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111 lines
3.8 KiB
JavaScript
111 lines
3.8 KiB
JavaScript
// deno-fmt-ignore-file
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// deno-lint-ignore-file
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// Copyright Joyent and Node contributors. All rights reserved. MIT license.
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// Taken from Node 18.12.1
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// This file is automatically generated by `tools/node_compat/setup.ts`. Do not modify this file manually.
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'use strict';
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const common = require('../common');
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// Ensure that subscribing the 'data' event will not make the stream flow.
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// The 'data' event will require calling read() by hand.
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//
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// The test is written for the (somewhat rare) highWaterMark: 0 streams to
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// specifically catch any regressions that might occur with these streams.
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const assert = require('assert');
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const { Readable } = require('stream');
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const streamData = [ 'a', null ];
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// Track the calls so we can assert their order later.
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const calls = [];
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const r = new Readable({
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read: common.mustCall(() => {
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calls.push('_read:' + streamData[0]);
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process.nextTick(() => {
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calls.push('push:' + streamData[0]);
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r.push(streamData.shift());
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});
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}, streamData.length),
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highWaterMark: 0,
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// Object mode is used here just for testing convenience. It really
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// shouldn't affect the order of events. Just the data and its format.
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objectMode: true,
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});
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assert.strictEqual(r.readableFlowing, null);
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r.on('readable', common.mustCall(() => {
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calls.push('readable');
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}, 2));
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assert.strictEqual(r.readableFlowing, false);
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r.on('data', common.mustCall((data) => {
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calls.push('data:' + data);
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}, 1));
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r.on('end', common.mustCall(() => {
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calls.push('end');
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}));
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assert.strictEqual(r.readableFlowing, false);
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// The stream emits the events asynchronously but that's not guaranteed to
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// happen on the next tick (especially since the _read implementation above
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// uses process.nextTick).
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//
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// We use setImmediate here to give the stream enough time to emit all the
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// events it's about to emit.
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setImmediate(() => {
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// Only the _read, push, readable calls have happened. No data must be
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// emitted yet.
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assert.deepStrictEqual(calls, ['_read:a', 'push:a', 'readable']);
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// Calling 'r.read()' should trigger the data event.
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assert.strictEqual(r.read(), 'a');
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assert.deepStrictEqual(
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calls,
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['_read:a', 'push:a', 'readable', 'data:a']);
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// The next 'read()' will return null because hwm: 0 does not buffer any
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// data and the _read implementation above does the push() asynchronously.
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//
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// Note: This 'null' signals "no data available". It isn't the end-of-stream
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// null value as the stream doesn't know yet that it is about to reach the
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// end.
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//
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// Using setImmediate again to give the stream enough time to emit all the
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// events it wants to emit.
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assert.strictEqual(r.read(), null);
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setImmediate(() => {
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// There's a new 'readable' event after the data has been pushed.
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// The 'end' event will be emitted only after a 'read()'.
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//
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// This is somewhat special for the case where the '_read' implementation
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// calls 'push' asynchronously. If 'push' was synchronous, the 'end' event
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// would be emitted here _before_ we call read().
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assert.deepStrictEqual(
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calls,
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['_read:a', 'push:a', 'readable', 'data:a',
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'_read:null', 'push:null', 'readable']);
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assert.strictEqual(r.read(), null);
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// While it isn't really specified whether the 'end' event should happen
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// synchronously with read() or not, we'll assert the current behavior
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// ('end' event happening on the next tick after read()) so any changes
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// to it are noted and acknowledged in the future.
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assert.deepStrictEqual(
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calls,
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['_read:a', 'push:a', 'readable', 'data:a',
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'_read:null', 'push:null', 'readable']);
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process.nextTick(() => {
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assert.deepStrictEqual(
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calls,
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['_read:a', 'push:a', 'readable', 'data:a',
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'_read:null', 'push:null', 'readable', 'end']);
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});
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});
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});
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