Fix editor::SplitSelectionIntoLines adding an extra line at the end (#25053)

Closes #4795

Release Notes:

- Fixed `editor::SplitSelectionIntoLines` adding an extra line at end
of selection

crates/editor/src/editor.rs

@@ -9122,21 +9122,32 @@ impl Editor {
         window: &mut Window,
         cx: &mut Context<Self>,
     ) {
-        let mut to_unfold = Vec::new();
+        let selections = self
+            .selections
+            .all::<Point>(cx)
+            .into_iter()
+            .map(|selection| selection.start..selection.end)
+            .collect::<Vec<_>>();
+        self.unfold_ranges(&selections, true, true, cx);
+
         let mut new_selection_ranges = Vec::new();
         {
-            let selections = self.selections.all::<Point>(cx);
             let buffer = self.buffer.read(cx).read(cx);
             for selection in selections {
                 for row in selection.start.row..selection.end.row {
                     let cursor = Point::new(row, buffer.line_len(MultiBufferRow(row)));
                     new_selection_ranges.push(cursor..cursor);
                 }
+
+                let is_multiline_selection = selection.start.row != selection.end.row;
+                // Don't insert last one if it's a multi-line selection ending at the start of a line,
+                // so this action feels more ergonomic when paired with other selection operations
+                let should_skip_last = is_multiline_selection && selection.end.column == 0;
+                if !should_skip_last {
                     new_selection_ranges.push(selection.end..selection.end);
-                to_unfold.push(selection.start..selection.end);
                 }
             }
-        self.unfold_ranges(&to_unfold, true, true, cx);
+        }
         self.change_selections(Some(Autoscroll::fit()), window, cx, |s| {
             s.select_ranges(new_selection_ranges);
         });

crates/editor/src/editor_tests.rs

@@ -4874,13 +4874,76 @@ fn test_select_line(cx: &mut TestAppContext) {
 }
 
 #[gpui::test]
-fn test_split_selection_into_lines(cx: &mut TestAppContext) {
+async fn test_split_selection_into_lines(cx: &mut TestAppContext) {
+    init_test(cx, |_| {});
+    let mut cx = EditorTestContext::new(cx).await;
+
+    #[track_caller]
+    fn test(cx: &mut EditorTestContext, initial_state: &'static str, expected_state: &'static str) {
+        cx.set_state(initial_state);
+        cx.update_editor(|e, window, cx| {
+            e.split_selection_into_lines(&SplitSelectionIntoLines, window, cx)
+        });
+        cx.assert_editor_state(expected_state);
+    }
+
+    // Selection starts and ends at the middle of lines, left-to-right
+    test(
+        &mut cx,
+        "aa\nb«ˇb\ncc\ndd\ne»e\nff",
+        "aa\nbbˇ\nccˇ\nddˇ\neˇe\nff",
+    );
+    // Same thing, right-to-left
+    test(
+        &mut cx,
+        "aa\nb«b\ncc\ndd\neˇ»e\nff",
+        "aa\nbbˇ\nccˇ\nddˇ\neˇe\nff",
+    );
+
+    // Whole buffer, left-to-right, last line *doesn't* end with newline
+    test(
+        &mut cx,
+        "«ˇaa\nbb\ncc\ndd\nee\nff»",
+        "aaˇ\nbbˇ\nccˇ\nddˇ\neeˇ\nffˇ",
+    );
+    // Same thing, right-to-left
+    test(
+        &mut cx,
+        "«aa\nbb\ncc\ndd\nee\nffˇ»",
+        "aaˇ\nbbˇ\nccˇ\nddˇ\neeˇ\nffˇ",
+    );
+
+    // Whole buffer, left-to-right, last line ends with newline
+    test(
+        &mut cx,
+        "«ˇaa\nbb\ncc\ndd\nee\nff\n»",
+        "aaˇ\nbbˇ\nccˇ\nddˇ\neeˇ\nffˇ\n",
+    );
+    // Same thing, right-to-left
+    test(
+        &mut cx,
+        "«aa\nbb\ncc\ndd\nee\nff\nˇ»",
+        "aaˇ\nbbˇ\nccˇ\nddˇ\neeˇ\nffˇ\n",
+    );
+
+    // Starts at the end of a line, ends at the start of another
+    test(
+        &mut cx,
+        "aa\nbb«ˇ\ncc\ndd\nee\n»ff\n",
+        "aa\nbbˇ\nccˇ\nddˇ\neeˇ\nff\n",
+    );
+}
+
+#[gpui::test]
+async fn test_split_selection_into_lines_interacting_with_creases(cx: &mut TestAppContext) {
     init_test(cx, |_| {});
 
     let editor = cx.add_window(|window, cx| {
         let buffer = MultiBuffer::build_simple(&sample_text(9, 5, 'a'), cx);
         build_editor(buffer, window, cx)
     });
+
+    // setup
     _ = editor.update(cx, |editor, window, cx| {
         editor.fold_creases(
             vec![
@@ -4892,6 +4955,13 @@ fn test_split_selection_into_lines(cx: &mut TestAppContext) {
             window,
             cx,
         );
+        assert_eq!(
+            editor.display_text(cx),
+            "aa⋯bbb\nccc⋯eeee\nfffff\nggggg\n⋯i"
+        );
+    });
+
+    _ = editor.update(cx, |editor, window, cx| {
         editor.change_selections(None, window, cx, |s| {
             s.select_display_ranges([
                 DisplayPoint::new(DisplayRow(0), 0)..DisplayPoint::new(DisplayRow(0), 1),
@@ -4900,28 +4970,15 @@ fn test_split_selection_into_lines(cx: &mut TestAppContext) {
                 DisplayPoint::new(DisplayRow(4), 4)..DisplayPoint::new(DisplayRow(4), 4),
             ])
         });
-        assert_eq!(
-            editor.display_text(cx),
-            "aa⋯bbb\nccc⋯eeee\nfffff\nggggg\n⋯i"
-        );
-    });
-
-    _ = editor.update(cx, |editor, window, cx| {
         editor.split_selection_into_lines(&SplitSelectionIntoLines, window, cx);
         assert_eq!(
             editor.display_text(cx),
             "aaaaa\nbbbbb\nccc⋯eeee\nfffff\nggggg\n⋯i"
         );
-        assert_eq!(
-            editor.selections.display_ranges(cx),
-            [
-                DisplayPoint::new(DisplayRow(0), 1)..DisplayPoint::new(DisplayRow(0), 1),
-                DisplayPoint::new(DisplayRow(0), 2)..DisplayPoint::new(DisplayRow(0), 2),
-                DisplayPoint::new(DisplayRow(2), 0)..DisplayPoint::new(DisplayRow(2), 0),
-                DisplayPoint::new(DisplayRow(5), 4)..DisplayPoint::new(DisplayRow(5), 4)
-            ]
-        );
     });
+    EditorTestContext::for_editor(editor, cx)
+        .await
+        .assert_editor_state("aˇaˇaaa\nbbbbb\nˇccccc\nddddd\neeeee\nfffff\nggggg\nhhhhh\niiiiiˇ");
 
     _ = editor.update(cx, |editor, window, cx| {
         editor.change_selections(None, window, cx, |s| {
@@ -4943,11 +5000,15 @@ fn test_split_selection_into_lines(cx: &mut TestAppContext) {
                 DisplayPoint::new(DisplayRow(3), 5)..DisplayPoint::new(DisplayRow(3), 5),
                 DisplayPoint::new(DisplayRow(4), 5)..DisplayPoint::new(DisplayRow(4), 5),
                 DisplayPoint::new(DisplayRow(5), 5)..DisplayPoint::new(DisplayRow(5), 5),
-                DisplayPoint::new(DisplayRow(6), 5)..DisplayPoint::new(DisplayRow(6), 5),
+                DisplayPoint::new(DisplayRow(6), 5)..DisplayPoint::new(DisplayRow(6), 5)
-                DisplayPoint::new(DisplayRow(7), 0)..DisplayPoint::new(DisplayRow(7), 0)
             ]
         );
     });
+    EditorTestContext::for_editor(editor, cx)
+        .await
+        .assert_editor_state(
+            "aaaaaˇ\nbbbbbˇ\ncccccˇ\ndddddˇ\neeeeeˇ\nfffffˇ\ngggggˇ\nhhhhh\niiiii",
+        );
 }
 
 #[gpui::test]
@@ -4956,7 +5017,6 @@ async fn test_add_selection_above_below(cx: &mut TestAppContext) {
 
     let mut cx = EditorTestContext::new(cx).await;
 
-    // let buffer = MultiBuffer::build_simple("abc\ndefghi\n\njk\nlmno\n", cx);
     cx.set_state(indoc!(
         r#"abc
            defˇghi

crates/rope/src/rope.rs

@@ -975,7 +975,10 @@ pub struct TextSummary {
     pub chars: usize,
     /// Length in UTF-16 code units
     pub len_utf16: OffsetUtf16,
-    /// A point representing the number of lines and the length of the last line
+    /// A point representing the number of lines and the length of the last line.
+    ///
+    /// In other words, it marks the point after the last byte in the text, (if
+    /// EOF was a character, this would be its position).
     pub lines: Point,
     /// How many `char`s are in the first line
     pub first_line_chars: u32,