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

From: Alex Russell <slightlyoff@google.com>
Date: Tue, 18 Oct 2011 17:47:26 +0100
Message-ID: <CANr5HFVPyHMOtQU2o75fMw-SfRHfQNv=pWWneJgZ19TkEkcVbA@mail.gmail.com>
To: Webapps WG <public-webapps@w3.org>
Cc: 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 5:42 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.

Sorry, this should say "meaning". APIs gain *meaning* through both use
and naming.

> 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 Tuesday, 18 October 2011 16:48:29 GMT

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