fix: Check language service is not already disabled

When making the check to determine if a project is Angular, it could be
the case that the language service is already disabled. This happens
when there are files in the project that exceeded limit.

This PR fixes the issue by first checking if the language service is
already disabled. Also added much more information to the logs to help
users diagnose the problem. Messages are logged to both remote console
(vscode) and file so that the former could inform users in their editor,
and the latter makes it much easier to correlate the sequence of events
in both TypeScript and Angular.

Related: #416

Author: Keen Yee Liau

server/src/session.ts

@@ -83,13 +83,9 @@ export class Session {
         break;
       case ts.server.ProjectLoadingFinishEvent: {
         const {project} = event.data;
-        if (!isAngularProject(project)) {
-          project.disableLanguageService();
-          this.connection.console.info(`Disabling language service for ${
-              project.projectName} because it is not an Angular project.`);
-        }
-        this.connection.sendNotification(
-            projectLoadingNotification.finish, event.data.project.projectName);
+        // Disable language service if project is not Angular
+        this.checkIsAngularProject(project);
+        this.connection.sendNotification(projectLoadingNotification.finish, project.projectName);
         break;
       }
       case ts.server.ProjectsUpdatedInBackgroundEvent:
@@ -378,19 +374,54 @@ export class Session {
   listen() {
     this.connection.listen();
   }
+
+  /**
+   * Determine if the specified `project` is Angular, and disable the language
+   * service if not.
+   * @param project
+   */
+  private checkIsAngularProject(project: ts.server.Project) {
+    const NG_CORE = '@angular/core/core.d.ts';
+    const {projectName} = project;
+    if (!project.languageServiceEnabled) {
+      const msg = `Language service is already disabled for ${projectName}. ` +
+          `This could be due to non-TS files that exceeded the size limit (${
+                      ts.server.maxProgramSizeForNonTsFiles} bytes).` +
+          `Please check log file for details.`;
+      this.connection.console.info(msg);  // log to remote console to inform users
+      project.log(msg);  // log to file, so that it's easier to correlate with ts entries
+      return;
+    }
+    if (!isAngularProject(project, NG_CORE)) {
+      project.disableLanguageService();
+      const totalFiles = project.getFileNames().length;
+      const msg =
+          `Disabling language service for ${projectName} because it is not an Angular project. ` +
+          `There are ${totalFiles} files in the project but '${NG_CORE}' is not detected.`;
+      this.connection.console.info(msg);
+      project.log(msg);
+      if (project.getExcludedFiles().some(f => f.endsWith(NG_CORE))) {
+        const msg =
+            `Please check your tsconfig.json to make sure 'node_modules' directory is not excluded.`;
+        this.connection.console.info(msg);
+        project.log(msg);
+      }
+    }
+  }
 }
 
 /**
  * Return true if the specified `project` contains the Angular core declaration.
  * @param project
+ * @param ngCore path that uniquely identifies `@angular/core`.
  */
-function isAngularProject(project: ts.server.Project): boolean {
+function isAngularProject(project: ts.server.Project, ngCore: string): boolean {
   project.markAsDirty();  // Must mark project as dirty to rebuild the program.
   if (project.isNonTsProject()) {
     return false;
   }
   for (const fileName of project.getFileNames()) {
-    if (fileName.endsWith('@angular/core/core.d.ts')) {
+    if (fileName.endsWith(ngCore)) {
       return true;
     }
   }