Redmine

Since #43095 (6.1.0), pressing Enter after a list item runs the list-autofill Stimulus controller. Its insert branch cancels the native line break and splices the marker with:

this.input.value = newValue
this.input.setSelectionRange(newCursor, newCursor)

Assigning input.value programmatically resets the browser's undo stack, and setSelectionRange does not scroll the textarea in Chrome. Two user-visible defects on every Enter inside a list:

1. Undo is destroyed. Everything typed before the Enter becomes unrecoverable with Ctrl+Z. Measured in Chromium on a stock 6.1.3 new-issue form: type * item one, Enter (marker auto-inserted), type item two, then Ctrl+Z 8x -> textarea stops at
"* item one\n* ". With the controller detached, the same keystrokes undo to empty.
2. Caret left off-screen. When the textarea is scrolled (long note, caret at bottom), the native Enter scroll never happens (the event was canceled). The new list line is not visible until the next character is typed.

The remove branch (Enter on an empty item) uses setRangeText, which is also not undoable in Chromium.

Proposed fix (patch attached):

• insert: do not cancel the event. Let the native line break run — it creates a normal undo entry and scrolls the caret into view — and append the marker at the caret from a one-shot input (insertLineBreak) listener via document.execCommand('insertText'), falling back to setRangeText where execCommand is unavailable.
• remove: select the marker range and use document.execCommand('delete') (same fallback), so the removal is undoable.

Verified in Chromium (headless, Playwright) against 6.1.3 with the patch applied:

• markers still auto-insert/remove for Textile and CommonMark lines
• 8x Ctrl+Z fully reverts a typed list (identical to a controller-less textarea); one Ctrl+Z reverts break+marker in a single step
• scrollTop after Enter matches native exactly (540 -> 555 in the test layout); Ctrl+Z after marker-removal restores the marker
• execCommand is deprecated but universally supported for insertText/delete in textareas, and core already relies on it (copy-to-clipboard).

1. Probe data (2026-08-10, sameersbn/redmine:6.1.3-2, bundled Chromium)

Scroll (textarea 184px client, 40 list lines, caret at bottom; "visible px" = height of caret line inside the viewport right after Enter):