editor: Fix auto indent adding trailing whitespace on repeated enter (#52628)

Gonçalo Aleixo and dino created 1 week ago

Update how auto indentation is handled by `Editor::newline`, in the case
where auto-indentation is not `AutoIndentationMode::None`, so as to
extend the range of the edits being applied to the beginning of the
line, in case the line only contains the indentation whitespace or
there's only whitespace indentation before the cursor position

This ensures that newlines are not left with whitespace.

Closes #34316 

Release Notes:

- Fixed auto indent leaving trailing whitespace on blank indented lines
when creating new lines.⁠

---------

Co-authored-by: dino <[e-mail]>

Change summary

crates/editor/src/editor.rs       | 16 ++++++
crates/editor/src/editor_tests.rs | 75 +++++++++++++++++++++++++++++++++
2 files changed, 90 insertions(+), 1 deletion(-)

Detailed changes

crates/editor/src/editor.rs

@@ -5303,8 +5303,9 @@ impl Editor {
                         let start_point = selection.start.to_point(&buffer);
                         let mut existing_indent =
                             buffer.indent_size_for_line(MultiBufferRow(start_point.row));
+                        let full_indent_len = existing_indent.len;
                         existing_indent.len = cmp::min(existing_indent.len, start_point.column);
-                        let start = selection.start;
+                        let mut start = selection.start;
                         let end = selection.end;
                         let selection_is_empty = start == end;
                         let language_scope = buffer.language_scope_at(start);
@@ -5454,6 +5455,19 @@ impl Editor {
                                     }
                                     new_text.extend(extra_indent.chars());
                                 }
+                                // Extend the edit to the beginning of the line
+                                // to clear auto-indent whitespace that would
+                                // otherwise remain as trailing whitespace. This
+                                // applies to blank lines and lines where only
+                                // indentation remains before the cursor.
+                                if selection_is_empty
+                                    && preserve_indent
+                                    && full_indent_len > 0
+                                    && start_point.column == full_indent_len
+                                {
+                                    start = buffer.point_to_offset(Point::new(start_point.row, 0));
+                                }
+
                                 (
                                     start,
                                     new_text,

crates/editor/src/editor_tests.rs

@@ -3553,6 +3553,81 @@ fn test_newline(cx: &mut TestAppContext) {
     });
 }
 
+#[gpui::test]
+fn test_newline_trailing_whitespace(cx: &mut TestAppContext) {
+    init_test(cx, |settings| {
+        settings.defaults.auto_indent = Some(settings::AutoIndentMode::PreserveIndent);
+    });
+
+    let buffer = cx.update(|cx| MultiBuffer::build_simple("    hello\n    world\n", cx));
+    let editor = cx.add_window(|window, cx| build_editor(buffer.clone(), window, cx));
+
+    editor
+        .update(cx, |editor, window, cx| {
+            editor.change_selections(SelectionEffects::no_scroll(), window, cx, |s| {
+                s.select_display_ranges([
+                    DisplayPoint::new(DisplayRow(0), 9)..DisplayPoint::new(DisplayRow(0), 9)
+                ])
+            });
+
+            editor.newline(&Newline, window, cx);
+            assert_eq!(editor.text(cx), "    hello\n    \n    world\n");
+
+            editor.newline(&Newline, window, cx);
+            assert_eq!(editor.text(cx), "    hello\n\n    \n    world\n");
+        })
+        .unwrap();
+
+    buffer.update(cx, |buffer, cx| {
+        let start = MultiBufferOffset(0);
+        let end = buffer.len(cx);
+        buffer.edit([(start..end, "    hello\n    world\n")], None, cx);
+    });
+
+    editor
+        .update(cx, |editor, window, cx| {
+            editor.change_selections(SelectionEffects::no_scroll(), window, cx, |s| {
+                s.select_display_ranges([
+                    DisplayPoint::new(DisplayRow(0), 7)..DisplayPoint::new(DisplayRow(0), 7)
+                ])
+            });
+
+            editor.newline(&Newline, window, cx);
+            assert_eq!(editor.text(cx), "    hel\n    lo\n    world\n");
+
+            editor.newline(&Newline, window, cx);
+            assert_eq!(editor.text(cx), "    hel\n\n    lo\n    world\n");
+        })
+        .unwrap();
+
+    update_test_language_settings(cx, &|settings| {
+        settings.defaults.tab_size = NonZeroU32::new(4);
+        settings.defaults.hard_tabs = Some(true);
+    });
+
+    buffer.update(cx, |buffer, cx| {
+        let start = MultiBufferOffset(0);
+        let end = buffer.len(cx);
+        buffer.edit([(start..end, "\thello\n\tworld\n")], None, cx);
+    });
+
+    editor
+        .update(cx, |editor, window, cx| {
+            editor.change_selections(SelectionEffects::no_scroll(), window, cx, |s| {
+                s.select_display_ranges([
+                    DisplayPoint::new(DisplayRow(0), 9)..DisplayPoint::new(DisplayRow(0), 9)
+                ])
+            });
+
+            editor.newline(&Newline, window, cx);
+            assert_eq!(editor.text(cx), "\thello\n\t\n\tworld\n");
+
+            editor.newline(&Newline, window, cx);
+            assert_eq!(editor.text(cx), "\thello\n\n\t\n\tworld\n");
+        })
+        .unwrap();
+}
+
 #[gpui::test]
 async fn test_newline_yaml(cx: &mut TestAppContext) {
     init_test(cx, |_| {});