargoBackend::install.

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🟡 Minor · Do not fall back to ambient homes when both variables are removed. · rust.rs:982-1000

src/plugins/core/rust.rs:982-1000
🩺 Stability & Availability | 🟡 Minor | ⚡ Quick win

Do not fall back to ambient homes when both variables are removed.

For a Git-backed Cargo install, install_env = { CARGO_HOME = false, RUSTUP_HOME = false } reaches the direct cargo install path. With custom ambient homes and no Rust-home setting overrides, the helper removes both keys but then selects those ambient homes. The child removes both variables and uses the standard homes. If [env] selects those standard homes for a concurrent core Rust install, the Rust install locks the standard paths while Cargo locks the custom paths. Cargo may invoke rustup, so the operations can change the same Rust state without sharing locks.

Removing only CARGO_HOME does not produce this fully disjoint lock set: RUSTUP_HOME remains in the effective environment and its lock remains shared when both installs use the same configuration.

Suggested fix

     }
     let settings = Settings::get();
+    let ambient_cargo_home = if matches!(
+        install_env.get("CARGO_HOME"),
+        Some(&crate::config::env_directive::EnvValue::Bool(false))
+    ) {
+        None
+    } else {
+        env::var_path("CARGO_HOME")
+    };
+    let ambient_rustup_home = if matches!(
+        install_env.get("RUSTUP_HOME"),
+        Some(&crate::config::env_directive::EnvValue::Bool(false))
+    ) {
+        None
+    } else {
+        env::var_path("RUSTUP_HOME")
+    };
     let homes = RustHomes::from_sources(
         &config_env,
         settings.rust.cargo_home.clone(),
-        env::var_path("CARGO_HOME"),
+        ambient_cargo_home,
         settings.rust.rustup_home.clone(),
-        env::var_path("RUSTUP_HOME"),
+        ambient_rustup_home,
     );

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Review comment at @src/plugins/core/rust.rs around lines 982 - 1000:
Update the ambient-home arguments passed to RustHomes::from_sources so an
explicit false directive for CARGO_HOME or RUSTUP_HOME prevents falling back to
that ambient variable. Preserve the existing settings and config_env precedence,
and continue using ambient homes when the corresponding install_env key is not
disabled.

---

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Outside diff comments:
Review comments at @src/plugins/core/rust.rs:
- Around line 982-1000: Update the ambient-home arguments passed to
RustHomes::from_sources so an explicit false directive for CARGO_HOME or
RUSTUP_HOME prevents falling back to that ambient variable. Preserve the
existing settings and config_env precedence, and continue using ambient homes
when the corresponding install_env key is not disabled.

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Inline comments:
Review comments at @src/plugins/core/rust.rs:
- Around line 993-997: Update the environment-unset handling around
config_env.shift_remove so removing CARGO_HOME also excludes MISE_CARGO_HOME,
and removing RUSTUP_HOME also excludes MISE_RUSTUP_HOME, before resolving
RustHomes; preserve unrelated environment entries.

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🟡 Minor · Use the same resolved Rust homes for locking and the Cargo child process. · cargo.rs:318-322

src/backend/cargo.rs:318-322
🩺 Stability & Availability | 🟡 Minor | ⚡ Quick win

Use the same resolved Rust homes for locking and the Cargo child process.

The in-process JoinSet passes each task the same config and ts, so it does not create different toolset homes within one mise install invocation. But two concurrent invocations can use different project configs. If both configs set distinct MISE_CARGO_HOME and MISE_RUSTUP_HOME values while both processes inherit the same standard CARGO_HOME and RUSTUP_HOME, the lock helper selects different home paths. The Cargo child still inherits the shared standard paths, so both invocations can run rustup against the same state without sharing a lock. Resolve the homes once and use those paths for both lock acquisition and the Cargo child environment.

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Review comment at @src/backend/cargo.rs around lines 318 - 322:
Update the Cargo install flow around toolset_env and lock_rust_state_for_config
to resolve the Rust and Cargo home paths once, then use those same resolved
paths both when acquiring the lock and when configuring the Cargo child process
environment.

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Outside diff comments:
Review comments at @src/backend/cargo.rs:
- Around line 318-322: Update the Cargo install flow around toolset_env and
lock_rust_state_for_config to resolve the Rust and Cargo home paths once, then
use those same resolved paths both when acquiring the lock and when configuring
the Cargo child process environment.

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[github-actions]

Instruction counts

benchmark	trend	instructions	Δ	wall (min)	Δ
env	▂▃▅▅█▁▂	27,279,282 → 27,290,912	+0.04%	19.40 → 19.68ms	+1.46%
hook-env	▁▃▆██▅▅	29,289,307 → 29,293,194	+0.01%	20.40 → 20.28ms	-0.60%
ls	▁▁▆█▇▅▅	31,011,881 → 31,008,715	-0.01%	21.15 → 21.19ms	+0.18%
registry	██▄▅▅▃▁	39,958,957 → 39,875,252	-0.21%	17.71 → 17.88ms	+1.00%
startup	▄▄▇▇█▄▁	10,887,928 → 10,868,698	-0.18%	11.53 → 11.97ms	+3.86%

No instruction-count regression above 1%.

_{Only instruction counts gate. Wall clock is shown for context — on identical hardware it moves 4-20% run to run.}

_{Measured by tak — instruction-counted CLI benchmarks, stored in this repository's git notes.}

_{ee119aecbfd1 vs 089285e90eb5 · measured on the runner, not pushed to the history.}