fix: do not watch directories in google3

In google3, all the dependencies of a TypeScript program are known ahead
of time and they are listed in `tsconfig.json`. For this reason, there
is no need to watch `node_modules` directory. Tsserver in google3 has
additonal patch that explicitly prohibits watching directories that start
with `/google/src`.

This was not detected during development because we did not actually use
the TypeScript module specified in `typescript.tsdk`. The dynamic
loading of the `typescript` module requires the server code to be
compiled in AMD first, which happens only during the production build.

Author: Keen Yee Liau

server/src/server.ts

@@ -27,19 +27,20 @@ const logger = createLogger({
 });
 
 const ts = resolveTsServer(options.tsProbeLocations);
-const ng = resolveNgLangSvc(options.ngProbeLocations, options.ivy);
+const isG3 = ts.resolvedPath.includes('/google3/');
+const ivy = isG3 ? true : options.ivy;
+const ng = resolveNgLangSvc(options.ngProbeLocations, ivy);
 
 // ServerHost provides native OS functionality
-const host = new ServerHost(options.ivy);
+const host = new ServerHost(ivy, isG3);
 
 // Establish a new server session that encapsulates lsp connection.
 const session = new Session({
   host,
   logger,
   ngPlugin: NGLANGSVC,  // TypeScript allows only package names as plugin names.
   resolvedNgLsPath: ng.resolvedPath,
-  resolvedTsLsPath: ts.resolvedPath,
-  ivy: options.ivy,
+  ivy,
   logToConsole: options.logToConsole,
 });
 

server/src/server_host.ts

@@ -9,6 +9,10 @@
 import * as ts from 'typescript/lib/tsserverlibrary';
 import {NGLANGSVC} from './version_provider';
 
+const NOOP_WATCHER: ts.FileWatcher = {
+  close() {},
+};
+
 /**
  * `ServerHost` is a wrapper around `ts.sys` for the Node system. In Node, all
  * optional methods of `ts.System` are implemented.
@@ -20,7 +24,7 @@ export class ServerHost implements ts.server.ServerHost {
   readonly newLine: string;
   readonly useCaseSensitiveFileNames: boolean;
 
-  constructor(private ivy: boolean) {
+  constructor(private ivy: boolean, readonly isG3: boolean) {
     this.args = ts.sys.args;
     this.newLine = ts.sys.newLine;
     this.useCaseSensitiveFileNames = ts.sys.useCaseSensitiveFileNames;
@@ -57,6 +61,9 @@ export class ServerHost implements ts.server.ServerHost {
 
   watchDirectory(path: string, callback: ts.DirectoryWatcherCallback, recursive?: boolean):
       ts.FileWatcher {
+    if (this.isG3 && path.startsWith('/google/src')) {
+      return NOOP_WATCHER;
+    }
     return ts.sys.watchDirectory!(path, callback, recursive);
   }
 

server/src/session.ts

@@ -7,6 +7,7 @@
  */
 
 import {isNgLanguageService, NgLanguageService, PluginConfig} from '@angular/language-service/api';
+import * as assert from 'assert';
 import * as ts from 'typescript/lib/tsserverlibrary';
 import * as lsp from 'vscode-languageserver/node';
 
@@ -27,7 +28,6 @@ export interface SessionOptions {
   logger: ts.server.Logger;
   ngPlugin: string;
   resolvedNgLsPath: string;
-  resolvedTsLsPath: string;
   ivy: boolean;
   logToConsole: boolean;
 }
@@ -115,8 +115,8 @@ export class Session {
       angularOnly: true,
       ivy: options.ivy,
     };
-    if (options.resolvedTsLsPath.includes('/google3/')) {
-      pluginConfig.ivy = true;
+    if (options.host.isG3) {
+      assert(options.ivy === true, 'Ivy LS must be used in google3');
       pluginConfig.forceStrictTemplates = true;
     }
     projSvc.configurePlugin({