fix(language-server): Ensure LS is enabled in same order as project initialization (#1447)

ngcc processes might finish out of order, but we need to re-enable the language service for
the projects in the same order that the ngcc processes were spawned in. With solution-style
configs, we need to ensure that the language service enabling respects the order that the
projects were defined in the references list. If we enable the language service out of order,
the second project in the list will request diagnostics first and then be the project that's
prioritized for that project's set of files. This will cause issues if the second project is,
for example, one that only includes `*.spec.ts` files and not the entire set of files needed
to compile the app (i.e. `*.module.ts`).

A test was not written for this because it is difficult to consistently emulate the
`ngcc` processes finishing out of order with solution style project configs.

Fixes #1444

Author: atscott

server/src/session.ts

@@ -53,6 +53,9 @@ export class Session {
   private readonly configuredProjToExternalProj = new Map<string, string>();
   private readonly logToConsole: boolean;
   private readonly openFiles = new MruTracker();
+  // Tracks the spawn order and status of the `ngcc` processes. This allows us to ensure we enable
+  // the LS in the same order the projects were created in.
+  private projectNgccQueue: Array<{project: ts.server.Project, done: boolean}> = [];
   private diagnosticsTimeout: NodeJS.Timeout|null = null;
   private isProjectLoading = false;
   /**
@@ -1098,6 +1101,7 @@ export class Session {
     let success = false;
 
     try {
+      this.projectNgccQueue.push({project, done: false});
       await resolveAndRunNgcc(configFilePath, {
         report: (msg: string) => {
           this.connection.sendProgress(NgccProgressType, NgccProgressToken, {
@@ -1114,19 +1118,34 @@ export class Session {
               configFilePath}, language service may not operate correctly:\n` +
           `    ${e.message}`);
     } finally {
+      const loadingStatus = this.projectNgccQueue.find(p => p.project === project);
+      if (loadingStatus !== undefined) {
+        loadingStatus.done = true;
+      }
       this.connection.sendProgress(NgccProgressType, NgccProgressToken, {
         done: true,
         configFilePath,
         success,
       });
     }
 
-    // Re-enable language service even if ngcc fails, because users could fix
-    // the problem by running ngcc themselves. If we keep language service
-    // disabled, there's no way users could use the extension even after
-    // resolving ngcc issues. On the client side, we will warn users about
-    // potentially degraded experience.
-    this.enableLanguageServiceForProject(project);
+    // ngcc processes might finish out of order, but we need to re-enable the language service for
+    // the projects in the same order that the ngcc processes were spawned in. With solution-style
+    // configs, we need to ensure that the language service enabling respects the order that the
+    // projects were defined in the references list. If we enable the language service out of order,
+    // the second project in the list will request diagnostics first and then be the project that's
+    // prioritized for that project's set of files. This will cause issues if the second project is,
+    // for example, one that only includes `*.spec.ts` files and not the entire set of files needed
+    // to compile the app (i.e. `*.module.ts`).
+    for (let i = 0; i < this.projectNgccQueue.length && this.projectNgccQueue[i].done; i++) {
+      // Re-enable language service even if ngcc fails, because users could fix
+      // the problem by running ngcc themselves. If we keep language service
+      // disabled, there's no way users could use the extension even after
+      // resolving ngcc issues. On the client side, we will warn users about
+      // potentially degraded experience.
+      this.enableLanguageServiceForProject(this.projectNgccQueue[i].project);
+    }
+    this.projectNgccQueue = this.projectNgccQueue.filter(({done}) => !done);
   }
 }