dart:html should be split-up

[DartBot]

This issue was originally filed by @seaneagan

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The dart:html library is huge. This leads to some issues:

* makes the documentation extremely difficult to navigate

• importing dart:html really clutters your namespace
• prefixes must be used on top-level names in dart:html to avoid
  conflicts with other parts of the library
• if it is not split up now, it will only get bigger over time

It should be split up into smaller libraries. The challenge of course
is where to draw the boundaries for the smaller libraries. Here are
some approximate subsets which should probably be their own library:

SVG* (154 names!)

Audio* (21 names)

CSS* (18 names)

IDB* (18 names)

WebGL* (17 names)

Worker (13 names)

Speech* (12 names)

typed arrays (11 names)
 see https://developer.mozilla.org/en/JavaScript_typed_arrays

Canvas* (5 names)

geometry
  see issue #3107

[sethladd]

Removed Type-Defect label.
Added Type-Enhancement, Area-DOM, Triaged labels.

[rakudrama]

Issue #3949 has been merged into this issue.

[rakudrama]

Concerns from Issue #3949 which has been merged into this issue:

"""
Reported by fedor.korotkov, Yesterday (26 hours ago)
Currently there is a one huge file html_dartium.dart(1192 classes) that contains generated html stubs.

It would be great if you group some classes and extract them to separate files.

Comment 1 by rbeeger, Yesterday (25 hours ago)
Fedor's main motivation for this report is most likely that it takes some time for the IDEA Dart plugin to parse this file when it is opened.

But there is one more reason for splitting up this file. Separating it into several files based on the topic would help exploration of this part of dart's SDK.

So if I were interested in WebGL I would look into webgl.dart. For SVG I would look into svg.dart.
"""

I don't think we will be able to achieve much tool speedup by partitioning the library.
One motivation of partitioning dart:html is to exclude SVG* from the namespace.

Consider this is valid code fragment:
   var element = document.body;
   element.innerHTML = createAString();
   var innerElement = element.query('#Bob');
   print(innerElement.height);

createAString() could contain almost anything, including an SVGRectElement, e.g.
'<svg><rect id="Bob">...</rect>...</svg>'

The compiler needs to know that .height could be returning an SVGAnimatedLength (SVGRectElement.height) as well as a number (ImageElement.height) or String (TableCellElement.height).

In order for this to happen, all the SVG* names need to be available to the compiler, otherwise the compiler could make the incorrect inference that only strings and numbers could be returned and generate 'optimized' code that does not work.
In order for the compiler to generate correct code, a partitioned library would be implemented as a set of libraries that each re-export a subset of the current monolithic library. This does not get rid of the need to parse the whole monolithic library.

Since we don't want the editor to be inconsistent with the library, it consumes the same version of the library as the compiler, so would still need to parse all 500+ interfaces.

The in-editor experience would still be better since the editor can choose suggestions on the basis of names reachable from the imports rather than available on all instances reaching that point in the code.

[DartBot]

This comment was originally written by fedor.korotko...@gmail.com

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In my case it take a few seconds to find all implementations for each class in that file. I will fix it but the main reason for me as a developer is impossibility to work with such file even in text editor. For example I can't look at both WebGL and geometry at the same time. Or simple navigation becomes uncomfortable.

[vsmenon]

cc @rakudrama.
Added this to the M1 milestone.

[iposva-google]

Removed Area-DOM label.
Added Area-HTML label.

[vsmenon]

Removed this from the M1 milestone.
Added this to the Later milestone.
Removed Priority-Medium label.
Added Priority-High label.

[blois]

Removed this from the Later milestone.
Added this to the M2 milestone.

[blois]

Set owner to @blois.
Added Accepted label.

[blois]

SVG, Audio and Indexed DB have all been broken out. I'm hesitant to break CSS apart from HTML as the scenarios seem inseparable.

I'd like to treat breaking out anything else as separate issues. Note that breaking out WebGL is under consideration, but right now none of the others are.

Note that another one which we should consider is RTC as well.

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Added Fixed label.