Implement `ReadableStream.prototype[Symbol.asyncIterator]`

cc @fabiancook

2 files changed, 74 insertions, 0 deletions

diff --git a/src/bun.js/builtins/js/ReadableStream.js b/src/bun.js/builtins/js/ReadableStream.js
index 42c0fbdbc..8020b024d 100644
--- a/src/bun.js/builtins/js/ReadableStream.js
+++ b/src/bun.js/builtins/js/ReadableStream.js
@@ -443,3 +443,24 @@ function locked()
 
     return @isReadableStreamLocked(this);
 }
+
+function values(options) {
+    "use strict";
+    var prototype = this?.constructor?.prototype;
+    if (!prototype) {
+        return @undefined;
+    }
+    @readableStreamDefineLazyIterators(prototype);
+    return prototype.values.@call(this, options);
+}
+
+@linkTimeConstant
+function lazyAsyncIterator() {
+    "use strict";
+    var prototype = this?.constructor?.prototype;
+    if (!prototype) {
+        return @undefined;
+    }
+    @readableStreamDefineLazyIterators(prototype);
+    return prototype[globalThis.Symbol.asyncIterator].@call(this);
+}
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diff --git a/src/bun.js/builtins/js/ReadableStreamInternals.js b/src/bun.js/builtins/js/ReadableStreamInternals.js
index 5321ca922..cbe72c99e 100644
--- a/src/bun.js/builtins/js/ReadableStreamInternals.js
+++ b/src/bun.js/builtins/js/ReadableStreamInternals.js
@@ -2096,3 +2096,56 @@ async function readableStreamToArrayDirect(stream, underlyingSource) {
 
   return capability.@promise;
 }
+
+
+function readableStreamDefineLazyIterators(prototype) {
+    "use strict";
+
+    var asyncIterator = globalThis.Symbol.asyncIterator;
+
+    var ReadableStreamAsyncIterator = async function* ReadableStreamAsyncIterator(stream, preventCancel) {
+        var reader = stream.getReader();
+        var deferredError;
+          try {
+              while (true) {
+                  var done, value;
+                  const firstResult = reader.readMany();
+                  if (@isPromise(firstResult)) {
+                      const result = await firstResult;
+                      done = result.done;
+                      value = result.value;
+                  } else {
+                      done = firstResult.done;
+                      value = firstResult.value;
+                  }
+
+                  if (done) {
+                      return;
+                  }
+                  yield* value;
+              }
+          } catch(e) {
+            deferredError = e;
+          } finally {
+            reader.releaseLock();
+
+            if (!preventCancel) {
+                stream.cancel(deferredError);
+            }
+
+            if (deferredError) {
+            throw deferredError;
+          }
+          }
+    };
+
+    var createAsyncIterator = function asyncIterator() {
+        return ReadableStreamAsyncIterator(this, false);
+    };
+    var createValues = function values({preventCancel = false} = {preventCancel: false}) {
+        return ReadableStreamAsyncIterator(this, preventCancel);
+    };
+    @Object.@defineProperty(prototype, asyncIterator, { value: createAsyncIterator });
+    @Object.@defineProperty(prototype, "values", { value: createValues });
+    return prototype;
+}
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