Bug 126605 – DOM serialization: < and > should not be quoted in HTML attribute values

• Component: DOM
• Status: RESOLVED CONFIGURATION CHANGED

[Victor Costan]

== What steps will reproduce the problem?

1. Open the document and look at the attribute serialization in the HTML output and XML output.

== What is the expected result?

The HTML serialization should contain "< >" instead of "&lt; &gt;".

== What happens instead?

< and > in the attribute value are incorrectly escaped during serialization.

In the HTML case, the DOM parsing and serialization specification defers to the HTML specification: http://www.w3.org/html/wg/drafts/html/master/syntax.html#attribute's-serialized-name

Steps 1-3 under the "Escaping a string" heading are relevant to attributes.

== Please provide any additional information below.

Firefox, IE and Chromium do not quote < and >. The fix happened pretty recently in Chromium, so it only shows up in Canary builds.

I will prepare a patch for this bug soon.

[Victor Costan]

Created attachment 220575 [details]
Patch

[Victor Costan]

Adam, this is a port of the following Blink CL that you reviewed.
https://codereview.chromium.org/117103003/

Alexey, can you please take a look?

[Alexey Proskuryakov]

Comment on attachment 220575 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=220575&action=review

> Source/WebCore/ChangeLog:10
> +        * editing/MarkupAccumulator.h: EntityMaskInHTMLAttributeValue matches DOM spec.

Is this actually the only place where XMLSerializer does not match the "specification" for HTML documents? I thought it didn't care whether it's HTML or XML, unlike in Firefox.

> LayoutTests/fast/dom/dom-parse-serialize.html:43
> +    '<?xml version="1.0"?>\n<!DOCTYPE doc [\n<!ATTLIST d id ID #IMPLIED>\n]>\n<doc>\n  <foo xmlns="foobar">One</foo> <x:bar xmlns:x="barfoo">Two</x:bar>\n  <d id="id3">Three</d>\n<f id="&amp;&lt;&gt;>">Four&amp;&lt;&gt;</f><empty/><empty></empty></doc>\n';

It's confusing that this change for how HTML is serialized includes a change to an XML test.

[Victor Costan]

(In reply to comment #3)
> (From update of attachment 220575 [details])
> View in context: https://bugs.webkit.org/attachment.cgi?id=220575&action=review
> 
> > Source/WebCore/ChangeLog:10
> > +        * editing/MarkupAccumulator.h: EntityMaskInHTMLAttributeValue matches DOM spec.
> 
> Is this actually the only place where XMLSerializer does not match the "specification" for HTML documents? I thought it didn't care whether it's HTML or XML, unlike in Firefox.

To the best of my understanding, MarkupAccumulator is used indirectly by Element.innerHTML and Element.outerHTML too.

HTMLElement::{innerHTML, outerHTML} (WebCore/html/HTMLElement.cpp) ->
    WebCore::createMarkup (WebCore/editing/markup.cpp) ->
    WebCore::createMarkupInternal (WebCore/editing/markup.cpp) ->
    StyledMarkupAccumulator::serializeNodes (WebCore/editing/markup.cpp) ->
    StyledMarkupAccumulator::traverseNodesForSerialization (WebCore/editing/markup.cpp) ->
    MarkupAccumulator::appendStartTag (WebCore/editing/MarkupAccumulator.cpp) -> 
    MarkupAccumulator::appendStartMarkup (WebCore/editing/MarkupAccumulator.cpp) -> 
    StyledMarkupAccumulator::appendElement (WebCore/editing/markup.cpp) -> 
    MarkupAccumulator::appendElement (WebCore/editing/MarkupAccumulator.cpp) -> 
    MarkupAccumulator::appendAttribute (WebCore/editing/MarkupAccumulator.cpp) -> 
    MarkupAccumulator::appendAttributeValue (WebCore/editing/MarkupAccumulator.cpp)

MarkupAccumulator::appendAttributeValue is where the mask is chosen, depending on the document type. So changing the mask does impact the serialization of HTML documents.

Also, the new layout test that I added shows that either I'm right, or there's another code path that I don't see which uses the same mask. "git grep" tells me the mask name isn't referenced anywhere in WebCore, so I'm reasonably certain that I got this right.

> 
> > LayoutTests/fast/dom/dom-parse-serialize.html:43
> > +    '<?xml version="1.0"?>\n<!DOCTYPE doc [\n<!ATTLIST d id ID #IMPLIED>\n]>\n<doc>\n  <foo xmlns="foobar">One</foo> <x:bar xmlns:x="barfoo">Two</x:bar>\n  <d id="id3">Three</d>\n<f id="&amp;&lt;&gt;>">Four&amp;&lt;&gt;</f><empty/><empty></empty></doc>\n';
> 
> It's confusing that this change for how HTML is serialized includes a change to an XML test.

I added that because I wanted to make sure that > can be read from an XML attribute in both its un-escaped and escaped form (&gt;) and it always comes out as &gt; I didn't see this covered in other tests. I thought it's a useful check, from a black-box testing perspective. I can remove it if you disagree.

[Victor Costan]

Created attachment 230040 [details]
Patch

[Victor Costan]

Chris, can you please take a look at this?

It should be similar to a Blink change that you've seen recently.
https://codereview.chromium.org/117103003

Also, at this point, all other major browsers converge on this behavior.

[Victor Costan]

The patch still applies cleanly. I would be grateful for a review.

[Ryosuke Niwa]

Comment on attachment 230040 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=230040&action=review

> Source/WebCore/editing/MarkupAccumulator.h:55
> +    EntityMaskInAttributeValue = EntityAmp | EntityQuot | EntityLt | EntityGt,

Since we didn't change flags in EntityMaskInAttributeValue, we should revert the change to this line.

[Victor Costan]

Created attachment 236742 [details]
Patch

[Victor Costan]

Thank you for the feedback!

I uploaded a new patch.

Can you please take a look and CQ+ if the patch is acceptable?

[Victor Costan]

Ryoskue: ping?

Can you please take another look at this?
The efl-wk2 EWS error doesn't appear to be related to the patch.

Thank you!

[Ahmad Saleem]

From attached URL JSBin - I get following:

*** Safari 15.6 on macOS 12.5 ***

Serialized HTML: <div quoteme="< > &amp; &quot; ' &nbsp;"></div>

Serialized XML: <div xmlns="http://www.w3.org/1999/xhtml" quoteme="&lt; &gt; &amp; &quot; '  "></div>

*** Firefox Nightly 105 ***

Serialized HTML: <div quoteme="< > &amp; &quot; ' &nbsp;"></div>

Serialized XML: <div xmlns="http://www.w3.org/1999/xhtml" quoteme="&lt; &gt; &amp; &quot; '  "></div>

*** Chrome Canary 106 ***

Serialized HTML: <div quoteme="< > &amp; &quot; ' &nbsp;"></div>

Serialized XML: <div xmlns="http://www.w3.org/1999/xhtml" quoteme="&lt; &gt; &amp; &quot; '  "></div>

_____________

Do we need to use anything else? Just wanted to share updated test cases. Thanks!

[Ryosuke Niwa]

This is working as intended now.