Implement ChildNode::before & ChildNode::after

[frewsxcv]

Continued from #6536

The current implementations of ChildNode::before and
ChildNode::after do not match the WHATWG spec. This commit updates the
implementations to match the spec.

Our current implementation of ChildNode::after passes all the WPT
tests. So I made sure to add a regression test that failed with the
current implementation. There are a few other unit tests I added
to exhaust other corner cases I encountered.

[Ms2ger]

-S-awaiting-review +S-needs-code-changes

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Reviewed 5 of 5 files at r1.
Review status: all files reviewed at latest revision, 6 unresolved discussions, all commit checks successful.

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^{components/script/dom/bindings/utils.rs, line 983 [r1] (raw file):}
I think I' prefer keeping this in node.rs.

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^{components/script/dom/bindings/utils.rs, line 987 [r1] (raw file):}
How about

nodes.find(|node| {
    not_in.iter().all(|n| {
        match n {
            &NodeOrString::eNode(ref n) => *n != node,
            _ => true,
        }
    })
})

?

(I like my iterator methods.)

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^{components/script/dom/node.rs, line 818 [r1] (raw file):}
.map(|s| s.root()) should be just .root()

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^{tests/wpt/web-platform-tests/dom/nodes/ChildNode-after.html, line 110 [r1] (raw file):}
Ditto

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^{tests/wpt/web-platform-tests/dom/nodes/ChildNode-before.html, line 110 [r1] (raw file):}
"all siblings" doesn't seem to be true.

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^{tests/wpt/web-platform-tests/dom/nodes/ChildNode-before.html, line 112 [r1] (raw file):}
You seem to have forgotten

var parent = document.createElement("div")
var x = parent.appendChild(document.createElement("a"));
var y = parent.appendChild(document.createElement("b"));
var z = parent.appendChild(document.createElement("c"));
var u = parent.appendChild(document.createElement("d"));
parent.appendChild(child);
child.before(z, u);

from #6536 (comment).

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Comments from the review on Reviewable.io

[frewsxcv]

^{tests/wpt/web-platform-tests/dom/nodes/ChildNode-before.html, line 112 [r1] (raw file):}
Out of curiosity, what is being tested in the codeblock you pasted that's not already being tested?

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Comments from the review on Reviewable.io

[frewsxcv]

^{components/script/dom/node.rs, line 818 [r1] (raw file):}
OptionalRootable (which presumably made this method on Option possible) was removed in #6150

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Comments from the review on Reviewable.io

[frewsxcv]

^{tests/wpt/web-platform-tests/dom/nodes/ChildNode-before.html, line 112 [r1] (raw file):}
I just added it in into the latest force push

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Comments from the review on Reviewable.io

[frewsxcv]

Addressed all the comments in the latest force push, with exception to the OptionalRootable.

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Comments from the review on Reviewable.io

[Ms2ger]

Reviewed 4 of 4 files at r2.
Review status: all files reviewed at latest revision, 4 unresolved discussions, all commit checks successful.

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^{components/script/dom/node.rs, line 818 [r1] (raw file):}
Bah. File an issue to bring it back.

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^{tests/wpt/web-platform-tests/dom/nodes/ChildNode-after.html, line 111 [r2] (raw file):}
Separate test

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^{tests/wpt/web-platform-tests/dom/nodes/ChildNode-before.html, line 111 [r2] (raw file):}
Separate test?

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^{tests/wpt/web-platform-tests/dom/nodes/ChildNode-before.html, line 126 [r1] (raw file):}
The viable sibling not being the first child, iirc

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Comments from the review on Reviewable.io

[frewsxcv]

^{components/script/dom/node.rs, line 818 [r1] (raw file):}
#6833

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Comments from the review on Reviewable.io

[frewsxcv]

^{tests/wpt/web-platform-tests/dom/nodes/ChildNode-before.html, line 112 [r1] (raw file):}
Ah, good point. That makes sense

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Comments from the review on Reviewable.io

[frewsxcv]

The latest force push addresses the second round of comments

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Comments from the review on Reviewable.io

[Ms2ger]

Thank you for your PR.

-S-awaiting-review +S-awaiting-merge

@bors-servo r+

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Reviewed 3 of 3 files at r3.
Review status: all files reviewed at latest revision, all discussions resolved, all commit checks successful.

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Comments from the review on Reviewable.io

[bors-servo]

📌 Commit 8cfccda has been approved by Ms2ger

[bors-servo]

⌛ Testing commit 8cfccda with merge 5873a5c...

[bors-servo]

☀️ Test successful - android, gonk, linux1, linux2, linux3, mac1, mac2, mac3