refactor(core): rename loader parameter to stream for rxResource (angular#60919)

As decided in the Resource RFC, this commit renames `loader` in `rxResource`
to `stream`. Some logic is left in to support gradual rollout of this change
in g3.

PR Close angular#60919

Author: alxhub

goldens/public-api/core/rxjs-interop/index.api.md

@@ -28,7 +28,7 @@ export function rxResource<T, R>(opts: RxResourceOptions<T, R>): ResourceRef<T |
 // @public
 export interface RxResourceOptions<T, R> extends BaseResourceOptions<T, R> {
     // (undocumented)
-    loader: (params: ResourceLoaderParams<R>) => Observable<T>;
+    stream: (params: ResourceLoaderParams<R>) => Observable<T>;
 }
 
 // @public

packages/core/rxjs-interop/src/rx_resource.ts

@@ -23,7 +23,7 @@ import {Observable, Subscription} from 'rxjs';
  * @experimental
  */
 export interface RxResourceOptions<T, R> extends BaseResourceOptions<T, R> {
-  loader: (params: ResourceLoaderParams<R>) => Observable<T>;
+  stream: (params: ResourceLoaderParams<R>) => Observable<T>;
 }
 
 /**
@@ -67,7 +67,13 @@ export function rxResource<T, R>(opts: RxResourceOptions<T, R>): ResourceRef<T |
         resolve = undefined;
       }
 
-      sub = opts.loader(params).subscribe({
+      // TODO(alxhub): remove after g3 updated to rename loader -> stream
+      const streamFn = opts.stream ?? (opts as {loader?: RxResourceOptions<T, R>['stream']}).loader;
+      if (streamFn === undefined) {
+        throw new Error(`Must provide \`stream\` option.`);
+      }
+
+      sub = streamFn(params).subscribe({
         next: (value) => send({value}),
         error: (error) => send({error}),
         complete: () => {

packages/core/rxjs-interop/test/rx_resource_spec.ts

@@ -16,7 +16,7 @@ describe('rxResource()', () => {
     const injector = TestBed.inject(Injector);
     const appRef = TestBed.inject(ApplicationRef);
     const res = rxResource({
-      loader: () => of(1),
+      stream: () => of(1),
       injector,
     });
     await appRef.whenStable();
@@ -31,7 +31,7 @@ describe('rxResource()', () => {
     let lastSeenRequest: number = 0;
     rxResource({
       params: request,
-      loader: ({params: request}) => {
+      stream: ({params: request}) => {
         lastSeenRequest = request;
         return new Observable((sub) => {
           if (request === 2) {
@@ -61,7 +61,7 @@ describe('rxResource()', () => {
     const appRef = TestBed.inject(ApplicationRef);
     const response = new BehaviorSubject(1);
     const res = rxResource({
-      loader: () => response,
+      stream: () => response,
       injector,
     });
     await appRef.whenStable();