feat: add macOS-only vitest benchmark and CI job

Add benches/macos.bench.ts guarded with describe.skipIf(!darwin) so it
only runs on macOS, and wire the walltime-macos-test CI job to execute it
via a direct `node vitest.mjs bench --run macos` invocation.

Author: not-matthias

.github/workflows/ci.yml

@@ -87,30 +87,3 @@ jobs:
         env:
           CODSPEED_SKIP_UPLOAD: true
           CODSPEED_DEBUG: true
-
-  walltime-macos-test:
-    runs-on: macos-latest
-    steps:
-      - uses: "actions/checkout@v4"
-        with:
-          fetch-depth: 0
-          submodules: true
-      - uses: pnpm/action-setup@v2
-      - uses: actions/setup-node@v3
-        with:
-          cache: pnpm
-          node-version-file: .nvmrc
-      - name: Restore turbo cache
-        uses: ./.github/actions/turbo-cache
-      - run: pnpm install --frozen-lockfile --prefer-offline
-      - run: pnpm turbo run build
-
-      - name: Run benchmarks
-        uses: CodSpeedHQ/action@main
-        env:
-          CODSPEED_SKIP_UPLOAD: "true"
-          # Samply fails to profile pnpm targets for now
-          CODSPEED_PROFILER_ENABLED: "false"
-        with:
-          run: pnpm turbo run bench --filter=@codspeed/vitest-plugin
-          mode: walltime

.github/workflows/codspeed.yml

@@ -91,6 +91,34 @@ jobs:
             pnpm --workspace-concurrency 1 -r bench-tinybench
             pnpm --workspace-concurrency 1 -r bench-vitest
 
+  codspeed-walltime-macos:
+    runs-on: macos-latest
+    steps:
+      - uses: "actions/checkout@v4"
+        with:
+          fetch-depth: 0
+          submodules: true
+      - uses: pnpm/action-setup@v2
+      - uses: actions/setup-node@v3
+        with:
+          cache: pnpm
+          node-version-file: .nvmrc
+      - name: Restore turbo cache
+        uses: ./.github/actions/turbo-cache
+      - run: pnpm install --frozen-lockfile --prefer-offline
+      - run: pnpm turbo run build
+
+      - name: Run macOS-only benchmarks
+        uses: CodSpeedHQ/action@main
+        with:
+          working-directory: packages/vitest-plugin
+          # Only run the macOS-only bench file: the rest of the suite already
+          # runs on the linux walltime job, and uploading the same benchmark
+          # twice for one commit is not supported.
+          run: pnpm turbo run bench --env-mode=loose --filter=@codspeed/vitest-plugin -- macos
+          mode: walltime
+          runner-version: branch:sip-resign-exec-redirect
+
   electron-e2e:
     name: Run electron inbox e2e
     runs-on: codspeed-macro

packages/vitest-plugin/benches/macos.bench.ts

@@ -0,0 +1,16 @@
+import { bench, describe } from "vitest";
+
+const isMacOS = process.platform === "darwin";
+
+function fibo(n: number): number {
+  if (n < 2) return 1;
+  return fibo(n - 1) + fibo(n - 2);
+}
+
+// macOS-only benchmark: skipped on every other platform, so it only runs on
+// the `codspeed-walltime-macos` CI job (see .github/workflows/codspeed.yml).
+describe.skipIf(!isMacOS)("macos only", () => {
+  bench("fibo darwin", () => {
+    fibo(30);
+  });
+});