Implement emberjs/rfcs#1065

Author: NullVoxPopuli

addon/src/index.ts

@@ -20,3 +20,4 @@ export {
 export { default as buildWaiter, _resetWaiterNames } from './build-waiter.ts';
 export { default as waitForPromise } from './wait-for-promise.ts';
 export { default as waitFor } from './wait-for.ts';
+export { waitForFetch } from './wait-for-fetch.ts';

addon/src/wait-for-fetch.ts

@@ -0,0 +1,27 @@
+import { default as waitForPromise } from './wait-for-promise';
+
+export async function waitForFetch(fetchPromise: ReturnType<typeof fetch>) {
+  // eslint-disable-next-line @typescript-eslint/no-floating-promises
+  waitForPromise(fetchPromise);
+
+  const response = await fetchPromise;
+
+  return new Proxy(response, {
+    get(target, prop, receiver) {
+      const original = Reflect.get(target, prop, receiver);
+
+      if (
+        typeof prop === 'string' &&
+        ['json', 'text', 'arrayBuffer', 'blob', 'formData'].includes(prop)
+      ) {
+        return (...args: unknown[]) => {
+          const parsePromise = original.call(target, ...args);
+
+          return waitForPromise(parsePromise);
+        };
+      }
+
+      return original;
+    },
+  });
+}