Start work on auto-indenting lines on tab

Co-authored-by: Julia Risley <floc@unpromptedtirade.com>

crates/editor/src/editor.rs

@@ -2913,8 +2913,80 @@ impl Editor {
             return;
         }
 
-        let mut selections = self.selections.all_adjusted(cx);
-        if selections.iter().all(|s| s.is_empty()) {
+        let selections = self.selections.all_adjusted(cx);
+        let buffer = self.buffer.read(cx).read(cx);
+        let suggested_indents =
+            buffer.suggested_indents(selections.iter().map(|s| s.head().row), cx);
+        let mut all_selections_empty = true;
+        let mut all_cursors_before_suggested_indent = true;
+        let mut all_cursors_in_leading_whitespace = true;
+
+        for selection in &selections {
+            let cursor = selection.head();
+            if !selection.is_empty() {
+                all_selections_empty = false;
+            }
+            if cursor.column > buffer.indent_size_for_line(cursor.row).len {
+                all_cursors_in_leading_whitespace = false;
+            }
+            if let Some(indent) = suggested_indents.get(&cursor.row) {
+                if cursor.column >= indent.len {
+                    all_cursors_before_suggested_indent = false;
+                }
+            } else {
+                all_cursors_before_suggested_indent = false;
+            }
+        }
+        drop(buffer);
+
+        if all_selections_empty {
+            if all_cursors_in_leading_whitespace && all_cursors_before_suggested_indent {
+                self.auto_indent(suggested_indents, selections, cx);
+            } else {
+                self.insert_tab(selections, cx);
+            }
+        } else {
+            self.indent(&Indent, cx);
+        }
+    }
+
+    fn auto_indent(
+        &mut self,
+        suggested_indents: BTreeMap<u32, IndentSize>,
+        mut selections: Vec<Selection<Point>>,
+        cx: &mut ViewContext<Editor>,
+    ) {
+        self.transact(cx, |this, cx| {
+            let mut rows = Vec::new();
+            let buffer = this.buffer.read(cx).read(cx);
+            for selection in &mut selections {
+                selection.end.column = buffer.indent_size_for_line(selection.end.row).len;
+                selection.start = selection.end;
+                rows.push(selection.end.row);
+            }
+            drop(buffer);
+
+            this.change_selections(Some(Autoscroll::Fit), cx, |s| {
+                s.select(selections);
+            });
+
+            this.buffer.update(cx, |buffer, cx| {
+                let snapshot = buffer.read(cx);
+                let edits: Vec<_> = suggested_indents
+                    .into_iter()
+                    .filter_map(|(row, new_indent)| {
+                        let current_indent = snapshot.indent_size_for_line(row);
+                        Buffer::edit_for_indent_size_adjustment(row, current_indent, new_indent)
+                    })
+                    .collect();
+                drop(snapshot);
+
+                buffer.edit(edits, None, cx);
+            });
+        });
+    }
+
+    fn insert_tab(&mut self, mut selections: Vec<Selection<Point>>, cx: &mut ViewContext<Editor>) {
         self.transact(cx, |this, cx| {
             this.buffer.update(cx, |buffer, cx| {
                 let mut prev_cursor_row = 0;
@@ -2941,6 +3013,7 @@ impl Editor {
                         let chars_to_next_tab_stop = tab_size - (char_column as u32 % tab_size);
                         IndentSize::spaces(chars_to_next_tab_stop)
                     };
+
                     buffer.edit(
                         [(cursor..cursor, tab_size.chars().collect::<String>())],
                         None,
@@ -2957,9 +3030,6 @@ impl Editor {
                 s.select(selections);
             });
         });
-        } else {
-            self.indent(&Indent, cx);
-        }
     }
 
     pub fn indent(&mut self, _: &Indent, cx: &mut ViewContext<Self>) {
@@ -7966,6 +8036,56 @@ mod tests {
         "});
     }
 
+    #[gpui::test]
+    async fn test_tab_on_blank_line_auto_indents(cx: &mut gpui::TestAppContext) {
+        let mut cx = EditorTestContext::new(cx).await;
+        let language = Arc::new(
+            Language::new(
+                LanguageConfig::default(),
+                Some(tree_sitter_rust::language()),
+            )
+            .with_indents_query(r#"(_ "(" ")" @end) @indent"#)
+            .unwrap(),
+        );
+        cx.update_buffer(|buffer, cx| buffer.set_language(Some(language), cx));
+        cx.set_state(indoc! {"
+            const a: B = (
+                c(
+                    d(
+            |
+                    )
+            |
+                )
+            );
+        "});
+
+        // autoindent when one or more cursor is to the left of the correct level.
+        cx.update_editor(|e, cx| e.tab(&Tab, cx));
+        cx.assert_editor_state(indoc! {"
+            const a: B = (
+                c(
+                    d(
+                        |
+                    )
+                    |
+                )
+            );
+        "});
+
+        // when already at the correct indentation level, insert a tab.
+        cx.update_editor(|e, cx| e.tab(&Tab, cx));
+        cx.assert_editor_state(indoc! {"
+            const a: B = (
+                c(
+                    d(
+                            |
+                    )
+                        |
+                )
+            );
+        "});
+    }
+
     #[gpui::test]
     async fn test_indent_outdent(cx: &mut gpui::TestAppContext) {
         let mut cx = EditorTestContext::new(cx).await;

crates/editor/src/multi_buffer.rs

@@ -3,7 +3,7 @@ mod anchor;
 pub use anchor::{Anchor, AnchorRangeExt};
 use anyhow::Result;
 use clock::ReplicaId;
-use collections::{Bound, HashMap, HashSet};
+use collections::{BTreeMap, Bound, HashMap, HashSet};
 use gpui::{AppContext, Entity, ModelContext, ModelHandle, Task};
 pub use language::Completion;
 use language::{
@@ -1939,6 +1939,53 @@ impl MultiBufferSnapshot {
         }
     }
 
+    pub fn suggested_indents(
+        &self,
+        rows: impl IntoIterator<Item = u32>,
+        cx: &AppContext,
+    ) -> BTreeMap<u32, IndentSize> {
+        let mut result = BTreeMap::new();
+
+        let mut rows_for_excerpt = Vec::new();
+        let mut cursor = self.excerpts.cursor::<Point>();
+
+        let mut rows = rows.into_iter().peekable();
+        while let Some(row) = rows.next() {
+            cursor.seek(&Point::new(row, 0), Bias::Right, &());
+            let excerpt = match cursor.item() {
+                Some(excerpt) => excerpt,
+                _ => continue,
+            };
+
+            let single_indent_size = excerpt.buffer.single_indent_size(cx);
+            let start_buffer_row = excerpt.range.context.start.to_point(&excerpt.buffer).row;
+            let start_multibuffer_row = cursor.start().row;
+
+            rows_for_excerpt.push(row);
+            while let Some(next_row) = rows.peek().copied() {
+                if cursor.end(&()).row > next_row {
+                    rows_for_excerpt.push(next_row);
+                    rows.next();
+                } else {
+                    break;
+                }
+            }
+
+            let buffer_rows = rows_for_excerpt
+                .drain(..)
+                .map(|row| start_buffer_row + row - start_multibuffer_row);
+            let buffer_indents = excerpt
+                .buffer
+                .suggested_indents(buffer_rows, single_indent_size);
+            let multibuffer_indents = buffer_indents
+                .into_iter()
+                .map(|(row, indent)| (start_multibuffer_row + row - start_buffer_row, indent));
+            result.extend(multibuffer_indents);
+        }
+
+        result
+    }
+
     pub fn indent_size_for_line(&self, row: u32) -> IndentSize {
         if let Some((buffer, range)) = self.buffer_line_for_row(row) {
             let mut size = buffer.indent_size_for_line(range.start.row);

crates/language/src/buffer.rs

@@ -957,45 +957,42 @@ impl Buffer {
         cx: &mut ModelContext<Self>,
     ) {
         self.autoindent_requests.clear();
-        self.start_transaction();
-        for (row, indent_size) in &indent_sizes {
-            self.set_indent_size_for_line(*row, *indent_size, cx);
-        }
-        self.end_transaction(cx);
-    }
 
-    fn set_indent_size_for_line(
-        &mut self,
-        row: u32,
-        size: IndentSize,
-        cx: &mut ModelContext<Self>,
-    ) {
+        let edits: Vec<_> = indent_sizes
+            .into_iter()
+            .filter_map(|(row, indent_size)| {
                 let current_size = indent_size_for_line(&self, row);
-        if size.kind != current_size.kind && current_size.len > 0 {
-            return;
+                Self::edit_for_indent_size_adjustment(row, current_size, indent_size)
+            })
+            .collect();
+
+        self.edit(edits, None, cx);
     }
 
-        if size.len > current_size.len {
-            let offset = Point::new(row, 0).to_offset(&*self);
-            self.edit(
-                [(
-                    offset..offset,
-                    iter::repeat(size.char())
-                        .take((size.len - current_size.len) as usize)
+    pub fn edit_for_indent_size_adjustment(
+        row: u32,
+        current_size: IndentSize,
+        new_size: IndentSize,
+    ) -> Option<(Range<Point>, String)> {
+        if new_size.kind != current_size.kind && current_size.len > 0 {
+            return None;
+        }
+
+        if new_size.len > current_size.len {
+            let point = Point::new(row, 0);
+            Some((
+                point..point,
+                iter::repeat(new_size.char())
+                    .take((new_size.len - current_size.len) as usize)
                     .collect::<String>(),
-                )],
-                None,
-                cx,
-            );
-        } else if size.len < current_size.len {
-            self.edit(
-                [(
-                    Point::new(row, 0)..Point::new(row, current_size.len - size.len),
-                    "",
-                )],
-                None,
-                cx,
-            );
+            ))
+        } else if new_size.len < current_size.len {
+            Some((
+                Point::new(row, 0)..Point::new(row, current_size.len - new_size.len),
+                String::new(),
+            ))
+        } else {
+            None
         }
     }
 
@@ -1225,13 +1222,7 @@ impl Buffer {
         let edit_id = edit_operation.local_timestamp();
 
         if let Some((before_edit, mode)) = autoindent_request {
-            let language_name = self.language().map(|language| language.name());
-            let settings = cx.global::<Settings>();
-            let indent_size = if settings.hard_tabs(language_name.as_deref()) {
-                IndentSize::tab()
-            } else {
-                IndentSize::spaces(settings.tab_size(language_name.as_deref()).get())
-            };
+            let indent_size = before_edit.single_indent_size(cx);
             let (start_columns, is_block_mode) = match mode {
                 AutoindentMode::Block {
                     original_indent_columns: start_columns,
@@ -1611,6 +1602,47 @@ impl BufferSnapshot {
         indent_size_for_line(&self, row)
     }
 
+    pub fn single_indent_size(&self, cx: &AppContext) -> IndentSize {
+        let language_name = self.language().map(|language| language.name());
+        let settings = cx.global::<Settings>();
+        if settings.hard_tabs(language_name.as_deref()) {
+            IndentSize::tab()
+        } else {
+            IndentSize::spaces(settings.tab_size(language_name.as_deref()).get())
+        }
+    }
+
+    pub fn suggested_indents(
+        &self,
+        rows: impl Iterator<Item = u32>,
+        single_indent_size: IndentSize,
+    ) -> BTreeMap<u32, IndentSize> {
+        let mut result = BTreeMap::new();
+
+        for row_range in contiguous_ranges(rows, 10) {
+            let suggestions = match self.suggest_autoindents(row_range.clone()) {
+                Some(suggestions) => suggestions,
+                _ => break,
+            };
+
+            for (row, suggestion) in row_range.zip(suggestions) {
+                let indent_size = if let Some(suggestion) = suggestion {
+                    result
+                        .get(&suggestion.basis_row)
+                        .copied()
+                        .unwrap_or_else(|| self.indent_size_for_line(suggestion.basis_row))
+                        .with_delta(suggestion.delta, single_indent_size)
+                } else {
+                    self.indent_size_for_line(row)
+                };
+
+                result.insert(row, indent_size);
+            }
+        }
+
+        result
+    }
+
     fn suggest_autoindents<'a>(
         &'a self,
         row_range: Range<u32>,