From 9adec6a59d25f7fe100eded52d2c3cb75bb5c582 Mon Sep 17 00:00:00 2001
From: David Calavera <1050+calavera@users.noreply.github.com>
Date: Thu, 24 Sep 2026 12:41:49 -0700
Subject: [PATCH] Rust: keep dependencies' build scripts in the target archive

A workspace crate with a build.rs added the build-script-build target
name to the skip pattern, which also matched every dependency's
compiled build script under target/debug/build/<dep>-<hash>/. Cargo
then rebuilt each dependency with a build script and all of its
dependents on every warm run.

Build-script targets are no longer part of the pattern; the package
name already covers the workspace's own build directories. The Rust
key gains an archive revision so entries saved without the scripts are
replaced instead of kept as unchanged.
---
 src/lib/languages.js | 11 +++++++++--
 test/cache.test.js   |  4 ++++
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/lib/languages.js b/src/lib/languages.js
index 3d67f6f..527fb4f 100644
--- a/src/lib/languages.js
+++ b/src/lib/languages.js
@@ -114,7 +114,12 @@ function workspaceArtifacts(roots) {
     if (!metadata) continue;
     try {
       for (const pkg of JSON.parse(metadata).packages) {
-        for (const name of [pkg.name, ...pkg.targets.map((target) => target.name)]) {
+        // Every build script's target is named build-script-build, so its name
+        // would match each dependency's compiled script, and a missing script
+        // rebuilds the crate and all its dependents. The package name already
+        // covers the workspace's own build/<crate>-<hash>/ directories.
+        const targets = pkg.targets.filter((target) => !target.kind.includes('custom-build'));
+        for (const name of [pkg.name, ...targets.map((target) => target.name)]) {
           names.add(name);
           names.add(name.replace(/-/g, '_'));
         }
@@ -169,7 +174,9 @@ const SPECS = {
       if (fs.existsSync(path.join(bin, 'rustup')) || fs.existsSync(path.join(bin, 'cargo'))) core.addPath(bin);
     },
     version() {
-      return commandOutput('rustc', ['-vV']);
+      // The revision changes the key when the archived files change, so
+      // entries saved without dependencies' build scripts are replaced.
+      return `${commandOutput('rustc', ['-vV'])}\narchive-revision: 2`;
     },
   },
   node: {
diff --git a/test/cache.test.js b/test/cache.test.js
index 9e59864..b87fbd8 100644
--- a/test/cache.test.js
+++ b/test/cache.test.js
@@ -440,6 +440,7 @@ test('drops workspace crate artifacts but keeps dependencies', { skip: !hasCargo
   const root = path.join(sandbox, 'crate');
   write(path.join(root, 'Cargo.toml'), '[package]\nname = "my-app"\nversion = "0.1.0"\nedition = "2021"\n');
   write(path.join(root, 'src', 'main.rs'), 'fn main() {}\n');
+  write(path.join(root, 'build.rs'), 'fn main() {}\n');
   const debug = path.join(root, 'target', 'debug');
   fs.mkdirSync(path.join(debug, 'deps'), { recursive: true });
   // cargo needs the real toolchain home to answer metadata.
@@ -453,6 +454,9 @@ test('drops workspace crate artifacts but keeps dependencies', { skip: !hasCargo
   assert.ok(skip(debug, 'my-app'), 'uplifted binary');
   for (const name of [`libserde-${hash}.rlib`, `my_app_utils-${hash}.rlib`, 'serde-1.0']) assert.ok(!skip(deps, name), name);
   assert.ok(!skip(path.join(root, 'elsewhere'), 'my-app'), 'uplifted names only next to deps/');
+  // A dependency's compiled build script, which the workspace's build.rs shares a target name with.
+  const script = path.join(debug, 'build', `libc-${hash}`);
+  for (const name of [`build_script_build-${hash}`, `build_script_build-${hash}.d`, 'build-script-build']) assert.ok(!skip(script, name), name);
 });
 
 test('keys on lockfiles, falling back to manifests', () => {