1 files changed, 81 insertions, 0 deletions
diff --git a/cli/js/web/streams/readable_stream_async_iterator.ts b/cli/js/web/streams/readable_stream_async_iterator.ts
new file mode 100644
index 000000000..cd656e73d
--- /dev/null
+++ b/cli/js/web/streams/readable_stream_async_iterator.ts
@@ -0,0 +1,81 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+
+import * as sym from "./symbols.ts";
+import {
+  isReadableStreamAsyncIterator,
+  ReadableStreamAsyncIterator,
+  readableStreamCreateReadResult,
+  readableStreamReaderGenericCancel,
+  readableStreamReaderGenericRelease,
+  readableStreamDefaultReaderRead,
+} from "./internals.ts";
+import { assert } from "../../util.ts";
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+const AsyncIteratorPrototype: AsyncIterableIterator<any> = Object.getPrototypeOf(
+  Object.getPrototypeOf(async function* () {}).prototype
+);
+
+export const ReadableStreamAsyncIteratorPrototype: ReadableStreamAsyncIterator = Object.setPrototypeOf(
+  {
+    next(
+      this: ReadableStreamAsyncIterator
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    ): Promise<ReadableStreamReadResult<any>> {
+      if (!isReadableStreamAsyncIterator(this)) {
+        return Promise.reject(
+          new TypeError("invalid ReadableStreamAsyncIterator.")
+        );
+      }
+      const reader = this[sym.asyncIteratorReader];
+      if (!reader[sym.ownerReadableStream]) {
+        return Promise.reject(
+          new TypeError("reader owner ReadableStream is undefined.")
+        );
+      }
+      return readableStreamDefaultReaderRead(reader).then((result) => {
+        assert(typeof result === "object");
+        const { done } = result;
+        assert(typeof done === "boolean");
+        if (done) {
+          readableStreamReaderGenericRelease(reader);
+        }
+        const { value } = result;
+        return readableStreamCreateReadResult(value, done, true);
+      });
+    },
+    return(
+      this: ReadableStreamAsyncIterator,
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      value?: any | PromiseLike<any>
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+    ): Promise<ReadableStreamReadResult<any>> {
+      if (!isReadableStreamAsyncIterator(this)) {
+        return Promise.reject(
+          new TypeError("invalid ReadableStreamAsyncIterator.")
+        );
+      }
+      const reader = this[sym.asyncIteratorReader];
+      if (!reader[sym.ownerReadableStream]) {
+        return Promise.reject(
+          new TypeError("reader owner ReadableStream is undefined.")
+        );
+      }
+      if (reader[sym.readRequests].length) {
+        return Promise.reject(
+          new TypeError("reader has outstanding read requests.")
+        );
+      }
+      if (!this[sym.preventCancel]) {
+        const result = readableStreamReaderGenericCancel(reader, value);
+        readableStreamReaderGenericRelease(reader);
+        return result.then(() =>
+          readableStreamCreateReadResult(value, true, true)
+        );
+      }
+      readableStreamReaderGenericRelease(reader);
+      return Promise.resolve(readableStreamCreateReadResult(value, true, true));
+    },
+  },
+  AsyncIteratorPrototype
+);