Add dev runner snapshot race regression test

server/src/__tests__/dev-runner-snapshot.test.ts

@@ -0,0 +1,88 @@
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+import { afterEach, describe, expect, it } from "vitest";
+import {
+  collectWatchedSnapshot,
+  diffSnapshots,
+  readSignature,
+} from "../../../scripts/dev-runner-snapshot.mjs";
+
+const tempRoots = new Set<string>();
+
+afterEach(() => {
+  for (const root of tempRoots) {
+    fs.rmSync(root, { recursive: true, force: true });
+  }
+  tempRoots.clear();
+});
+
+function createTempRoot(prefix: string): string {
+  const root = fs.mkdtempSync(path.join(os.tmpdir(), prefix));
+  tempRoots.add(root);
+  return root;
+}
+
+function createSnapshotOptions(root: string) {
+  return {
+    repoRoot: root,
+    watchedDirectories: [path.join(root, "server")],
+    watchedFiles: [path.join(root, "package.json")],
+    ignoredDirectoryNames: new Set(["node_modules"]),
+    ignoredRelativePaths: new Set([".paperclip/dev-server-status.json"]),
+  };
+}
+
+describe("dev-runner watched snapshot", () => {
+  it("skips files that disappear between directory listing and stat", () => {
+    const root = createTempRoot("paperclip-dev-runner-snapshot-file-race-");
+    const serverDir = path.join(root, "server");
+    const sourcePath = path.join(serverDir, "index.ts");
+    fs.mkdirSync(serverDir, { recursive: true });
+    fs.writeFileSync(sourcePath, "console.log('boot');\n", "utf8");
+
+    const fileSystem = {
+      existsSync: fs.existsSync,
+      readdirSync: fs.readdirSync,
+      statSync(target: fs.PathLike, options?: fs.StatOptions) {
+        if (target === sourcePath) {
+          fs.rmSync(sourcePath, { force: true });
+        }
+        return fs.statSync(target, options);
+      },
+    };
+
+    expect(() => collectWatchedSnapshot({ ...createSnapshotOptions(root), fileSystem })).not.toThrow();
+    expect(collectWatchedSnapshot(createSnapshotOptions(root)).has("server/index.ts")).toBe(false);
+  });
+
+  it("skips directories that disappear before they can be read", () => {
+    const root = createTempRoot("paperclip-dev-runner-snapshot-dir-race-");
+    const serverDir = path.join(root, "server");
+    const routesDir = path.join(serverDir, "routes");
+    fs.mkdirSync(routesDir, { recursive: true });
+    fs.writeFileSync(path.join(routesDir, "health.ts"), "export const ok = true;\n", "utf8");
+
+    const fileSystem = {
+      existsSync: fs.existsSync,
+      readdirSync(target: fs.PathLike, options?: fs.ObjectEncodingOptions & { withFileTypes: true }) {
+        if (target === routesDir) {
+          fs.rmSync(routesDir, { recursive: true, force: true });
+        }
+        return fs.readdirSync(target, options);
+      },
+      statSync: fs.statSync,
+    };
+
+    expect(() => collectWatchedSnapshot({ ...createSnapshotOptions(root), fileSystem })).not.toThrow();
+    expect(collectWatchedSnapshot(createSnapshotOptions(root)).has("server/routes/health.ts")).toBe(false);
+  });
+
+  it("returns null for missing file signatures and reports deleted paths in diffs", () => {
+    const root = createTempRoot("paperclip-dev-runner-snapshot-diff-");
+    const missingPath = path.join(root, "server", "deleted.ts");
+
+    expect(readSignature(missingPath)).toBeNull();
+    expect(diffSnapshots(new Map([["server/deleted.ts", "1:1"]]), new Map())).toEqual(["server/deleted.ts"]);
+  });
+});