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worker: add typechecking for postMessage transfer list #28033

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worker: add typechecking for postMessage transfer list #28033

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7580ecb
worker: add typechecking for postMessage transfer list
addaleax Jun 2, 2019
5c9f1c6
fixup! worker: add typechecking for postMessage transfer list
addaleax Jun 9, 2019
8aac5b2
fixup! worker: add typechecking for postMessage transfer list
addaleax Jun 9, 2019
ace5dff
fixup! worker: add typechecking for postMessage transfer list
addaleax Jun 9, 2019
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7 changes: 7 additions & 0 deletions src/node_messaging.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -711,6 +711,13 @@ void MessagePort::PostMessage(const FunctionCallbackInfo<Value>& args) {
return THROW_ERR_MISSING_ARGS(env, "Not enough arguments to "
"MessagePort.postMessage");
}
if (!args[1]->IsNullOrUndefined() && !args[1]->IsObject()) {
// Browsers also do not throw on `null` or objects, although it really
// should be an array or undefined, thus the mismatch between the checks
// above and the actual error message.
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The reason for this is due to the fact that browsers have an overload that accepts an option bag in addition to just a transfer list. See https://html.spec.whatwg.org/multipage/web-messaging.html#messageport. How browsers resolve the overloading is roughly something like this

  1. If second arg is undefined or null then ignore.
  2. If second arg is not an object (i.e., also not a function), then throw.
  3. Try to get the Symbol.iterator property of the second arg.
    1. If that throws, then rethrow the exception.
    2. If that returns anything other than undefined or function, also throw an exception.
    3. If it returns a function, then treat this as an iterable and use the equivalent of Array.from to convert it to a list.
    4. Otherwise (it returns undefined), then treat the second arg as an option bag. Try to get the transferList property and then convert it to a list through something like Array.from if present.

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@TimothyGu I’m adding a TODO comment in this PR and merge this with the current state, if that’s okay with you

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@TimothyGu TimothyGu Jun 10, 2019 •
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Yeah sure. You might encounter it as we try to pass more WPTs, so hope it'd be helpful.

return THROW_ERR_INVALID_ARG_TYPE(env,
"Optional transferList argument must be an array");
}

MessagePort* port = Unwrap<MessagePort>(args.This());
// Even if the backing MessagePort object has already been deleted, we still
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20 changes: 20 additions & 0 deletions test/parallel/test-worker-message-port.js
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Expand Up @@ -70,6 +70,26 @@ const { MessageChannel, MessagePort } = require('worker_threads');
});
}

{
const { port1, port2 } = new MessageChannel();
port2.on('message', common.mustCall(4));
port1.postMessage(1, null);
port1.postMessage(2, undefined);
port1.postMessage(3, []);
port1.postMessage(4, {});

const err = {
constructor: TypeError,
code: 'ERR_INVALID_ARG_TYPE',
message: 'Transfer list argument must be array or missing'
};

assert.throws(() => port1.postMessage(5, 0), err);
assert.throws(() => port1.postMessage(5, false), err);
assert.throws(() => port1.postMessage(5, 'X'), err);
assert.throws(() => port1.postMessage(5, Symbol('X')), err);
}

{
assert.deepStrictEqual(
Object.getOwnPropertyNames(MessagePort.prototype).sort(),
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