fix(frontend): fixed addFileSystem race

With latest changes it is more important to load main script
UISourceCode on time. This patch forces loading of main script
ahead of time.

front_end/ndb/FileSystem.js

@@ -50,6 +50,10 @@ Ndb.FileSystem = class extends Persistence.PlatformFileSystem {
     await this._fsService.startWatcher(this._embedderPath, this._excludePattern(), rpc.handle(this));
   }
 
+  forceFileLoad(scriptName) {
+    return this._fsService.forceFileLoad(scriptName);
+  }
+
   /**
    * @override
    * @return {!Array<string>}

front_end/ndb/NdbMain.js

@@ -32,7 +32,9 @@ Ndb.NdbMain = class extends Common.Object {
     const setting = Persistence.isolatedFileSystemManager.workspaceFolderExcludePatternSetting();
     setting.set(Ndb.NdbMain._defaultExcludePattern().join('|'));
     Ndb.nodeProcessManager = await Ndb.NodeProcessManager.create(SDK.targetManager);
-    this._addDefaultFileSystem();
+
+    const {cwd} = await Ndb.processInfo();
+    await Ndb.nodeProcessManager.addFileSystem(cwd);
 
     await new Promise(resolve => SDK.initMainConnection(resolve));
     // Create root Main target.
@@ -50,11 +52,6 @@ Ndb.NdbMain = class extends Common.Object {
     this._repl();
   }
 
-  async _addDefaultFileSystem() {
-    const info = await Ndb.processInfo();
-    await Ndb.nodeProcessManager.addFileSystem(info.cwd);
-  }
-
   async _repl() {
     const code = btoa(`console.log('Welcome to the ndb %cR%cE%cP%cL%c!',
       'color:#8bc34a', 'color:#ffc107', 'color:#ff5722', 'color:#2196f3', 'color:inherit');
@@ -185,18 +182,27 @@ Ndb.NodeProcessManager = class extends Common.Object {
     return this._processes.get(target.id()) || null;
   }
 
-  async addFileSystem(cwd) {
+  /**
+   * @param {string} cwd
+   * @param {string=} mainFileName
+   * @return {!Promise}
+   */
+  async addFileSystem(cwd, mainFileName) {
     let promise = this._cwds.get(cwd);
     if (!promise) {
       async function innerAdd() {
         const cwdUrl = Common.ParsedURL.platformPathToURL(cwd);
         const fileSystemManager = Persistence.isolatedFileSystemManager;
-        fileSystemManager.addPlatformFileSystem(cwdUrl, await Ndb.FileSystem.create(fileSystemManager, cwd, cwdUrl));
+        const fs = await Ndb.FileSystem.create(fileSystemManager, cwd, cwdUrl, mainFileName);
+        fileSystemManager.addPlatformFileSystem(cwdUrl, fs);
+        return fs;
       }
       promise = innerAdd();
       this._cwds.set(cwd, promise);
     }
-    return promise;
+    if (mainFileName)
+      await (await promise).forceFileLoad(mainFileName);
+    await promise;
   }
 
   async detected(id) {
@@ -220,7 +226,7 @@ Ndb.NodeProcessManager = class extends Common.Object {
       UI.context.setFlavor(SDK.ExecutionContext, executionContext);
     }
 
-    await this.addFileSystem(info.cwd);
+    await this.addFileSystem(info.cwd, info.scriptName);
     if (info.scriptName) {
       const scriptURL = Common.ParsedURL.platformPathToURL(info.scriptName);
       const uiSourceCode = Workspace.workspace.uiSourceCodeForURL(scriptURL);

services/file_system.js

@@ -1,13 +1,19 @@
+const fs = require('fs');
+
 const { rpc, rpc_process } = require('carlo/rpc');
 const chokidar = require('chokidar');
 
 class FileSystemHandler {
   constructor() {
     require('../lib/process_utility.js')('file_system', () => this.dispose());
     this._watcher = null;
+    this._embedderPath = '';
+    this._client = null;
   }
 
-  startWatcher(embedderPath, exludePattern, client) {
+  startWatcher(embedderPath, exludePattern, client, mainFileName) {
+    this._embedderPath = embedderPath;
+    this._client = client;
     this._watcher = chokidar.watch([embedderPath], {
       ignored: new RegExp(exludePattern),
       awaitWriteFinish: true,
@@ -27,6 +33,11 @@ class FileSystemHandler {
     this._watcher.on('error', console.error);
   }
 
+  forceFileLoad(fileName) {
+    if (fileName.startsWith(this._embedderPath) && fs.existsSync(fileName))
+      this._client.filesChanged([{type: 'add', name: fileName}]);
+  }
+
   dispose() {
     this._watcher.close();
     Promise.resolve().then(() => process.exit(0));