T17 round 2 fixes: merge keeps the newest caret in the lead by where it was given, and a composition cleared to nothing ends

TASKS.md

@@ -61,9 +61,9 @@ Per-component lines live in `tasks/`. Tags there:
 - [x] T16d Finance · Trading
 - [x] T16e Finance · Markets & assets
 - [ ] T17a Editor · Core
-- [ ] T17b Editor · Intelligence
-- [ ] T17c Editor · Search
-- [ ] T17d Editor · Panels
+- [x] T17b Editor · Intelligence
+- [x] T17c Editor · Search
+- [x] T17d Editor · Panels
 - [x] T17e Editor · Status items
 - [ ] T18 Terminal
 - [ ] T19 Git
@@ -230,11 +230,12 @@ Per-component lines live in `tasks/`. Tags there:
 | T16e | 1 | FAIL | a smaller loss than expected read as a miss |
 | T16e | 2 | PASS | |
 | T17a | 1 | FAIL | hidden numbers crashed the gutter; an edit with nothing to change tripped an assert; a read-only editor moved its caret and undid; a hint past a multi-line ghost fell off its row; the newest cursor lost the lead on merge; a slow composition left its pinyin in undo; gpui tests broke a featureless test build |
-| T17a | 2 | — | pending review |
+| T17a | 2 | FAIL | a selection touching the newest caret took the lead; a composition cleared to nothing stayed open and kept later edits out of undo |
+| T17a | 3 | — | pending review |
 | T17b | 1 | FAIL | two calls of one name shared a tree key; references counted lines, not matches |
-| T17b | 2 | — | pending review |
+| T17b | 2 | PASS | |
 | T17c | 1 | FAIL | a match on trailing spaces ran past its trimmed line; `**/` needed a folder |
-| T17c | 2 | — | pending review |
+| T17c | 2 | PASS | |
 | T17d | 1 | FAIL | a path match marked a project name mid-character; pin and remove also opened the row; number settings showed no places |
-| T17d | 2 | — | pending review |
+| T17d | 2 | PASS | |
 | T17e | 1 | PASS | |

src/editor/cursor.rs

@@ -38,14 +38,14 @@ impl Selection {
 }
 
 /// Sorted by where they start, overlapping selections joined into one; the last given, the primary, stays last.
-pub(crate) fn merged(mut all: Vec<Selection>) -> Vec<Selection> {
-    let primary = all
-        .last()
-        .expect("an editor keeps at least one cursor")
-        .range();
-    all.sort_by_key(|selection| selection.range().start);
+pub(crate) fn merged(all: Vec<Selection>) -> Vec<Selection> {
+    assert!(!all.is_empty(), "an editor keeps at least one cursor");
+    let primary = all.len() - 1;
+    let mut all: Vec<(usize, Selection)> = all.into_iter().enumerate().collect();
+    all.sort_by_key(|(_, selection)| selection.range().start);
     let mut out: Vec<Selection> = Vec::with_capacity(all.len());
-    for next in all {
+    let mut lead = 0;
+    for (given, next) in all {
         match out.last_mut() {
             Some(last)
                 if next.range().start < last.range().end
@@ -61,14 +61,10 @@ pub(crate) fn merged(mut all: Vec<Selection>) -> Vec<Selection> {
             }
             _ => out.push(next),
         }
+        if given == primary {
+            lead = out.len() - 1;
+        }
     }
-    let lead = out
-        .iter()
-        .position(|selection| {
-            let range = selection.range();
-            range.start <= primary.start && primary.end <= range.end
-        })
-        .expect("a merge keeps every cursor inside one");
     let lead = out.remove(lead);
     out.push(lead);
     out
@@ -174,6 +170,19 @@ pub(crate) fn replace_each(
 mod tests {
     use super::*;
 
+    #[test]
+    fn the_last_cursor_given_leads_even_beside_a_touching_selection() {
+        let all = merged(vec![
+            Selection {
+                anchor: 0,
+                head: 1,
+                goal: None,
+            },
+            Selection::caret(1),
+        ]);
+        assert_eq!(all.last(), Some(&Selection::caret(1)));
+    }
+
     #[test]
     fn overlapping_selections_join_and_carets_on_one_spot_become_one() {
         let joined = merged(vec![

src/editor/ime.rs

@@ -182,6 +182,9 @@ impl EntityInputHandler for CodeEditor {
         }
         self.apply(vec![(range.clone(), text.to_string())], true, cx);
         self.marked = (!text.is_empty()).then(|| range.start..range.start + text.len());
+        if self.marked.is_none() {
+            self.end_composition();
+        }
         let caret = match selected_utf16 {
             Some(inner) => range.start + from_utf16(text, inner.end),
             None => range.start + text.len(),

src/editor/tests.rs

@@ -194,6 +194,18 @@ fn a_slow_composition_undoes_in_one_step(cx: &mut TestAppContext) {
     });
 }
 
+#[gpui::test]
+fn a_composition_cleared_to_nothing_ends(cx: &mut TestAppContext) {
+    let (editor, cx) = editor("", cx);
+    editor.update_in(cx, |editor, window, cx| {
+        editor.replace_and_mark_text_in_range(None, "n", None, window, cx);
+        editor.replace_and_mark_text_in_range(None, "", None, window, cx);
+        editor.type_text("x", cx);
+        editor.undo(cx);
+        assert_eq!(editor.text(), "", "typing after the cleared mark undoes");
+    });
+}
+
 impl CodeEditor {
     /// Whether line `line` has a row now.
     fn frame_shows(&self, line: usize) -> bool {