refactor: remove legacy code for IE in ajax

BREAKING CHANGE: `ajax` no longer supports IE

Author: demensky

spec/observables/dom/ajax-spec.ts

@@ -330,37 +330,6 @@ describe('ajax', () => {
     expect(complete).to.be.true;
   });
 
-  it('should fail if fails to parse response in older IE', () => {
-    let error: any;
-    const obj: AjaxConfig = {
-      url: '/flibbertyJibbet',
-      method: '',
-    };
-
-    // No `response` property on the object (for older IE).
-    MockXMLHttpRequest.noResponseProp = true;
-
-    ajax(obj).subscribe({
-      next: () => {
-        throw new Error('should not next');
-      },
-      error: (err: any) => {
-        error = err;
-      },
-      complete: () => {
-        throw new Error('should not complete');
-      },
-    });
-
-    MockXMLHttpRequest.mostRecent.respondWith({
-      status: 207,
-      responseText: 'Wee! I am text, but should be valid JSON!',
-    });
-
-    expect(error instanceof SyntaxError).to.be.true;
-    expect(error.message).to.equal('Unexpected token W in JSON at position 0');
-  });
-
   it('should fail on 404', () => {
     let error: any;
     const obj: AjaxConfig = {
@@ -1583,11 +1552,6 @@ class MockXHREventTarget {
 class MockXMLHttpRequest extends MockXHREventTarget {
   static readonly DONE = 4;
 
-  /**
-   * Set to `true` to test IE code paths.
-   */
-  static noResponseProp = false;
-
   private static requests: Array<MockXMLHttpRequest> = [];
   private static recentRequest: MockXMLHttpRequest;
 
@@ -1600,7 +1564,6 @@ class MockXMLHttpRequest extends MockXHREventTarget {
   }
 
   static clearRequest(): void {
-    MockXMLHttpRequest.noResponseProp = false;
     MockXMLHttpRequest.requests.length = 0;
     MockXMLHttpRequest.recentRequest = null!;
   }
@@ -1639,9 +1602,6 @@ class MockXMLHttpRequest extends MockXHREventTarget {
     super();
     MockXMLHttpRequest.recentRequest = this;
     MockXMLHttpRequest.requests.push(this);
-    if (MockXMLHttpRequest.noResponseProp) {
-      delete this['response'];
-    }
   }
 
   // @ts-ignore: Property has no initializer and is not definitely assigned
@@ -1755,11 +1715,6 @@ class MockXMLHttpRequest extends MockXHREventTarget {
         break;
     }
 
-    // We're testing old IE, forget all of that response property stuff.
-    if (MockXMLHttpRequest.noResponseProp) {
-      delete this['response'];
-    }
-
     this.triggerEvent('load', { type: 'load', total: response.total ?? 0, loaded: response.loaded ?? 0 });
     this.triggerEvent('readystatechange', { type: 'readystatechange' });
   }

src/internal/ajax/ajax.ts

@@ -481,18 +481,7 @@ export function fromAjax<T>(init: AjaxConfig): Observable<AjaxResponse<T>> {
         if (status < 400) {
           progressSubscriber?.complete?.();
 
-          let response: AjaxResponse<T>;
-          try {
-            // This can throw in IE, because we end up needing to do a JSON.parse
-            // of the response in some cases to produce object we'd expect from
-            // modern browsers.
-            response = createResponse(DOWNLOAD, event);
-          } catch (err) {
-            destination.error(err);
-            return;
-          }
-
-          destination.next(response);
+          destination.next(createResponse(DOWNLOAD, event));
           destination.complete();
         } else {
           progressSubscriber?.error?.(event);

src/internal/ajax/errors.ts

@@ -63,15 +63,7 @@ export const AjaxError: AjaxErrorCtor = createErrorClass(
       this.request = request;
       this.status = xhr.status;
       this.responseType = xhr.responseType;
-      let response: any;
-      try {
-        // This can throw in IE, because we have to do a JSON.parse of
-        // the response in some cases to get the expected response property.
-        response = getXHRResponse(xhr);
-      } catch (err) {
-        response = xhr.responseText;
-      }
-      this.response = response;
+      this.response = getXHRResponse(xhr);
     }
 );
 

src/internal/ajax/getXHRResponse.ts

@@ -1,37 +1,11 @@
 /**
- * Gets what should be in the `response` property of the XHR. However,
- * since we still support the final versions of IE, we need to do a little
- * checking here to make sure that we get the right thing back. Consequently,
- * we need to do a JSON.parse() in here, which *could* throw if the response
- * isn't valid JSON.
+ * Gets what should be in the `response` property of the XHR.
  *
  * This is used both in creating an AjaxResponse, and in creating certain errors
  * that we throw, so we can give the user whatever was in the response property.
  *
  * @param xhr The XHR to examine the response of
  */
 export function getXHRResponse(xhr: XMLHttpRequest) {
-  switch (xhr.responseType) {
-    case 'json': {
-      if ('response' in xhr) {
-        return xhr.response;
-      } else {
-        // IE
-        const ieXHR: any = xhr;
-        return JSON.parse(ieXHR.responseText);
-      }
-    }
-    case 'document':
-      return xhr.responseXML;
-    case 'text':
-    default: {
-      if ('response' in xhr) {
-        return xhr.response;
-      } else {
-        // IE
-        const ieXHR: any = xhr;
-        return ieXHR.responseText;
-      }
-    }
-  }
+  return xhr.responseType === 'document' ? xhr.responseXML : xhr.response;
 }