Hook for SVG and HTML script element insertion #575

annevk · 2018-02-19T14:30:01Z

Given http://software.hixie.ch/utilities/js/live-dom-viewer/?saved=4098 we need to do something special for script elements, in particular when inserted from a DocumentFragment node. It's my understanding this only affects script elements, but I haven't verified.

whatwg/html#1127 has an idea as to how to address this.

The text was updated successfully, but these errors were encountered:

annevk · 2018-02-19T14:37:36Z

Maybe the way to go here is to always notify post-DocumentFragment node insert for everyone. That seems to be what https://searchfox.org/mozilla-central/source/dom/base/nsINode.cpp#2404 is doing anyway.

annevk · 2018-02-19T15:11:05Z

Oh joy, if I change things to

<!DOCTYPE html>
<script>
 var s1 = document.createElement("script"); s1.textContent = "w(1 + ' ' + document.head.childElementCount); document.head.removeChild(s2)"
 var s2 = document.createElement("script"); s2.textContent = "w(2 + ' ' + document.head.childElementCount + ' ' + s2.parentNode)"
 var df = document.createDocumentFragment(); df.appendChild(s1); df.appendChild(s2)
 document.head.appendChild(df)
</script>

s2 will not execute in Chrome and Edge, but does execute in Firefox. Safari will throw an error for s1 because in Safari s2 is not in the tree yet when s1 executes.

So maybe another thing that's needed here is that script elements without parent do not execute?

annevk · 2018-02-20T10:16:09Z

Per https://html.spec.whatwg.org/#prepare-a-script browsers need to do a "connected" check, which means Firefox has a bug. (I want to check though if that check is correct or if it needs to be browsing-context connected.)

Another concern here is how this slightly post-insert notification interacts with slot changes. Basically, at what point do the shadow tree changes happen relative to notifying external consumers (which can execute script)?

annevk · 2018-02-20T11:41:27Z

With the following example I still get a slotchange event. I think that means that kind of tracking should happen before script execution, similar to queuing the mutation record.

<div id=host></div>
<script>
const host = document.getElementById("host"),
      shadow = host.attachShadow({ mode: "closed" }),
      slot = shadow.appendChild(document.createElement("slot")),
      df = document.createDocumentFragment(),
      s1 = df.appendChild(document.createElement("script")),
      s2 = df.appendChild(document.createElement("script"));

slot.addEventListener("slotchange", e => console.log(e));
s1.textContent = "df.appendChild(s1); df.appendChild(s2);";
s2.textContent = "console.log('hmm');";
host.appendChild(df);
</script>

annevk · 2018-02-20T14:01:07Z

I also tested custom elements:

<script>
customElements.define("ce-1", class CE1 extends HTMLElement {
  constructor() {
    super();
  }
  connectedCallback() {
    console.log("ce-1 connected");
  }
});

const df = document.createDocumentFragment(),
      s = df.appendChild(document.createElement("script")),
      ce1 = df.appendChild(document.createElement("ce-1"));
s.textContent = "df.appendChild(ce1);";
document.head.appendChild(df);
</script>

This logs "ce-1 connected" in Chrome and Firefox. It doesn't log anything in Safari. I'm inclined to side with Chrome and Firefox here.

Fixes whatwg/html#1127 and fixes #575.

autisticgeniushk · 2018-04-09T07:08:00Z

<div id=host></div>
<script>
const host = document.getElementById("host"),
      shadow = host.attachShadow({ mode: "closed" }),
      slot = shadow.appendChild(document.createElement("slot")),
      df = document.createDocumentFragment(),
      s1 = df.appendChild(document.createElement("script")),
      s2 = df.appendChild(document.createElement("script"));

slot.addEventListener("slotchange", e => console.log(e));
s1.textContent = "df.appendChild(s1); df.appendChild(s2);";
s2.textContent = "console.log('hmm');";
host.appendChild(df);
</script>

<script>
customElements.define("ce-1", class CE1 extends HTMLElement {
  constructor() {
    super();
  }
  connectedCallback() {
    console.log("ce-1 connected");
  }
});

const df = document.createDocumentFragment(),
      s = df.appendChild(document.createElement("script")),
      ce1 = df.appendChild(document.createElement("ce-1"));
s.textContent = "df.appendChild(ce1);";
document.head.appendChild(df);
</script>

nox · 2019-02-01T14:52:11Z

Another snippet that exposes differences between Firefox and Safari:

<body>
<select id="select"><option selected>1</option></select>
<script>
var select = document.getElementById("select");

var script = document.createElement("script");
script.textContent = "console.log(select.selectedIndex);";

var option = document.createElement("option");
option.textContent = "2";
option.selected = true;

select.append(script, option);
</script>

Changing selectedness of options is defined as part of inserting steps, AFAIK. This prints 0 in Safari and 1 in Firefox.

nox · 2019-02-04T11:32:37Z

Oh joy, if I change things to
<!DOCTYPE html>
<script>
 var s1 = document.createElement("script"); s1.textContent = "w(1 + ' ' + document.head.childElementCount); document.head.removeChild(s2)"
 var s2 = document.createElement("script"); s2.textContent = "w(2 + ' ' + document.head.childElementCount + ' ' + s2.parentNode)"
 var df = document.createDocumentFragment(); df.appendChild(s1); df.appendChild(s2)
 document.head.appendChild(df)
</script>
s2 will not execute in Chrome and Edge, but does execute in Firefox. Safari will throw an error for s1 because in Safari s2 is not in the tree yet when s1 executes.

So maybe another thing that's needed here is that script elements without parent do not execute?

Safari follows the current spec entirely for this one snippet, here is what the Live DOM Viewer says:

log: 1 1
error: NotFoundError: The object can not be found here. on line 1
log: 2 2 [object HTMLHeadElement]

Which means it first inserts s1 and runs it, which raises a NotFoundError because s2 is not a child of head, then it inserts s2 and runs it.

I'm not really sure what to do with this information, in which way do we want the spec to go? Do we want to specify less differences between inserting a DocumentFragment and a plain old node?

nox · 2019-02-04T11:37:25Z

This logs "ce-1 connected" in Chrome and Firefox. It doesn't log anything in Safari. I'm inclined to side with Chrome and Firefox here.

I guess that answers my question: we want children being inserted as part of a DocumentFragment node to behave more as if they were inserted as part of a plain old node.

For any given insert operation, these steps run for each inserted node synchronously after all node insertions are complete. This closes #732. The goal here is to separate the following: 1. Script-observable but not-script-executing insertion side effects - This includes synchronously applying styles to the document, etc... 2. Script-executing insertion side effects - This includes creating an iframe's document and synchronously firing its load event For any given call to insert, the above model allows us to keep all of (1) running synchronously after each node's insertion (as part of its insertion steps), while pushing all script-executing (or DOM tree-modifying or frame tree-modifying etc.) side effects to the new set of post-connection steps, which run synchronously during insertion, but _after all_ nodes finish their insertion. This essentially makes insertions "atomic" from the perspective of script, since script will not run until a given batch of DOM insertions are complete. This two-stage approach aligns the spec with a model most similar to Blink & Gecko's implementation, and fixes #808. This PR also helps out with whatwg/html#1127 and #575 (per #732 (comment)). To accomplish, this we audited all insertion side effects on the web platform in https://docs.google.com/document/d/1Fu_pgSBziVIBG4MLjorpfkLTpPD6-XI3dTVrx4CZoqY/edit#heading=h.q06t2gg4vpw, and catalogued whether they have script-observable side-effects, whether they invoke script, whether we have tests for them, and how each implementation handles them. This gave us a list of present "insertion steps" that should move to the "post-connection steps", because they invoke script and therefore prevent insertions from being "atomic". This PR is powerless without counterpart changes to HTML, which will actually _use_ the post-connection steps for all current insertion steps that invoke script or modify the frame tree. The follow-up HTML work is tracked here: - whatwg/html#10188 - whatwg/html#10241

For any given insert operation, these steps run for each inserted node synchronously after all node insertions are complete. This closes whatwg#732. The goal here is to separate the following: 1. Script-observable but not-script-executing insertion side effects - This includes synchronously applying styles to the document, etc... 2. Script-executing insertion side effects - This includes creating an iframe's document and synchronously firing its load event For any given call to insert, the above model allows us to keep all of (1) running synchronously after each node's insertion (as part of its insertion steps), while pushing all script-executing (or DOM tree-modifying or frame tree-modifying etc.) side effects to the new set of post-connection steps, which run synchronously during insertion, but _after all_ nodes finish their insertion. This essentially makes insertions "atomic" from the perspective of script, since script will not run until a given batch of DOM insertions are complete. This two-stage approach aligns the spec with a model most similar to Blink & Gecko's implementation, and fixes whatwg#808. This PR also helps out with whatwg/html#1127 and whatwg#575 (per whatwg#732 (comment)). To accomplish, this we audited all insertion side effects on the web platform in https://docs.google.com/document/d/1Fu_pgSBziVIBG4MLjorpfkLTpPD6-XI3dTVrx4CZoqY/edit#heading=h.q06t2gg4vpw, and catalogued whether they have script-observable side-effects, whether they invoke script, whether we have tests for them, and how each implementation handles them. This gave us a list of present "insertion steps" that should move to the "post-connection steps", because they invoke script and therefore prevent insertions from being "atomic". This PR is powerless without counterpart changes to HTML, which will actually _use_ the post-connection steps for all current insertion steps that invoke script or modify the frame tree. The follow-up HTML work is tracked here: - whatwg/html#10188 - whatwg/html#10241

domfarolino · 2024-09-03T19:30:36Z

@annevk I get the sense that we can close this issue now that #1261 and whatwg/html#10188 have landed. Do you agree?

annevk · 2024-09-04T08:14:44Z

Yeah, nice!

annevk added web reality needs tests Moving the issue forward requires someone to write tests labels Feb 19, 2018

annevk mentioned this issue Feb 19, 2018

Define timing of script execution in relation to DOM mutations better whatwg/html#1127

Closed

annevk mentioned this issue Feb 20, 2018

"prepare a script" and scripts moved to a different document whatwg/html#3486

Closed

annevk added a commit that referenced this issue Feb 20, 2018

Run insertion steps after DocumentFragment insertion completes

9d8c917

Fixes whatwg/html#1127 and fixes #575.

annevk mentioned this issue Feb 20, 2018

Run insertion steps after DocumentFragment insertion completes #576

Closed

This was referenced Feb 26, 2019

Use the new definition of the insertion steps whatwg/html#4354

Closed

Use a queue of deferred steps in the node insertion algorithm #732

Closed

annevk mentioned this issue Dec 9, 2019

Side effects due to tree insertion or removal (script, iframe) #808

Closed

yuzhe-han mentioned this issue Oct 29, 2020

Template batch mutations and side effects WICG/webcomponents#906

Open

domfarolino mentioned this issue Feb 28, 2024

Introduce DOM post-connection steps #1261

Merged

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annevk closed this as completed Sep 4, 2024

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Hook for SVG and HTML script element insertion #575

Hook for SVG and HTML script element insertion #575

annevk commented Feb 19, 2018

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annevk commented Feb 20, 2018

autisticgeniushk commented Apr 9, 2018 •

edited by nox

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domfarolino commented Sep 3, 2024

annevk commented Sep 4, 2024

Hook for SVG and HTML script element insertion #575

Hook for SVG and HTML script element insertion #575

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annevk commented Feb 19, 2018

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