editor: Fix Shift-click selection after cursor movement

[saberoueslati]

Context

Shift-click sometimes extended a selection from an earlier word boundary after double-clicking a word and moving the cursor with the arrow keys. Cursor movement changed the selection but left the word or line selection mode active, so the next Shift-click reused stale selection bounds. Selection movement now resets the mode to character mode whenever it changes the selection, while preserving valid empty line selections that have not been moved.

Closes #59913.

Behavior before the fix :

Screencast.from.2026-07-15.13-21-51.webm

Behavior after the fix :

Screencast.from.2026-07-15.13-19-38.webm

How to Review

crates/editor/src/selections_collection.rs: MutableSelectionsCollection::move_with now resets the selection mode to character mode when movement changes a selection.

crates/editor/src/editor_tests.rs: Regression tests cover Shift-click after collapsing a word selection and confirm that a valid empty line selection retains line-wise extension behavior.

Self-Review Checklist

• I've reviewed my own diff for quality, security, and reliability
• Unsafe blocks (if any) have justifying comments
• The content is consistent with the UI/UX checklist
• Tests cover the new/changed behavior
• Performance impact has been considered and is acceptable

Release Notes:

• Fixed Shift-click sometimes extending selections from a previous word or line boundary.

[SomeoneToIgnore]

Thank you for the nice find.

The fix though, is rather confusing as move_offsets_with just below the change did not get change too, despite being identical?

The other large question is that before, the select mode was changed only at the end of each selection in the editor:

zed/crates/editor/src/selection.rs

Lines 1445 to 1453 in 93b846b

	self.change_selections(SelectionEffects::no_scroll(), window, cx, |s| {
	s.select(selections);
	s.clear_pending();
	if s.is_extending() {
	s.set_is_extending(false);
	} else {
	s.set_select_mode(pending_mode);
	}
	});

This all signals that we need to fix things elsewhere, not paper things over.

[saberoueslati]

@SomeoneToIgnore I’ve reworked the fix so MutableSelectionsCollection::select resets the selection mode to Character. Both move_with and move_offsets_with already funnel changed selections through select, so they now behave consistently without duplicating the reset in individual movement methods.

Since end_selection also calls select, it now captures the appropriate mode beforehand and restores it afterward. This preserves word/line granularity for active selection gestures while preventing stale modes from surviving later selection replacements.

I also added a regression test covering the move_offsets_with path. The focused tests pass, as does the full editor library suite: 850 passed and 1 ignored.

[SomeoneToIgnore]

That makes much more sense, thank you a lot for the investigation!