fix(aio): emit a hard-coded doc if file-not-found fails

Closes #14848

aio/src/app/documents/document.service.spec.ts

@@ -78,7 +78,31 @@ describe('DocumentService', () => {
     });
 
     it('should emit the not-found document if the document is not found on the server', () => {
+      const { service, backend } = getServices('missing/url');
+      const connections = backend.connectionsArray;
+      service.currentDocument.subscribe();
 
+      connections[0].mockError(new Response(new ResponseOptions({ status: 404, statusText: 'NOT FOUND'})) as any);
+      expect(connections.length).toEqual(2);
+      expect(connections[1].request.url).toEqual(CONTENT_URL_PREFIX + 'file-not-found.json');
+    });
+
+    it('should emit a hard-coded not-found document if the not-found document is not found on the server', () => {
+      let currentDocument: DocumentContents;
+      const notFoundDoc = { title: 'Not Found', contents: 'Document not found' };
+      const nextDoc = { title: 'Next Doc' };
+      const { service, backend, location } = getServices('file-not-found');
+      const connections = backend.connectionsArray;
+      service.currentDocument.subscribe(doc => currentDocument = doc);
+
+      connections[0].mockError(new Response(new ResponseOptions({ status: 404, statusText: 'NOT FOUND'})) as any);
+      expect(connections.length).toEqual(1);
+      expect(currentDocument).toEqual(notFoundDoc);
+
+      // now check that we haven't killed the currentDocument observable sequence
+      location.urlSubject.next('new/url');
+      connections[1].mockRespond(createResponse(nextDoc));
+      expect(currentDocument).toEqual(nextDoc);
     });
 
     it('should not make a request to the server if the doc is in the cache already', () => {

aio/src/app/documents/document.service.ts

@@ -8,7 +8,7 @@ import 'rxjs/add/operator/switchMap';
 import { LocationService } from 'app/shared/location.service';
 import { Logger } from 'app/shared/logger.service';
 
-const FILE_NOT_FOUND_DOC = 'file-not-found';
+const FILE_NOT_FOUND_URL = 'file-not-found';
 
 export interface DocumentContents {
   title: string;
@@ -19,6 +19,7 @@ export interface DocumentContents {
 export class DocumentService {
 
   private cache = new Map<string, Observable<DocumentContents>>();
+  private fileNotFoundPath = this.computePath(FILE_NOT_FOUND_URL);
 
   currentDocument: Observable<DocumentContents>;
 
@@ -43,10 +44,14 @@ export class DocumentService {
       .get(path)
       .map(res => res.json())
       .catch((error: Response) => {
-        if (error.status === 404 && path !== FILE_NOT_FOUND_DOC) {
-          this.logger.error(`Document file not found at '${path}'`);
-          // using `getDocument` means that we can fetch the 404 doc contents from the server and cache it
-          return this.getDocument(FILE_NOT_FOUND_DOC);
+        if (error.status === 404) {
+          if (path !== this.fileNotFoundPath) {
+            this.logger.error(`Document file not found at '${path}'`);
+            // using `getDocument` means that we can fetch the 404 doc contents from the server and cache it
+            return this.getDocument(FILE_NOT_FOUND_URL);
+          } else {
+            return Observable.of({ title: 'Not Found', contents: 'Document not found' });
+          }
         } else {
           throw error;
         }