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Re: QSA, the problem with ":scope", and naming

From: Alex Russell <slightlyoff@google.com>
Date: Wed, 19 Oct 2011 01:03:08 +0100
Message-ID: <CANr5HFUygBq=LSxhqgS9Jho+hvLzob_fNGxK1NxzsMePNtMWfQ@mail.gmail.com>
To: Brian Kardell <bkardell@gmail.com>
Cc: Webapps WG <public-webapps@w3.org>, Yehuda Katz <wycats@gmail.com>, John Resig <jeresig@gmail.com>, Paul Irish <paulirish@google.com>, Lachlan Hunt <lachlan.hunt@lachy.id.au>
On Tue, Oct 18, 2011 at 8:59 PM, Brian Kardell <bkardell@gmail.com> wrote:
> I know that there were discussions that crossed over into CSS about a
> @global or a :context which could sort of include things outside the
> scope as part of the query but not be the subject.  Does any of that
> relate here?

I suppose it does, but only as an implementation detail. Nothing more
than the ID prefix hack or ":scope" are really necessary to get the
API we need.

> PS
>> Out come the knives! You can't start a selector with a combinator!
> Even on CSS lists this has been proposed inside of pseudos... Numerous
> times and in numerous contexts.   It seems to me that everyone (even
> the people who disagree with the proposal) knows what it means
> immediately - but you are right... That's always the response.  So at
> the risk of being stabbed by an angry mob:  Can someone explain _why_
> you can't - under absolutely any circumstances - begin a selector with
> a combinator - even if there appears to be wide agreement that it
> makes sense in a finite set of circumstances?
> On Tue, Oct 18, 2011 at 12:42 PM, Alex Russell <slightlyoff@google.com> wrote:
>> Lachlan and I have been having an...um...*spirited* twitter discussion
>> regarding querySelectorAll, the (deceased?) queryScopedSelectorAll,
>> and ":scope". He asked me to continue here, so I'll try to keep it
>> short:
>> The rooted forms of "querySelector" and "querySelectorAll" are mis-designed.
>> Discussions about a Scoped variant or ":scope" pseudo tacitly
>> acknowledge this, and the JS libraries are proof in their own right:
>> no major JS library exposes the QSA semantic, instead choosing to
>> implement a rooted search.
>> Related and equally important, that querySelector and querySelectorAll
>> are often referred to by the abbreviation "QSA" suggests that its name
>> is bloated and improved versions should have shorter names. APIs gain
>> use both through naming and through use. On today's internet -- the
>> one where 50% of all websites include jQuery -- you could even go with
>> element.$("selector") and everyone would know what you mean: it's
>> clearly a search rooted at the element on the left-hand side of the
>> dot.
>> Ceteris peribus, shorter is better. When there's a tie that needs to
>> be broken, the more frequently used the API, the shorter the name it
>> deserves -- i.e., the larger the component of its meaning it will gain
>> through use and repetition and not naming and documentation.
>> I know some on this list might disagree, but all of the above is
>> incredibly non-controversial today. Even if there may have been
>> debates about scoping or naming when QSA was originally designed,
>> history has settled them. And QSA lost on both counts.
>> I therefore believe that this group's current design for scoped
>> selection could be improved significantly. If I understand the latest
>> draft (http://www.w3.org/TR/selectors-api2/#the-scope-pseudo-class)
>> correctly, a scoped search for multiple elements would be written as:
>>   element.querySelectorAll(":scope > div > .thinger");
>> Both then name and the need to specify ":scope" are punitive to
>> readers and writers of this code. The selector is *obviously*
>> happening in relationship to "element" somehow. The only sane
>> relationship (from a modern JS hacker's perspective) is that it's
>> where our selector starts from. I'd like to instead propose that we
>> shorten all of this up and kill both stones by introducing a new API
>> pair, "find" and "findAll", that are rooted as JS devs expect. The
>> above becomes:
>>   element.findAll("> div > .thinger");
>> Out come the knives! You can't start a selector with a combinator!
>> Ah, but we don't need to care what CSS thinks of our DOM-only API. We
>> can live and let live by building on ":scope" and specifying find* as
>> syntactic sugar, defined as:
>>  HTMLDocument.prototype.find =
>>  HTMLElement.prototype.find = function(rootedSelector) {
>>     return this.querySelector(":scope " + rootedSelector);
>>   }
>>   HTMLDocument.prototype.findAll =
>>   HTMLElement.prototype.findAll = function(rootedSelector) {
>>     return this.querySelectorAll(":scope " + rootedSelector);
>>   }
>> Of course, ":scope" in this case is just a special case of the ID
>> rooting hack, but if we're going to have it, we can kill both birds
>> with it.
>> Obvious follow up questions:
>> Q.) Why do we need this at all? Don't the toolkits already just do
>> this internally?
>> A.) Are you saying everyone, everywhere, all the time should need to
>> use a toolkit to get sane behavior from the DOM? If so, what are we
>> doing here, exactly?
>> Q.) Shorter names? Those are for weaklings!
>> A.) And humans. Who still constitute most of our developers. Won't
>> someone please think of the humans?
>> Q.) You're just duplicating things!
>> A.) If you ignore all of the things that are different, then that's
>> true. If not, well, then no. This is a change. And a good one for the
>> reasons listed above.
>> Thoughts?
Received on Wednesday, 19 October 2011 00:04:03 UTC

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