refactor(http): rework the HttpEvent union to improve narrowing. (#63267)

Prior to this change, `HttpProgressEvent` could not be narrowed to `HttpDownloadProgressEvent` or `HttpUploadProgressEvent`

PR Close #63267

Author: JeanMeche

goldens/public-api/common/http/index.api.md

@@ -2520,7 +2520,7 @@ export class HttpErrorResponse extends HttpResponseBase implements Error {
 }
 
 // @public
-export type HttpEvent<T> = HttpSentEvent | HttpHeaderResponse | HttpResponse<T> | HttpProgressEvent | HttpUserEvent<T>;
+export type HttpEvent<T> = HttpSentEvent | HttpHeaderResponse | HttpResponse<T> | HttpDownloadProgressEvent | HttpUploadProgressEvent | HttpUserEvent<T>;
 
 // @public
 export enum HttpEventType {

packages/common/http/src/response.ts

@@ -144,7 +144,8 @@ export type HttpEvent<T> =
   | HttpSentEvent
   | HttpHeaderResponse
   | HttpResponse<T>
-  | HttpProgressEvent
+  | HttpDownloadProgressEvent
+  | HttpUploadProgressEvent
   | HttpUserEvent<T>;
 
 /**

packages/common/http/test/response_spec.ts

@@ -7,7 +7,7 @@
  */
 
 import {HttpHeaders} from '../src/headers';
-import {HttpResponse, HttpStatusCode} from '../src/response';
+import {HttpEvent, HttpEventType, HttpResponse, HttpStatusCode} from '../src/response';
 
 describe('HttpResponse', () => {
   describe('constructor()', () => {
@@ -94,4 +94,18 @@ describe('HttpResponse', () => {
       expect(clone.redirected).toBe(false);
     });
   });
+
+  describe('typings', () => {
+    it('should correctly narrow based on the type', () => {
+      const httpEvent: HttpEvent<any> = {
+        type: HttpEventType.DownloadProgress,
+        loaded: 100,
+        total: 200,
+      };
+
+      if (httpEvent.type === HttpEventType.DownloadProgress) {
+        const partialText: string | undefined = httpEvent.partialText;
+      }
+    });
+  });
 });