fix(diffs): Handle IME composition input

[necolas]

Fixes the following issue:

1. Open an editable diffs editor and place the caret in content.
2. Start a CJK IME or accented/dead-key composition.
3. Type a preview candidate, then commit it or press Esc to cancel.

Previously, each preview beforeinput was prevented and warned as an unknown input type, so the browser could not show native preview text and canceled composition text could still be inserted on compositionend.

Let insertCompositionText beforeinput events stay with the browser. Track composition updates and only commit non-canceled compositionend data into the editor model. Add regression coverage for preview, commit, warning noise, and canceled composition text.

[vercel]

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Project	Deployment	Actions	Updated (UTC)
pierre-docs-diffs	Ready	Preview	Jun 17, 2026 6:41am
pierre-docs-diffshub	Ready	Preview	Jun 17, 2026 6:41am
pierre-docs-trees	Ready	Preview	Jun 17, 2026 6:41am
pierrejs-diff-demo	Ready	Preview	Jun 17, 2026 6:41am

[chatgpt-codex-connector]

💡 Codex Review

pierre/packages/diffs/src/renderers/FileRenderer.ts

Line 334 in cdff209

this.textDoucmentCache.set(file, textDocument);

Use edited contents on full file rerenders

When an edit changes the line count, this remembers the live TextDocument but leaves renderCache.file/this.file pointing at the original contents. If a full file render is forced afterward (for example a theme/options change or cache eviction while the editor is mounted), the highlighter rebuilds code from stale file.contents while processFileResult uses the edited document's larger line count, so inserted lines index past code and the render throws Line doesnt exist. Update the cached file contents or use this TextDocument consistently during full rerenders.

---

pierre/packages/diffs/src/editor/editor.ts

Lines 678 to 680 in cdff209

	const composedRange = selectionRaw?.getComposedRanges({
	shadowRoots: [shadowRoot],
	})?.[0];

Guard unsupported composed selection APIs

On browsers or embedded WebViews that do not implement Selection.getComposedRanges (MDN marks it newly available: https://developer.mozilla.org/en-US/docs/Web/API/Selection/getComposedRanges), selecting inside the editor calls an undefined method from every selectionchange and throws before #selections can update, making the editable surface unusable. Check for the method and fall back to getRangeAt() or skip gracefully instead of invoking it unconditionally.

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[ije]

Nice!!!!

[necolas]

Fixed by the getComposedRanges issue by feature-checking the method and bailing out early. I did not use the getRangeAt() fallback. The editor renders inside a shadow root, and getRangeAt() doesn’t read across the shadow boundary like getComposedRanges does, so it would return the wrong range. Added a regression test that reproduces the throw without the guard.

Stale file contents on full rerenders seems to be pre-existing code in the highlight/render path, unrelated to this IME change. The suggested “update cached contents” fix risks regressing highlighting and can be tracked separately.

[ije]

Fixed by the getComposedRanges issue by feature-checking the method and bailing out early. I did not use the getRangeAt() fallback. The editor renders inside a shadow root, and getRangeAt() doesn’t read across the shadow boundary like getComposedRanges does, so it would return the wrong range. Added a regression test that reproduces the throw without the guard.

yep, it's vary trick to handle selection in shadow dom.

Stale file contents on full rerenders seems to be pre-existing code in the highlight/render path, unrelated to this IME change. The suggested “update cached contents” fix risks regressing highlighting and can be tracked separately.

i think this is ok. the editing won't trigger full-rerender with the stable file.