stream: fix enqueue race condition on esm modules

RafaelGSS · danielleadams · commit 9525b0d4928f · 2022-01-30T23:09:59.000-05:00
stream: use nextTick on close PR-URL: #40901 Reviewed-By: Robert Nagy <ronagy@icloud.com> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
diff --git a/lib/internal/webstreams/readablestream.js b/lib/internal/webstreams/readablestream.js
@@ -1431,13 +1431,18 @@ function readableStreamTee(stream, cloneForBranch2) {
         });
       },
       [kClose]() {
-        reading = false;
-        if (!canceled1)
-          readableStreamDefaultControllerClose(branch1[kState].controller);
-        if (!canceled2)
-          readableStreamDefaultControllerClose(branch2[kState].controller);
-        if (!canceled1 || !canceled2)
-          cancelPromise.resolve();
+        // The `process.nextTick()` is not part of the spec.
+        // This approach was needed to avoid a race condition working with esm
+        // Further information, see: https://github.com/nodejs/node/issues/39758
+        process.nextTick(() => {
+          reading = false;
+          if (!canceled1)
+            readableStreamDefaultControllerClose(branch1[kState].controller);
+          if (!canceled2)
+            readableStreamDefaultControllerClose(branch2[kState].controller);
+          if (!canceled1 || !canceled2)
+            cancelPromise.resolve();
+        });
       },
       [kError]() {
         reading = false;
diff --git a/test/parallel/test-whatwg-readablestream.mjs b/test/parallel/test-whatwg-readablestream.mjs
@@ -0,0 +1,36 @@
+import { mustCall } from '../common/index.mjs';
+import { ReadableStream } from 'stream/web';
+import assert from 'assert';
+
+{
+  // Test tee() with close in the nextTick after enqueue
+  async function read(stream) {
+    const chunks = [];
+    for await (const chunk of stream)
+      chunks.push(chunk);
+    return Buffer.concat(chunks).toString();
+  }
+
+  const [r1, r2] = new ReadableStream({
+    start(controller) {
+      process.nextTick(() => {
+        controller.enqueue(new Uint8Array([102, 111, 111, 98, 97, 114]));
+
+        process.nextTick(() => {
+          controller.close();
+        });
+      });
+    }
+  }).tee();
+
+  (async () => {
+    const [dataReader1, dataReader2] = await Promise.all([
+      read(r1),
+      read(r2),
+    ]);
+
+    assert.strictEqual(dataReader1, dataReader2);
+    assert.strictEqual(dataReader1, 'foobar');
+    assert.strictEqual(dataReader2, 'foobar');
+  })().then(mustCall());
+}
