stream: utility consumers for web and node.js streams

doc/api/webstreams.md

@@ -1270,5 +1270,78 @@ added: REPLACEME
 
 * Type: {WritableStream}
 
+### Utility Consumers
+<!-- YAML
+added: REPLACEME
+-->
+
+The utility consumer functions provide common options for consuming
+streams.
+
+They are accessed using:
+
+```mjs
+import {
+  arrayBuffer,
+  blob,
+  json,
+  text,
+} from 'node:stream/consumers';
+```
+
+```cjs
+const {
+  arrayBuffer,
+  blob,
+  json,
+  text,
+} = require('stream/consumers');
+```
+
+#### `streamConsumers.arrayBuffer(stream)`
+<!-- YAML
+added: REPLACEME
+-->
+
+* `stream` {ReadableStream|stream.Readable|AsyncIterator}
+* Returns: {Promise} Fulfills with an `ArrayBuffer` containing the full
+  contents of the stream.
+
+#### `streamConsumers.blob(stream)`
+<!-- YAML
+added: REPLACEME
+-->
+
+* `stream` {ReadableStream|stream.Readable|AsyncIterator}
+* Returns: {Promise} Fulfills with a {Blob} containing the full contents
+  of the stream.
+
+#### `streamConsumers.buffer(stream)`
+<!-- YAML
+added: REPLACEME
+-->
+
+* `stream` {ReadableStream|stream.Readable|AsyncIterator}
+* Returns: {Promise} Fulfills with a {Buffer} containing the full
+  contents of the stream.
+
+#### `streamConsumers.json(stream)`
+<!-- YAML
+added: REPLACEME
+-->
+
+* `stream` {ReadableStream|stream.Readable|AsyncIterator}
+* Returns: {Promise} Fulfills with the contents of the stream parsed as a
+  UTF-8 encoded string that is then passed through `JSON.parse()`.
+
+#### `streamConsumers.text(stream)`
+<!-- YAML
+added: REPLACEME
+-->
+
+* `stream` {ReadableStream|stream.Readable|AsyncIterator}
+* Returns: {Promise} Fulfills with the contents of the stream parsed as a
+  UTF-8 encoded string.
+
 [Streams]: stream.md
 [WHATWG Streams Standard]: https://streams.spec.whatwg.org/

lib/stream/consumers.js

@@ -0,0 +1,84 @@
+'use strict';
+
+const {
+  JSONParse,
+} = primordials;
+
+const {
+  TextDecoder,
+} = require('internal/encoding');
+
+const {
+  Blob,
+} = require('internal/blob');
+
+const {
+  Buffer,
+} = require('buffer');
+
+/**
+ * @typedef {import('../internal/webstreams/readablestream').ReadableStream
+ * } ReadableStream
+ * @typedef {import('../internal/streams/readable')} Readable
+ */
+
+/**
+ * @param {AsyncIterable|ReadableStream|Readable} stream
+ * @returns {Promise<Blob>}
+ */
+async function blob(stream) {
+  const chunks = [];
+  for await (const chunk of stream)
+    chunks.push(chunk);
+  return new Blob(chunks);
+}
+
+/**
+ * @param {AsyncIterable|ReadableStream|Readable} stream
+ * @returns {Promise<ArrayBuffer>}
+ */
+async function arrayBuffer(stream) {
+  const ret = await blob(stream);
+  return ret.arrayBuffer();
+}
+
+/**
+ * @param {AsyncIterable|ReadableStream|Readable} stream
+ * @returns {Promise<Buffer>}
+ */
+async function buffer(stream) {
+  return Buffer.from(await arrayBuffer(stream));
+}
+
+/**
+ * @param {AsyncIterable|ReadableStream|Readable} stream
+ * @returns {Promise<string>}
+ */
+async function text(stream) {
+  const dec = new TextDecoder();
+  let str = '';
+  for await (const chunk of stream) {
+    if (typeof chunk === 'string')
+      str += chunk;
+    else
+      str += dec.decode(chunk, { stream: true });
+  }
+  return str;
+}
+
+/**
+ * @param {AsyncIterable|ReadableStream|Readable} stream
+ * @returns {Promise<any>}
+ */
+async function json(stream) {
+  const str = await text(stream);
+  return JSONParse(str);
+}
+
+module.exports = {
+  arrayBuffer,
+  blob,
+  buffer,
+  text,
+  json,
+};

test/parallel/test-stream-consumers.js

@@ -0,0 +1,234 @@
+// Flags: --no-warnings
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+
+const {
+  arrayBuffer,
+  blob,
+  buffer,
+  text,
+  json,
+} = require('stream/consumers');
+
+const {
+  PassThrough
+} = require('stream');
+
+const {
+  TransformStream,
+} = require('stream/web');
+
+const buf = Buffer.from('hellothere');
+const kArrayBuffer =
+  buf.buffer.slice(buf.byteOffset, buf.byteOffset + buf.byteLength);
+
+{
+  const passthrough = new PassThrough();
+
+  blob(passthrough).then(common.mustCall(async (blob) => {
+    assert.strictEqual(blob.size, 10);
+    assert.deepStrictEqual(await blob.arrayBuffer(), kArrayBuffer);
+  }));
+
+  passthrough.write('hello');
+  setTimeout(() => passthrough.end('there'), 10);
+}
+
+{
+  const passthrough = new PassThrough();
+
+  arrayBuffer(passthrough).then(common.mustCall(async (ab) => {
+    assert.strictEqual(ab.byteLength, 10);
+    assert.deepStrictEqual(ab, kArrayBuffer);
+  }));
+
+  passthrough.write('hello');
+  setTimeout(() => passthrough.end('there'), 10);
+}
+
+{
+  const passthrough = new PassThrough();
+
+  buffer(passthrough).then(common.mustCall(async (buf) => {
+    assert.strictEqual(buf.byteLength, 10);
+    assert.deepStrictEqual(buf.buffer, kArrayBuffer);
+  }));
+
+  passthrough.write('hello');
+  setTimeout(() => passthrough.end('there'), 10);
+}
+
+
+{
+  const passthrough = new PassThrough();
+
+  text(passthrough).then(common.mustCall(async (str) => {
+    assert.strictEqual(str.length, 10);
+    assert.deepStrictEqual(str, 'hellothere');
+  }));
+
+  passthrough.write('hello');
+  setTimeout(() => passthrough.end('there'), 10);
+}
+
+{
+  const passthrough = new PassThrough();
+
+  json(passthrough).then(common.mustCall(async (str) => {
+    assert.strictEqual(str.length, 10);
+    assert.deepStrictEqual(str, 'hellothere');
+  }));
+
+  passthrough.write('"hello');
+  setTimeout(() => passthrough.end('there"'), 10);
+}
+
+{
+  const { writable, readable } = new TransformStream();
+
+  blob(readable).then(common.mustCall(async (blob) => {
+    assert.strictEqual(blob.size, 10);
+    assert.deepStrictEqual(await blob.arrayBuffer(), kArrayBuffer);
+  }));
+
+  const writer = writable.getWriter();
+  writer.write('hello');
+  setTimeout(() => {
+    writer.write('there');
+    writer.close();
+  }, 10);
+
+  assert.rejects(blob(readable), { code: 'ERR_INVALID_STATE' });
+}
+
+{
+  const { writable, readable } = new TransformStream();
+
+  arrayBuffer(readable).then(common.mustCall(async (ab) => {
+    assert.strictEqual(ab.byteLength, 10);
+    assert.deepStrictEqual(ab, kArrayBuffer);
+  }));
+
+  const writer = writable.getWriter();
+  writer.write('hello');
+  setTimeout(() => {
+    writer.write('there');
+    writer.close();
+  }, 10);
+
+  assert.rejects(arrayBuffer(readable), { code: 'ERR_INVALID_STATE' });
+}
+
+{
+  const { writable, readable } = new TransformStream();
+
+  text(readable).then(common.mustCall(async (str) => {
+    assert.strictEqual(str.length, 10);
+    assert.deepStrictEqual(str, 'hellothere');
+  }));
+
+  const writer = writable.getWriter();
+  writer.write('hello');
+  setTimeout(() => {
+    writer.write('there');
+    writer.close();
+  }, 10);
+
+  assert.rejects(text(readable), { code: 'ERR_INVALID_STATE' });
+}
+
+{
+  const { writable, readable } = new TransformStream();
+
+  json(readable).then(common.mustCall(async (str) => {
+    assert.strictEqual(str.length, 10);
+    assert.deepStrictEqual(str, 'hellothere');
+  }));
+
+  const writer = writable.getWriter();
+  writer.write('"hello');
+  setTimeout(() => {
+    writer.write('there"');
+    writer.close();
+  }, 10);
+
+  assert.rejects(json(readable), { code: 'ERR_INVALID_STATE' });
+}
+
+{
+  const stream = new PassThrough({
+    readableObjectMode: true,
+    writableObjectMode: true,
+  });
+
+  blob(stream).then(common.mustCall((blob) => {
+    assert.strictEqual(blob.size, 30);
+  }));
+
+  stream.write({});
+  stream.end({});
+}
+
+{
+  const stream = new PassThrough({
+    readableObjectMode: true,
+    writableObjectMode: true,
+  });
+
+  arrayBuffer(stream).then(common.mustCall((ab) => {
+    assert.strictEqual(ab.byteLength, 30);
+    assert.strictEqual(
+      Buffer.from(ab).toString(),
+      '[object Object][object Object]');
+  }));
+
+  stream.write({});
+  stream.end({});
+}
+
+{
+  const stream = new PassThrough({
+    readableObjectMode: true,
+    writableObjectMode: true,
+  });
+
+  buffer(stream).then(common.mustCall((buf) => {
+    assert.strictEqual(buf.byteLength, 30);
+    assert.strictEqual(
+      buf.toString(),
+      '[object Object][object Object]');
+  }));
+
+  stream.write({});
+  stream.end({});
+}
+
+{
+  const stream = new PassThrough({
+    readableObjectMode: true,
+    writableObjectMode: true,
+  });
+
+  assert.rejects(text(stream), {
+    code: 'ERR_INVALID_ARG_TYPE',
+  });
+
+  stream.write({});
+  stream.end({});
+}
+
+{
+  const stream = new PassThrough({
+    readableObjectMode: true,
+    writableObjectMode: true,
+  });
+
+  assert.rejects(json(stream), {
+    code: 'ERR_INVALID_ARG_TYPE',
+  });
+
+  stream.write({});
+  stream.end({});
+}