Place the caret before an inline decorator when Gecko drops the selection

[lyubomir-bozhinov]

Fixes #1149.

The bug

With a mention at the start of a paragraph, clicking just before it and typing did nothing in Firefox. The keystrokes were silently dropped.

Why

The click leaves the editor with no selection at all, so there is nothing for typing to act on. document.caretPositionFromPoint() at the same coordinates explains why:

	resolves to	resulting selection
Blink	P @0 — the paragraph itself	RangeSelection, element point, offset 0
Gecko	#text:"Zacharias" @0 — inside the mention	null (rangeCount: 0)

Gecko descends into the decorator's contenteditable="false" subtree. That text node is rendered by the decorator and is not part of the editor state, so no selection point maps to it and Lexical ends up with none. There is no text node before the mention to hold a caret, so nothing recovers it.

The fix

CLICK_COMMAND already handles clicks that land on a decorator. This adds the neighbouring case: when a click leaves us with no selection and the clicked point resolves inside an inline decorator, place the caret at that decorator's index in its parent — the same element point Blink produces natively.

The guard is $getSelection() !== null, so Blink and WebKit never reach this path.

Scope

Deliberately limited to inline decorators (mentions), which is the reported bug. Block attachments (e.g. an uploaded file) have an analogous Gecko caret-drop at their vertical boundary, but the correct before/after placement there depends on the click's Y position rather than X, so it is a separate change rather than something to fold in here. The isInline() guard makes the boundary explicit, and the method is named #placeCaretBeforeInlineDecorator because the null-selection case only ever occurs on the leading edge (clicking after an inline decorator resolves natively in Gecko).

Tests

test/browser/tests/prompts/typing_before_mention.test.js, driven with a real page.mouse.click():

• clicking before a leading mention places the caret before it — fails on Firefox without this change, passes with it
• clicking after a trailing mention places the caret after it — guards against the new path hijacking clicks Gecko already handles

Both assert the mention still exists (toHaveCount(1)) so the ordering check can't pass vacuously. Verified on Chromium, Firefox and WebKit. prompts/ and attachments/ are green on Firefox; yarn lint and yarn test are clean.

[claude]

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[Copilot]

Pull request overview

Fixes a Firefox/Gecko-specific edge case where clicking immediately before a leading inline decorator (mention) leaves Lexical with no selection, causing subsequent typing to be dropped. The change detects the null-selection + inline-decorator-from-point condition and explicitly places the caret at the decorator’s index in its parent, matching the element-point behavior seen in Blink.

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Changes:

• Extend CLICK_COMMAND handling to recover from Gecko’s “null selection” by placing the caret before an inline decorator found at the click point.
• Add a Playwright regression test covering typing before a leading mention on Firefox, plus a guard test for clicking after a trailing mention.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/editor/selection.js	Adds a null-selection recovery path for Gecko clicks that resolve inside inline decorator DOM, placing the caret before the decorator.
test/browser/tests/prompts/typing_before_mention.test.js	Adds browser-level coverage to reproduce and prevent regressions for typing adjacent to mentions (especially Firefox).

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Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.