feat(filesearch): Introduce non-recursive file search strategy (#6087)

Co-authored-by: Jacob Richman <jacob314@gmail.com>
Co-authored-by: Bryant Chandler <bryantchandler@chromium.org>

packages/core/src/utils/filesearch/crawler.ts

@@ -0,0 +1,85 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import path from 'node:path';
+import { fdir } from 'fdir';
+import { Ignore } from './ignore.js';
+import * as cache from './crawlCache.js';
+
+export interface CrawlOptions {
+  // The directory to start the crawl from.
+  crawlDirectory: string;
+  // The project's root directory, for path relativity.
+  cwd: string;
+  // The fdir maxDepth option.
+  maxDepth?: number;
+  // A pre-configured Ignore instance.
+  ignore: Ignore;
+  // Caching options.
+  cache: boolean;
+  cacheTtl: number;
+}
+
+function toPosixPath(p: string) {
+  return p.split(path.sep).join(path.posix.sep);
+}
+
+export async function crawl(options: CrawlOptions): Promise<string[]> {
+  if (options.cache) {
+    const cacheKey = cache.getCacheKey(
+      options.crawlDirectory,
+      options.ignore.getFingerprint(),
+      options.maxDepth,
+    );
+    const cachedResults = cache.read(cacheKey);
+
+    if (cachedResults) {
+      return cachedResults;
+    }
+  }
+
+  const posixCwd = toPosixPath(options.cwd);
+  const posixCrawlDirectory = toPosixPath(options.crawlDirectory);
+
+  let results: string[];
+  try {
+    const dirFilter = options.ignore.getDirectoryFilter();
+    const api = new fdir()
+      .withRelativePaths()
+      .withDirs()
+      .withPathSeparator('/') // Always use unix style paths
+      .exclude((_, dirPath) => {
+        const relativePath = path.posix.relative(posixCrawlDirectory, dirPath);
+        return dirFilter(`${relativePath}/`);
+      });
+
+    if (options.maxDepth !== undefined) {
+      api.withMaxDepth(options.maxDepth);
+    }
+
+    results = await api.crawl(options.crawlDirectory).withPromise();
+  } catch (_e) {
+    // The directory probably doesn't exist.
+    return [];
+  }
+
+  const relativeToCrawlDir = path.posix.relative(posixCwd, posixCrawlDirectory);
+
+  const relativeToCwdResults = results.map((p) =>
+    path.posix.join(relativeToCrawlDir, p),
+  );
+
+  if (options.cache) {
+    const cacheKey = cache.getCacheKey(
+      options.crawlDirectory,
+      options.ignore.getFingerprint(),
+      options.maxDepth,
+    );
+    cache.write(cacheKey, relativeToCwdResults, options.cacheTtl * 1000);
+  }
+
+  return relativeToCwdResults;
+}