test: consolidate sessions_spawn and guardrail helpers

src/test-utils/repo-scan.ts

@@ -0,0 +1,78 @@
+import fs from "node:fs/promises";
+import path from "node:path";
+
+export const DEFAULT_REPO_SCAN_SKIP_DIR_NAMES = new Set([".git", "dist", "node_modules"]);
+
+export type RepoFileScanOptions = {
+  roots: readonly string[];
+  extensions: readonly string[];
+  skipDirNames?: ReadonlySet<string>;
+  skipHiddenDirectories?: boolean;
+  shouldIncludeFile?: (relativePath: string) => boolean;
+};
+
+type PendingDir = {
+  absolutePath: string;
+};
+
+function shouldSkipDirectory(
+  name: string,
+  options: Pick<RepoFileScanOptions, "skipDirNames" | "skipHiddenDirectories">,
+): boolean {
+  if (options.skipHiddenDirectories && name.startsWith(".")) {
+    return true;
+  }
+  return (options.skipDirNames ?? DEFAULT_REPO_SCAN_SKIP_DIR_NAMES).has(name);
+}
+
+function hasAllowedExtension(fileName: string, extensions: readonly string[]): boolean {
+  return extensions.some((extension) => fileName.endsWith(extension));
+}
+
+export async function listRepoFiles(
+  repoRoot: string,
+  options: RepoFileScanOptions,
+): Promise<Array<string>> {
+  const files: Array<string> = [];
+  const pending: Array<PendingDir> = [];
+
+  for (const root of options.roots) {
+    const absolutePath = path.join(repoRoot, root);
+    try {
+      const stats = await fs.stat(absolutePath);
+      if (stats.isDirectory()) {
+        pending.push({ absolutePath });
+      }
+    } catch {
+      // Skip missing roots. Useful when extensions/ is absent.
+    }
+  }
+
+  while (pending.length > 0) {
+    const current = pending.pop();
+    if (!current) {
+      continue;
+    }
+    const entries = await fs.readdir(current.absolutePath, { withFileTypes: true });
+    for (const entry of entries) {
+      if (entry.isDirectory()) {
+        if (!shouldSkipDirectory(entry.name, options)) {
+          pending.push({ absolutePath: path.join(current.absolutePath, entry.name) });
+        }
+        continue;
+      }
+      if (!entry.isFile() || !hasAllowedExtension(entry.name, options.extensions)) {
+        continue;
+      }
+      const filePath = path.join(current.absolutePath, entry.name);
+      const relativePath = path.relative(repoRoot, filePath);
+      if (options.shouldIncludeFile && !options.shouldIncludeFile(relativePath)) {
+        continue;
+      }
+      files.push(filePath);
+    }
+  }
+
+  files.sort((a, b) => a.localeCompare(b));
+  return files;
+}