fix: check dev bundle exists when in debug mode (#456)

VS Code Insider launches extension in debug mode by defaul, but users
install prod bundle so we have to check whether dev bundle exists, and
fall back to prod bundle if it does not.

PR closes #449

Author: Keen Yee Liau

client/src/extension.ts

@@ -6,6 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
+import * as fs from 'fs';
 import * as path from 'path';
 import * as vscode from 'vscode';
 import * as lsp from 'vscode-languageclient';
@@ -17,35 +18,8 @@ export function activate(context: vscode.ExtensionContext) {
   // If the extension is launched in debug mode then the debug server options are used
   // Otherwise the run options are used
   const serverOptions: lsp.ServerOptions = {
-    run: {
-      module: context.asAbsolutePath(path.join('server')),
-      transport: lsp.TransportKind.ipc,
-      args: constructArgs(context, false /* debug */),
-      options: {
-        env: {
-          // Force TypeScript to use the non-polling version of the file watchers.
-          TSC_NONPOLLING_WATCHER: true,
-        },
-      },
-    },
-    debug: {
-      module: context.asAbsolutePath(path.join('server', 'out', 'server.js')),
-      transport: lsp.TransportKind.ipc,
-      args: constructArgs(context, true /* debug */),
-      options: {
-        env: {
-          // Force TypeScript to use the non-polling version of the file watchers.
-          TSC_NONPOLLING_WATCHER: true,
-          NG_DEBUG: true,
-        },
-        execArgv: [
-          // do not lazily evaluate the code so all breakpoints are respected
-          '--nolazy',
-          // If debugging port is changed, update .vscode/launch.json as well
-          '--inspect=6009',
-        ]
-      },
-    },
+    run: getServerOptions(context, false /* debug */),
+    debug: getServerOptions(context, true /* debug */),
   };
 
   // Options to control the language client
@@ -171,3 +145,40 @@ function constructArgs(ctx: vscode.ExtensionContext, debug: boolean): string[] {
 
   return args;
 }
+
+function getServerOptions(ctx: vscode.ExtensionContext, debug: boolean): lsp.NodeModule {
+  // Environment variables for server process
+  const prodEnv = {
+    // Force TypeScript to use the non-polling version of the file watchers.
+    TSC_NONPOLLING_WATCHER: true,
+  };
+  const devEnv = {
+    ...prodEnv,
+    NG_DEBUG: true,
+  };
+
+  // Node module for the language server
+  const prodBundle = ctx.asAbsolutePath('server');
+  const devBundle = ctx.asAbsolutePath(path.join('server', 'out', 'server.js'));
+
+  // Argv options for Node.js
+  const prodExecArgv: string[] = [];
+  const devExecArgv: string[] = [
+    // do not lazily evaluate the code so all breakpoints are respected
+    '--nolazy',
+    // If debugging port is changed, update .vscode/launch.json as well
+    '--inspect=6009',
+  ];
+
+  return {
+    // VS Code Insider launches extensions in debug mode by default but users
+    // install prod bundle so we have to check whether dev bundle exists.
+    module: debug && fs.existsSync(devBundle) ? devBundle : prodBundle,
+    transport: lsp.TransportKind.ipc,
+    args: constructArgs(ctx, debug),
+    options: {
+      env: debug ? devEnv : prodEnv,
+      execArgv: debug ? devExecArgv : prodExecArgv,
+    },
+  };
+}