Fix a timing issue for sequential importLibrary calls

#809

src/index.test.ts

@@ -425,6 +425,23 @@ test("importLibrary resolves correctly", async () => {
   expect(core).toEqual({ core: "fake" });
 });
 
+test("importLibrary resolves correctly without warning with sequential await", async () => {
+  console.warn = jest.fn();
+  window.google = { maps: {} } as any;
+  google.maps.importLibrary = async (name) => {
+    google.maps.version = "3.*.*";
+    return { [name]: "fake" } as any;
+  };
+
+  const loader = new Loader({ apiKey: "foo" });
+  const core = await loader.importLibrary("core");
+  const marker = await loader.importLibrary("marker");
+
+  expect(console.warn).toHaveBeenCalledTimes(0);
+  expect(core).toEqual({ core: "fake" });
+  expect(marker).toEqual({ marker: "fake" });
+});
+
 test("importLibrary can also set up bootstrap libraries (if bootstrap libraries empty)", async () => {
   const loader = new Loader({ apiKey: "foo" });
   loader.importLibrary("marker");

src/index.ts

@@ -623,26 +623,26 @@ export class Loader {
   private execute(): void {
     this.resetIfRetryingFailed();
 
+    if (this.loading) {
+      // do nothing but wait
+      return;
+    }
+
     if (this.done) {
       this.callback();
     } else {
       // short circuit and warn if google.maps is already loaded
       if (window.google && window.google.maps && window.google.maps.version) {
         console.warn(
-          "Google Maps already loaded outside @googlemaps/js-api-loader." +
+          "Google Maps already loaded outside @googlemaps/js-api-loader. " +
             "This may result in undesirable behavior as options and script parameters may not match."
         );
         this.callback();
         return;
       }
 
-      if (this.loading) {
-        // do nothing but wait
-      } else {
-        this.loading = true;
-
-        this.setScript();
-      }
+      this.loading = true;
+      this.setScript();
     }
   }
 }