fix(test): avoid walking unit-fast candidate roots

test/vitest-unit-fast-config.test.ts

@@ -1,3 +1,4 @@
+import { spawnSync } from "node:child_process";
 import { describe, expect, it } from "vitest";
 import { createCommandsLightVitestConfig } from "./vitest/vitest.commands-light.config.ts";
 import { createPluginSdkLightVitestConfig } from "./vitest/vitest.plugin-sdk-light.config.ts";
@@ -49,6 +50,31 @@ function collectUnroutedForcedFiles(
 }
 
 describe("unit-fast vitest lane", () => {
+  it("loads the config without recursively walking repo roots", () => {
+    const script = `
+      import fs from "node:fs";
+      let readdirSyncCalls = 0;
+      const originalReaddirSync = fs.readdirSync;
+      fs.readdirSync = function patchedReaddirSync(...args) {
+        readdirSyncCalls += 1;
+        return originalReaddirSync.apply(this, args);
+      };
+      await import("./test/vitest/vitest.unit-fast.config.ts?io-probe=" + Date.now());
+      console.log(readdirSyncCalls);
+    `;
+    const result = spawnSync(
+      process.execPath,
+      ["--import", "tsx", "--input-type=module", "-e", script],
+      {
+        cwd: process.cwd(),
+        encoding: "utf8",
+      },
+    );
+
+    expect(result.status, result.stderr).toBe(0);
+    expect(Number(result.stdout.trim())).toBeLessThan(20);
+  });
+
   it("runs cache-friendly tests without the reset-heavy runner or runtime setup", () => {
     const config = createUnitFastVitestConfig({});
     const testConfig = requireTestConfig(config);

test/vitest/vitest.unit-fast-paths.mjs

@@ -1,3 +1,4 @@
+import { spawnSync } from "node:child_process";
 import fs from "node:fs";
 import path from "node:path";
 import {
@@ -309,15 +310,32 @@ function walkFiles(directory, files = []) {
 
 const walkedTestFilesByCwd = new Map();
 
+function collectRepoTestFilesFromGit(cwd) {
+  const result = spawnSync("git", ["ls-files", "--", "src", "packages", "test"], {
+    cwd,
+    encoding: "utf8",
+    stdio: ["ignore", "pipe", "ignore"],
+  });
+  if (result.status !== 0) {
+    return null;
+  }
+  return result.stdout
+    .split("\n")
+    .map((file) => normalizeRepoPath(file.trim()))
+    .filter((file) => file.endsWith(".test.ts"));
+}
+
 function collectRepoTestFiles(cwd) {
   const normalizedCwd = normalizeRepoPath(cwd);
   const cached = walkedTestFilesByCwd.get(normalizedCwd);
   if (cached) {
     return cached;
   }
-  const files = ["src", "packages", "test"]
-    .flatMap((directory) => walkFiles(path.join(cwd, directory)))
-    .map((file) => normalizeRepoPath(path.relative(cwd, file)));
+  const files =
+    collectRepoTestFilesFromGit(cwd) ??
+    ["src", "packages", "test"]
+      .flatMap((directory) => walkFiles(path.join(cwd, directory)))
+      .map((file) => normalizeRepoPath(path.relative(cwd, file)));
   walkedTestFilesByCwd.set(normalizedCwd, files);
   return files;
 }