mozilla-central/testing/web-platform/tests/streams/piping/then-interception.any.js (file symbol)

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// META: global=window,worker,shadowrealm
// META: script=../resources/test-utils.js
// META: script=../resources/recording-streams.js
'use strict';
function interceptThen() {
const intercepted = [];
let callCount = 0;
Object.prototype.then = function(resolver) {
if (!this.done) {
intercepted.push(this.value);
}
const retval = Object.create(null);
retval.done = ++callCount === 3;
retval.value = callCount;
resolver(retval);
if (retval.done) {
delete Object.prototype.then;
}
}
return intercepted;
}
promise_test(async t => {
const rs = new ReadableStream({
start(controller) {
controller.enqueue('a');
controller.close();
}
});
const ws = recordingWritableStream();
const intercepted = interceptThen();
t.add_cleanup(() => {
delete Object.prototype.then;
});
await rs.pipeTo(ws);
delete Object.prototype.then;
assert_array_equals(intercepted, [], 'nothing should have been intercepted');
assert_array_equals(ws.events, ['write', 'a', 'close'], 'written chunk should be "a"');
}, 'piping should not be observable');
promise_test(async t => {
const rs = new ReadableStream({
start(controller) {
controller.enqueue('a');
controller.close();
}
});
const ws = recordingWritableStream();
const [ branch1, branch2 ] = rs.tee();
const intercepted = interceptThen();
t.add_cleanup(() => {
delete Object.prototype.then;
});
await branch1.pipeTo(ws);
delete Object.prototype.then;
branch2.cancel();
assert_array_equals(intercepted, [], 'nothing should have been intercepted');
assert_array_equals(ws.events, ['write', 'a', 'close'], 'written chunk should be "a"');
}, 'tee should not be observable');