@langgraph-js/sdk
Version:
The UI SDK for LangGraph - seamlessly integrate your AI agents with frontend interfaces
105 lines (104 loc) • 3.71 kB
JavaScript
/*
* Support async iterator syntax for ReadableStreams in all environments.
* Source: https://github.com/MattiasBuelens/web-streams-polyfill/pull/122#issuecomment-1627354490
*/
export class IterableReadableStream extends ReadableStream {
/** @ts-ignore */
reader;
ensureReader() {
if (!this.reader) {
this.reader = this.getReader();
}
}
async next() {
this.ensureReader();
try {
const result = await this.reader.read();
if (result.done) {
this.reader.releaseLock(); // release lock when stream becomes closed
return {
done: true,
value: undefined,
};
}
else {
return {
done: false,
value: result.value,
};
}
}
catch (e) {
this.reader.releaseLock(); // release lock when stream becomes errored
throw e;
}
}
async return() {
this.ensureReader();
// If wrapped in a Node stream, cancel is already called.
if (this.locked) {
const cancelPromise = this.reader.cancel(); // cancel first, but don't await yet
this.reader.releaseLock(); // release lock first
await cancelPromise; // now await it
}
return { done: true, value: undefined };
}
// eslint-disable-next-line @typescript-eslint/no-explicit-any
async throw(e) {
this.ensureReader();
if (this.locked) {
const cancelPromise = this.reader.cancel(); // cancel first, but don't await yet
this.reader.releaseLock(); // release lock first
await cancelPromise; // now await it
}
throw e;
}
// eslint-disable-next-line @typescript-eslint/ban-ts-comment
// @ts-ignore Not present in Node 18 types, required in latest Node 22
async [Symbol.asyncDispose]() {
await this.return();
}
[Symbol.asyncIterator]() {
return this;
}
static fromReadableStream(stream) {
// From https://developer.mozilla.org/en-US/docs/Web/API/Streams_API/Using_readable_streams#reading_the_stream
const reader = stream.getReader();
return new IterableReadableStream({
start(controller) {
return pump();
function pump() {
return reader.read().then(({ done, value }) => {
// When no more data needs to be consumed, close the stream
if (done) {
controller.close();
return;
}
// Enqueue the next data chunk into our target stream
controller.enqueue(value);
return pump();
});
}
},
cancel() {
reader.releaseLock();
},
});
}
static fromAsyncGenerator(generator) {
return new IterableReadableStream({
async pull(controller) {
const { value, done } = await generator.next();
// When no more data needs to be consumed, close the stream
if (done) {
controller.close();
}
// Fix: `else if (value)` will hang the streaming when nullish value (e.g. empty string) is pulled
controller.enqueue(value);
},
async cancel(reason) {
await generator.return(reason);
},
});
}
}