chore(studio): address cleanup review follow-ups

Three targeted fixes from the self-review pass on 7ceead9:

- Collapse the renderer dev port to a single source of truth.
  scripts/renderer-dev-config.mjs now owns host/port/URL and is
  imported by rsbuild.config.ts, wait-for-electron-build.mjs and a
  new launch-electron-dev.mjs launcher that injects the env var for
  electron. The dev script in package.json no longer hardcodes the
  URL, so the port lives in exactly one place.
- Wrap the non-ENOENT throw in readMtimeMs with a contextual Error
  (file path + original message via cause), so unexpected IO failures
  during the dev gate point directly at the offending file.
- Add a regression test that createFreshBuildChecker propagates a
  non-ENOENT reader error instead of treating it as a missing file,
  locking in the narrowed catch behavior.

Validated with pnpm --filter studio build, pnpm --filter studio test,
and pnpm run lint.

Author: quanru

apps/studio/package.json

@@ -5,7 +5,7 @@
   "type": "module",
   "scripts": {
     "build": "rsbuild build && node scripts/sync-static-assets.mjs",
-    "dev": "concurrently -k -n build,app \"rsbuild dev\" \"node scripts/wait-for-electron-build.mjs && MIDSCENE_STUDIO_RENDERER_URL=http://127.0.0.1:3210 electron dist/main/main.cjs\"",
+    "dev": "concurrently -k -n build,app \"rsbuild dev\" \"node scripts/wait-for-electron-build.mjs && node scripts/launch-electron-dev.mjs\"",
     "preview": "rsbuild preview --environment renderer",
     "start": "node scripts/sync-static-assets.mjs && electron dist/main/main.cjs",
     "test": "vitest run"

apps/studio/rsbuild.config.ts

@@ -3,14 +3,14 @@ import { pluginLess } from '@rsbuild/plugin-less';
 import { pluginReact } from '@rsbuild/plugin-react';
 import { pluginTypeCheck } from '@rsbuild/plugin-type-check';
 import { version as appVersion } from './package.json';
-
-// Must match the port used by MIDSCENE_STUDIO_RENDERER_URL in the `dev`
-// script of package.json.
-const rendererDevPort = 3210;
+import {
+  rendererDevHost,
+  rendererDevPort,
+} from './scripts/renderer-dev-config.mjs';
 
 export default defineConfig({
   server: {
-    host: '127.0.0.1',
+    host: rendererDevHost,
     port: rendererDevPort,
   },
   dev: {

apps/studio/scripts/launch-electron-dev.mjs

@@ -0,0 +1,37 @@
+import { spawn } from 'node:child_process';
+import { createRequire } from 'node:module';
+import path from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { rendererDevUrl } from './renderer-dev-config.mjs';
+
+// Spawns Electron with MIDSCENE_STUDIO_RENDERER_URL sourced from the shared
+// dev config, so the port is not duplicated in package.json scripts.
+const require = createRequire(import.meta.url);
+const electronBinary = require('electron');
+const rootDir = path.resolve(
+  path.dirname(fileURLToPath(import.meta.url)),
+  '..',
+);
+
+const child = spawn(
+  electronBinary,
+  [path.join(rootDir, 'dist/main/main.cjs')],
+  {
+    env: { ...process.env, MIDSCENE_STUDIO_RENDERER_URL: rendererDevUrl },
+    stdio: 'inherit',
+  },
+);
+
+const forwardSignal = (signal) => {
+  if (!child.killed) child.kill(signal);
+};
+process.on('SIGINT', forwardSignal);
+process.on('SIGTERM', forwardSignal);
+
+child.on('exit', (code, signal) => {
+  if (signal) {
+    process.kill(process.pid, signal);
+    return;
+  }
+  process.exit(code ?? 0);
+});

apps/studio/scripts/renderer-dev-config.mjs

@@ -0,0 +1,8 @@
+// Single source of truth for the renderer dev server host/port.
+// Imported by rsbuild.config.ts (to bind the dev server), by
+// scripts/wait-for-electron-build.mjs (to probe readiness) and by
+// scripts/launch-electron-dev.mjs (to tell the main process where
+// to load from via MIDSCENE_STUDIO_RENDERER_URL).
+export const rendererDevHost = '127.0.0.1';
+export const rendererDevPort = 3210;
+export const rendererDevUrl = `http://${rendererDevHost}:${rendererDevPort}`;

apps/studio/scripts/wait-for-electron-build.mjs

@@ -2,6 +2,7 @@ import fs from 'node:fs';
 import http from 'node:http';
 import path from 'node:path';
 import { fileURLToPath, pathToFileURL } from 'node:url';
+import { rendererDevUrl } from './renderer-dev-config.mjs';
 
 const __filename = fileURLToPath(import.meta.url);
 const __dirname = path.dirname(__filename);
@@ -12,7 +13,7 @@ export const defaultRequiredFiles = [
   path.join(rootDir, 'dist/preload/preload.cjs'),
 ];
 
-export const defaultRendererUrl = 'http://127.0.0.1:3210';
+export const defaultRendererUrl = rendererDevUrl;
 export const defaultMaxWaitMs = 180000;
 export const defaultPollIntervalMs = 500;
 
@@ -26,7 +27,12 @@ export const readMtimeMs = (file) => {
     // (permission denied, IO error, ...) should surface instead of being
     // silently swallowed into a stale-build state.
     if (error && error.code === 'ENOENT') return null;
-    throw error;
+    throw new Error(
+      `wait-for-electron-build: failed to stat ${file}: ${
+        error instanceof Error ? error.message : String(error)
+      }`,
+      { cause: error },
+    );
   }
 };
 

apps/studio/tests/wait-for-electron-build.test.mjs

@@ -85,6 +85,22 @@ describe('createFreshBuildChecker', () => {
     // fallback, so equal-mtime must stay false.
     expect(isFresh()).toBe(false);
   });
+
+  it('propagates non-ENOENT read errors instead of treating them as missing files', () => {
+    // Regression guard: readMtimeMs narrows its catch to ENOENT so real IO
+    // errors (permission denied, disk failure, ...) surface instead of being
+    // silently reinterpreted as "file not built yet". If someone widens the
+    // catch back to `catch {}`, this test must break.
+    const throwingReader = () => {
+      const error = new Error('permission denied');
+      error.code = 'EACCES';
+      throw error;
+    };
+
+    expect(() => createFreshBuildChecker([FILE_A], throwingReader)).toThrow(
+      /permission denied/,
+    );
+  });
 });
 
 describe('waitForBuild', () => {