[BUGFIX] {{#in-element}} with DocumentFragment targets

[NullVoxPopuli]

Continuation of:

• [BUGFIX] {{#in-element}} with DocumentFragment targets, continued #21550

Which is a continuation of:

• [BUGFIX] DocumentFragment support — {{#in-element}} with DocumentFragment targets #21253

This is required to unblock using shadow-dom with out whack hacks.

See:

• [Quest]: Proper ShadowDOM support #20644

Demo of this PR working (REPL)

test code for the repl

import Component from '@glimmer/component';
import { trackedObject } from '@ember/reactive/collections';

const state = trackedObject({
  count: 0,
  inc: () => state.count++,
});


const fragment = document.createDocumentFragment();

setInterval(() => {
    console.log(fragment.textContent)
}, 250);

<template>
  check the console 

  <hr>
  as a separate PR we need to make fragments renderable
  today, folks would need a modifier to append the fragment to the DOM, 
  which could cause Glimmer to get confused by someone else managing DOM:
  {{fragment}}

  {{#in-element fragment}}
    text in a fragment
    {{log "in-element body"}}
    {{state.count}}

    <button onclick={{state.inc}}>inc</button>
  {{/in-element}}

  <hr> 
  
  outside the fragement is useful for testing reactivity
  <button onclick={{state.inc}}>inc</button>
</template> 

REPL deploy info

CI run: https://github.com/NullVoxPopuli/limber/actions/runs/31221384086
Preview PR: NullVoxPopuli/limber#2211
REPL with this change: https://test-ember-source-nvp-in-ele.limber-glimdown.pages.dev/

Perf is good.

---

Out of scope

• Making fragments renderable as values ({{this.fragment}}) — separate PR, per discussion.
• Destroying rendered content when the fragment's host is imperatively removed from the DOM. Glimmer doesn't observe external DOM mutation; teardown is driven by template lifecycle (toggling/destroying the {{#in-element}}), which is tested.
• insertBefore values other than null/undefined (unchanged from Element destinations).

[github-actions]

📊 Size report

Tarball size — 1.2 MB → 1.2 MB

dist/dev   0.06%↑

File	Before (Size / Brotli)	After (Size / Brotli)
./packages/shared-chunks/api-{hash}.js	26.2 kB / 5.8 kB	3%↑26.8 kB / 3%↑6 kB
./packages/shared-chunks/normalize-{hash}.js	2.2 kB / 617 B	15%↑2.6 kB / 23%↑761 B
./packages/shared-chunks/serialize-{hash}.js	3.6 kB / 1 kB	4%↑3.8 kB / 0.9%↑1.1 kB
Total (Includes all files)	2 MB / 489.8 kB	0.06%↑2.1 MB / 0.07%↑490.2 kB

---

dist/prod   0.06%↑

File	Before (Size / Brotli)	After (Size / Brotli)
./packages/shared-chunks/api-{hash}.js	25.7 kB / 5.7 kB	3%↑26.3 kB / 3%↑5.9 kB
./packages/shared-chunks/normalize-{hash}.js	2.2 kB / 617 B	15%↑2.6 kB / 23%↑761 B
./packages/shared-chunks/serialize-{hash}.js	3.6 kB / 1 kB	4%↑3.8 kB / 0.9%↑1 kB
Total (Includes all files)	1.9 MB / 447.2 kB	0.06%↑1.9 MB / 0.07%↑447.5 kB

---

smoke-tests/v2-app-template/dist   0.1%↑

File	Before (Size / Brotli)	After (Size / Brotli)
./assets/api-{hash}.js	288.5 kB / 77.8 kB	0.1%↑288.9 kB / -0.08%↓77.7 kB
Total (Includes all files)	340.6 kB / 94.8 kB	0.1%↑341 kB / -0.08%↓94.7 kB

---

smoke-tests/v2-app-hello-world-template/dist   0.03%↑

File	Before (Size / Brotli)	After (Size / Brotli)
Total (Includes all files)	132.4 kB / 37 kB	0.03%↑132.5 kB / 0.1%↑37.1 kB

_{🤖 This report was automatically generated by wyvox/pkg-size}

[NullVoxPopuli]

someone's editor doesn't strip unneeded invisible characters :P

[NullVoxPopuli]

meaningful change here

[NullVoxPopuli]

"a"