Add custom elements to HTML #1012

domenic · 2016-04-07T23:23:52Z

This upstreams custom elements into the HTML Standard, instead of having
them be in a separate spec that monkeypatches HTML extensively. This
builds on previous work in whatwg/dom#204.

See https://rawgit.com/w3c/webcomponents/15a203c8393aef0df7223ab1d43406aa11a7e71e/spec/custom/index.html
for the source material, in particular the sections labeled "HTML+". All
changes while upstreaming were editorial in nature.

Review appreciated, especially in the form of pushing fixups to the branch.

annevk · 2016-04-08T03:04:41Z

images/content-venn.svg

@@ -108,6 +108,7 @@
     <li><code>var</code></li>
     <li><code>video</code></li>
     <li><code>wbr</code></li>
+     <li><span>custom tags</span></li>


The plan is to rename this in a follow up commit?

Yeah, I guess, if we ever figure something out.

Well I think we need to. "tags" is just super wrong.

annevk · 2016-04-08T03:08:51Z

I should have asked this earlier, where exactly does NewTarget come from? Is that worthy of a note or a cross-reference?

domenic · 2016-04-08T04:49:57Z

I should have asked this earlier, where exactly does NewTarget come from? Is that worthy of a note or a cross-reference?

I think it would be ideal to cross-reference, but ES does not have a definition for it; instead as far as I can tell it's just an ambient floating thing all ES algorithms get. I'll file an ES bug.

domenic · 2016-04-08T04:54:59Z

source

+   <li><p>If <var>name</var> is <code>blink</code>, <code>bgsound</code>, <code>isindex</code>,
+   <code>multicol</code>, <code>nextid</code>, or <code>spacer</code>, return
+   <code>HTMLUnknownElement</code>.</p></li>
+   <!-- These have to be explicitly listed because technically we define these elements in HTML,


This helps with https://www.w3.org/Bugs/Public/show_bug.cgi?id=27877, but probably doesn't completely take care of it, as basefont might still be confusing.

domenic · 2016-04-08T18:08:38Z

I pushed fixes addressing the issues I noted on @annevk's commit. One interesting issue it raised is defining element interface for obsolete elements better. I will open a new issue on that.

domenic · 2016-04-08T20:14:39Z

Should "Core concepts" be named "Processing model"? Maybe not, since so much of the processing model is defined elsewhere...

annevk · 2016-04-09T10:16:57Z

source

@@ -9574,26 +9574,28 @@ interface <dfn>HTMLUnknownElement</dfn> : <span>HTMLElement</span> { };</pre>
  <span>HTML namespace</span> is determined as follows:</p>

  <ol>
-   <li><p>If <var>name</var> is <code>blink</code>, <code>bgsound</code>, <code>isindex</code>,
+   <li><p>If <var>name</var> is <code>bgsound</code>, <code>blink</code>, <code>isindex</code>,
   <code>multicol</code>, <code>nextid</code>, or <code>spacer</code>, return
   <code>HTMLUnknownElement</code>.</p></li>
   <!-- These have to be explicitly listed because technically we define these elements in HTML,
        albeit as obsolete. -->


This comment is obsolete with this commit, no?

Yeah good catch

annevk · 2016-04-09T10:21:25Z

Would you mind if I added ", then" to conditionals?

annevk · 2016-04-09T10:21:58Z

Although with all the don't squash that might get a little labor intensive...

domenic · 2016-04-09T15:35:59Z

You can add it, it's fine. Maybe don't add it to the sections touched in "don't squash" and I can do those myself when I rebase and rearrange commits.

annevk · 2016-04-13T04:43:55Z

I think it's all good now. I have fixed up the commits to add "then" and removed "don't squash" from the titles. Admittedly I have relied in part on my earlier review of the algorithms. Since I assume you just moved them around.

zcorpan · 2016-04-13T11:15:53Z

source

+   data-x="concept-custom-element-definition-name">name</span> <var>name</var>, then return that
+   entry's <span data-x="concept-custom-element-definition-constructor">constructor</span>.</p></li>
+
+   <li><p>Otherwise, return undefined.</p></li>


I think it's more common to return null from a method. Why undefined?

I noticed that. I suspect @domenic wants to mimic Map semantics.

Yes, exactly, map-like get() methods need to return undefined.

zcorpan · 2016-04-13T11:41:49Z

There needs to be a normative statement saying that <html is> is invalid, e.g. "The is attribute must not be specified."

zcorpan · 2016-04-13T12:13:29Z

Do we want to allow any attribute on customized built-in elements? In particular those in the obsolete section? Note that embed allows any attribute except those that are obsolete (e.g. name).

zcorpan · 2016-04-13T12:29:22Z

+   <dt><var>window</var> . <code data-x="dom-window-customElements">customElements</code> . <code
+   data-x="dom-CustomElementsRegistry-define">define</code>(<var>name</var>,
+   <var>constructor</var>)</dt>

These typically have a subdfn attribute (which I think is for developers.whatwg.org?).

zcorpan · 2016-04-13T12:53:49Z

(Reached the end of the diff; no more comments.)

domenic · 2016-04-13T13:30:21Z

There needs to be a normative statement saying that <html is> is invalid, e.g. "The is attribute must not be specified."

Why?

Autonomous custom elements should also not allow the is attribute, right?

Good catch, thanks.

Shouldn't this use removeAttribute?

Either would work, I imagine. -1 is more explicit IMO?

Do we want to allow any attribute on customized built-in elements? In particular those in the obsolete section? Note that embed allows any attribute except those that are obsolete (e.g. name).

Hmm. We probably should? I have no real idea how to phrase this though, or which sections to edit. Suggestions?

These typically have a subdfn attribute (which I think is for developers.whatwg.org?).

Thanks, will add.

zcorpan · 2016-04-13T14:06:11Z

Either would work, I imagine. -1 is more explicit IMO?

-1 means it's still focusable if you click it. Also the code above uses removeAttribute and the prose talks about removing the attribute.

zcorpan · 2016-04-13T14:08:00Z

Why?

The content model is normative, but nothing says the attributes list is. The rest of the spec addresses each attribute individually in prose I believe. So right now it's a statement of fact that's not backed up by anything normative. :-)

annevk · 2016-04-13T14:21:19Z

Why can't is be specified on html anyway? It works, right?

domenic · 2016-04-13T14:27:14Z

Yeah, that was my question.

I agree with you now about removeAttribute; thanks for that.

zcorpan · 2016-04-13T15:04:23Z

Oh, I don't mind allowing is on html. Then remove , except the <code data-x="attr-is">is</code> attribute.

zcorpan · 2016-04-13T15:04:43Z

Hmm. We probably should? I have no real idea how to phrase this though, or which sections to edit. Suggestions?

How about...

diff --git a/source b/source
index 0967e3a..a627fa4 100644
--- a/source
+++ b/source
@@ -28002,8 +28002,8 @@ attribute, set the <span>browsing context name</span> of the element's <span>nes
   <p class="note">All attributes in <span>HTML documents</span> get lowercased automatically, so the
   restriction on uppercase letters doesn't affect such documents.</p>

-  <p class="note">The four exceptions are to exclude legacy attributes that have side-effects beyond
-  just sending parameters to the <span>plugin</span>.</p>
+  <p class="note">The four exceptions are to exclude <span>obsolete attributes</span> that have
+  side-effects beyond just sending parameters to the <span>plugin</span>.</p>

   <div w-nodev>

@@ -67011,9 +67011,13 @@ console.log(plasticButton2.getAttribute("is")); // will output "plastic-button"<

   <p>An <span>autonomous custom element</span> does not have any special meaning: it
   <span>represents</span> its children. A <span>customized built-in element</span> inherits the
-  semantics of the element that it extends. Both types of <span>custom element</span> may have any
-  non-namespaced attributes that are relevant to the element's functioning, as determined by the
-  element's author.</p>
+  semantics of the element that it extends.</p>
+
+  <p>Any namespace-less attribute, that are relevant to the element's functioning, as determined by
+  the element's author, may be specified on both types of <span data-x="custom element">custom
+  elements</span>, except those that are defined as being <span data-x="obsolete
+  attributes">obsolete</span> for that element, so long as its name is <span>XML-compatible</span>
+  and contains no <span>uppercase ASCII letters</span>.</p>

   <p>A <dfn data-export="">valid custom element name</dfn> is a sequence of characters
   <var>name</var> that meets all of the following requirements:</p>
@@ -111655,7 +111659,8 @@ if (s = prompt('What is your name?')) {

   <h3>Non-conforming features</h3>

-  <p>Elements in the following list are entirely obsolete, and must not be used by authors:</p>
+  <p>Elements in the following list are entirely <dfn data-x="obsolete elements">obsolete</dfn>, and
+  must not be used by authors:</p>

   <dl><!-- alphabetical by first element in the group, except CSS goes last -->

@@ -111736,8 +111741,8 @@ if (s = prompt('What is your name?')) {

   <hr>

-  <p>The following attributes are obsolete (though the elements are still part of the language), and
-  must not be used by authors:</p>
+  <p>The following attributes are <dfn data-x="obsolete attributes">obsolete</dfn> (though the
+  elements are still part of the language), and must not be used by authors:</p>

   <dl><!-- alphabetical by element then attribute of first item in group, except CSS goes last -->

Note: I copied the requirements from embed that the attribute name be lowercase and XML-compatible.

Additional thoughts:

The requirements on element names are similar but are defined differently. Editorial but is a bit inconsistent right now.
Why are any attributes allowed on customized built-in elements? Are they not as problematic for future extensions to the language as any attribute on standard elements?

domenic · 2016-04-13T15:38:24Z

Then remove , except the <code data-x="attr-is">is</code> attribute.

Huh, I didn't notice that. I think it must have been intended to go on autonomous built-in elements; I have no idea how it made it to <html>.

Why are any attributes allowed on customized built-in elements? Are they not as problematic for future extensions to the language as any attribute on standard elements?

That's a good point. Let's leave them invalid for now, and address this in a follow-up issue.

domenic · 2016-04-13T15:56:00Z

@zcorpan please take a look, made a fixup commit for easier reviewing.

zcorpan · 2016-04-13T21:10:02Z

LGTM

This upstreams custom elements into the HTML Standard, instead of having them be in a separate spec that monkeypatches HTML extensively. This builds on previous work in whatwg/dom#204. See https://rawgit.com/w3c/webcomponents/15a203c8393aef0df7223ab1d43406aa11a7e71e/spec/custom/index.html for the source material, in particular the sections labeled "HTML+". Most changes while upstreaming were editorial in nature, with the following exceptions: - Changes were made to the "element interface" section to nail down underspecified edge cases, and fix https://www.w3.org/Bugs/Public/show_bug.cgi?id=27877. - Changes were made to the authoring conformance criteria for attributes on custom elements. A notable change included in this upstreaming is that the order of attributes created by the parser is now well-defined. See WICG/webcomponents#474 for discussion, as well as https://www.w3.org/Bugs/Public/show_bug.cgi?id=17871.

"custom tag" becomes "autonomous custom element", and "type extension" becomes "customized built-in element". Fixes WICG/webcomponents#434.

Fixes WICG/webcomponents#445.

annevk · 2016-04-14T06:16:44Z

\o/

(Do we want to keep this branch alive as we did in DOM?)

domenic · 2016-04-14T13:00:40Z

Yeah, we probably should, and I can also help maintain a similar wiki page.

annevk · 2016-04-14T13:03:48Z

Protected.

Fixes #1015, and matches all non-Gecko engines. Before #1012 the spec was unclear on this; in #1012 the spec sided with Gecko, but per #1015 it is better to side with the majority.

Fixes #1015, and matches all non-Gecko engines. Before #1012 the standard was unclear on this; in #1012 the standard sided with Gecko, but per #1015 it is better to side with the majority.

domenic assigned annevk Apr 7, 2016

domenic added the addition/proposal New features or enhancements label Apr 7, 2016

annevk reviewed Apr 8, 2016
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domenic reviewed Apr 8, 2016
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domenic mentioned this pull request Apr 8, 2016

Where is the spec? WICG/webcomponents#481

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domenic force-pushed the customelements branch from 679d17e to d645d1d Compare April 8, 2016 18:07

domenic mentioned this pull request Apr 8, 2016

Element interfaces across browsers #1015

Closed

domenic mentioned this pull request Apr 8, 2016

Rename custom tag WICG/webcomponents#434

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domenic force-pushed the customelements branch from ef3a7c2 to 07b0b3c Compare April 8, 2016 21:25

domenic mentioned this pull request Apr 8, 2016

Permit retrieval of registered classes from window.customElements WICG/webcomponents#445

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annevk reviewed Apr 9, 2016
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This was referenced Apr 10, 2016

Define "user agent" #1021

Closed

Specify order of attributes for parser-created elements #1035

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annevk force-pushed the customelements branch from 8898ec9 to 1804c62 Compare April 13, 2016 04:42

annevk assigned domenic and unassigned annevk Apr 13, 2016

zcorpan reviewed Apr 13, 2016
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domenic force-pushed the customelements branch from 1804c62 to 3161de2 Compare April 13, 2016 15:55

domenic assigned zcorpan and unassigned domenic Apr 13, 2016

domenic added 3 commits April 13, 2016 17:27

Rename the types of custom elements

7858636

"custom tag" becomes "autonomous custom element", and "type extension" becomes "customized built-in element". Fixes WICG/webcomponents#434.

Add customElements.get() to retrieve a custom element constructor

1d596a5

Fixes WICG/webcomponents#445.

domenic force-pushed the customelements branch from 3161de2 to 1d596a5 Compare April 13, 2016 21:39

domenic merged commit 1d596a5 into master Apr 13, 2016

domenic mentioned this pull request Apr 20, 2016

Use HTMLPreElement for xmp and listing #1083

Merged

domenic added the topic: custom elements Relates to custom elements (as defined in DOM and HTML) label May 17, 2016

annevk deleted the customelements branch August 18, 2016 10:22

TimvdLippe mentioned this pull request Sep 16, 2018

Clarify status of Web Components standard vuejs/v2.vuejs.org#1795

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Add custom elements to HTML #1012

Add custom elements to HTML #1012

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Add custom elements to HTML #1012

Add custom elements to HTML #1012

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