Merge pull request #67 from MattiasBuelens/fix-resolve-after-reject

Ignore resolving/rejecting promises after a previous resolve/reject
MattiasBuelens · Nov 12, 2020 · 65302aa · 65302aa
2 parents 0e2b4e2 + 094c3df
commit 65302aa
Show file tree

Hide file tree

Showing 4 changed files with 52 additions and 18 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -13,6 +13,7 @@
 
 * 📝 Add documentation to type definitions ([#62](https://github.com/MattiasBuelens/web-streams-polyfill/pull/62))
 * 👓 Align with [spec version `6cd5e81`](https://github.com/whatwg/streams/tree/6cd5e81f6191fed9e7d99ee73d4941e3060311ce/) ([#63](https://github.com/MattiasBuelens/web-streams-polyfill/pull/63))
+* 🐛 Fix an issue where the polyfill could throw an error when resolving/rejecting `reader.closed` when it was already resolved/rejected ([#66](https://github.com/MattiasBuelens/web-streams-polyfill/issues/66), [#67](https://github.com/MattiasBuelens/web-streams-polyfill/pull/67))
 
 ## v3.0.0 (2020-07-20)
 

diff --git a/src/lib/readable-stream/generic-reader.ts b/src/lib/readable-stream/generic-reader.ts
@@ -70,11 +70,12 @@ export function defaultReaderClosedPromiseInitializeAsResolved(reader: ReadableS
 }
 
 export function defaultReaderClosedPromiseReject(reader: ReadableStreamReader<any>, reason: any) {
-  assert(reader._closedPromise_resolve !== undefined);
-  assert(reader._closedPromise_reject !== undefined);
+  if (reader._closedPromise_reject === undefined) {
+    return;
+  }
 
   setPromiseIsHandledToTrue(reader._closedPromise);
-  reader._closedPromise_reject!(reason);
+  reader._closedPromise_reject(reason);
   reader._closedPromise_resolve = undefined;
   reader._closedPromise_reject = undefined;
 }
@@ -87,10 +88,11 @@ export function defaultReaderClosedPromiseResetToRejected(reader: ReadableStream
 }
 
 export function defaultReaderClosedPromiseResolve(reader: ReadableStreamReader<any>) {
-  assert(reader._closedPromise_resolve !== undefined);
-  assert(reader._closedPromise_reject !== undefined);
+  if (reader._closedPromise_resolve === undefined) {
+    return;
+  }
 
-  reader._closedPromise_resolve!(undefined);
+  reader._closedPromise_resolve(undefined);
   reader._closedPromise_resolve = undefined;
   reader._closedPromise_reject = undefined;
 }
diff --git a/src/lib/writable-stream.ts b/src/lib/writable-stream.ts
@@ -1266,12 +1266,13 @@ function defaultWriterClosedPromiseInitializeAsResolved(writer: WritableStreamDe
 }
 
 function defaultWriterClosedPromiseReject(writer: WritableStreamDefaultWriter, reason: any) {
-  assert(writer._closedPromise_resolve !== undefined);
-  assert(writer._closedPromise_reject !== undefined);
+  if (writer._closedPromise_reject === undefined) {
+    return;
+  }
   assert(writer._closedPromiseState === 'pending');
 
   setPromiseIsHandledToTrue(writer._closedPromise);
-  writer._closedPromise_reject!(reason);
+  writer._closedPromise_reject(reason);
   writer._closedPromise_resolve = undefined;
   writer._closedPromise_reject = undefined;
   writer._closedPromiseState = 'rejected';
@@ -1286,11 +1287,12 @@ function defaultWriterClosedPromiseResetToRejected(writer: WritableStreamDefault
 }
 
 function defaultWriterClosedPromiseResolve(writer: WritableStreamDefaultWriter) {
-  assert(writer._closedPromise_resolve !== undefined);
-  assert(writer._closedPromise_reject !== undefined);
+  if (writer._closedPromise_resolve === undefined) {
+    return;
+  }
   assert(writer._closedPromiseState === 'pending');
 
-  writer._closedPromise_resolve!(undefined);
+  writer._closedPromise_resolve(undefined);
   writer._closedPromise_resolve = undefined;
   writer._closedPromise_reject = undefined;
   writer._closedPromiseState = 'resolved';
@@ -1315,11 +1317,12 @@ function defaultWriterReadyPromiseInitializeAsResolved(writer: WritableStreamDef
 }
 
 function defaultWriterReadyPromiseReject(writer: WritableStreamDefaultWriter, reason: any) {
-  assert(writer._readyPromise_resolve !== undefined);
-  assert(writer._readyPromise_reject !== undefined);
+  if (writer._readyPromise_reject === undefined) {
+    return;
+  }
 
   setPromiseIsHandledToTrue(writer._readyPromise);
-  writer._readyPromise_reject!(reason);
+  writer._readyPromise_reject(reason);
   writer._readyPromise_resolve = undefined;
   writer._readyPromise_reject = undefined;
   writer._readyPromiseState = 'rejected';
@@ -1340,10 +1343,11 @@ function defaultWriterReadyPromiseResetToRejected(writer: WritableStreamDefaultW
 }
 
 function defaultWriterReadyPromiseResolve(writer: WritableStreamDefaultWriter) {
-  assert(writer._readyPromise_resolve !== undefined);
-  assert(writer._readyPromise_reject !== undefined);
+  if (writer._readyPromise_resolve === undefined) {
+    return;
+  }
 
-  writer._readyPromise_resolve!(undefined);
+  writer._readyPromise_resolve(undefined);
   writer._readyPromise_resolve = undefined;
   writer._readyPromise_reject = undefined;
   writer._readyPromiseState = 'fulfilled';

diff --git a/test/unit/readable-stream/regression.spec.js b/test/unit/readable-stream/regression.spec.js
@@ -0,0 +1,27 @@
+const { TransformStream } = require('../../../');
+
+describe('ReadableStream regressions', () => {
+  // https://github.com/MattiasBuelens/web-streams-polyfill/issues/66
+  it('#66', async () => {
+    const { readable, writable } = new TransformStream();
+
+    const producer = (async () => {
+      const writer = writable.getWriter();
+      await writer.write('hello');
+      // The async iterator releases its reader lock in the "close steps" of its pending read, which rejects the
+      // reader's closed promise. However, ReadableStreamClose then tries to resolve that same closed promise.
+      // This *should* be ignored (since the promise is already rejected), but instead would cause a TypeError.
+      await writer.close();
+    })();
+
+    const consumer = (async () => {
+      const results = [];
+      for await (const chunk of readable) {
+        results.push(chunk);
+      }
+      expect(results).toEqual(['hello']);
+    })();
+
+    await Promise.all([producer, consumer]);
+  });
+});