- From: Jonas Sicking <jonas@sicking.cc>
- Date: Wed, 19 Feb 2014 12:11:36 -0800
- To: Boris Zbarsky <bzbarsky@mit.edu>
- Cc: "Mark S. Miller" <erights@google.com>, "public-script-coord@w3.org" <public-script-coord@w3.org>
On Wed, Feb 19, 2014 at 9:01 AM, Boris Zbarsky <bzbarsky@mit.edu> wrote: > For the record, the full set of > standards-track things (so excluding gecko-specific stuff) affected by that > change in Gecko is: > > 1) DedicatedWorkerGlobalScope.postMessage. Right now it requires > explicitly passing a message, but with the change you could pass undefined > by passing no arguments. > 2) IDBCursor.update. I think there are two separate questions here: "what behavior do we want" and "what WebIDL syntax should we use". I think agreement on the first question is needed before we can usefully debate the second question. Right now various objects have a `obj.postMessage(x)` method. The value of the first argument is what is sent as a message to the receiver. Do we want `obj.postMessage()` to send the value `undefined`? It seems a bit surprising to me that that doesn't throw an exception. The argument that we've used in the past for treating `undefined` as not-passed is to avoid people having to write code like: function func(optArg1, optArg2) { if (optArg1 === undefined) { otherFunc1(); } else { otherFunc1(optArg1); } if (optArg2 === undefined) { otherFunc2(); } else { otherFunc2(optArg2); } } and instead write function func(optArg1, optArg2) { otherFunc1(optArg1); otherFunc2(optArg2); } However the same argument doesn't seem to argue that `obj.postMessage()` should be treated as `obj.postMessage(undefined)`. I.e. you could still write function func(optArg1, optArg2) { obj.postMessage(optArg1); otherObj.postMessage(optArg2); } Also, I don't think we'll ever have the invariant that not-passed is always equivalent to `undefined` given functions like function func(args...) { return args.length; } So is it really intuitive that `postMessage()` sends the value `undefined`? Or that `cursor.update()` writes the value `undefined` to the database? All that said, if someone were to implement postMessage or cursor.update in JS rather than C++ the code would likely look something like function postMessage(data, otherArg) { verifyData(data); var s = serialize(data, otherArg); _receiver.acceptSerializedData(s); } which means that calling `postMessage()` would be equivalent to `postMessage(undefined)`. I.e. you could definitely argue that treating not-passed and `undefined` as equivalent would be more "javascripty". Interested in hearing others' thoughts. / Jonas
Received on Wednesday, 19 February 2014 20:12:34 UTC