feat(commands): shrink_selection

book/src/keymap.md

@@ -261,6 +261,8 @@ Mappings in the style of [vim-unimpaired](https://github.com/tpope/vim-unimpaire
 | `]D`     | Go to last diagnostic in document (**LSP**)  | `goto_last_diag`    |
 | `[space` | Add newline above                            | `add_newline_above` |
 | `]space` | Add newline below                            | `add_newline_below` |
+| `]o`     | Expand syntax tree object selection.         | `expand_selection`  |
+| `[o`     | Shrink syntax tree object selection.         | `shrink_selection`  |
 
 ## Insert Mode
 

helix-core/src/object.rs

@@ -1,7 +1,5 @@
 use crate::{Range, RopeSlice, Selection, Syntax};
 
-// TODO: to contract_selection we'd need to store the previous ranges before expand.
-// Maybe just contract to the first child node?
 pub fn expand_selection(syntax: &Syntax, text: RopeSlice, selection: &Selection) -> Selection {
     let tree = syntax.tree();
 
@@ -34,3 +32,30 @@ pub fn expand_selection(syntax: &Syntax, text: RopeSlice, selection: &Selection)
         }
     })
 }
+
+pub fn shrink_selection(syntax: &Syntax, text: RopeSlice, selection: &Selection) -> Selection {
+    let tree = syntax.tree();
+
+    selection.clone().transform(|range| {
+        let from = text.char_to_byte(range.from());
+        let to = text.char_to_byte(range.to());
+
+        let descendant = match tree.root_node().descendant_for_byte_range(from, to) {
+            // find first child, if not possible, fallback to the node that contains selection
+            Some(descendant) => match descendant.child(0) {
+                Some(child) => child,
+                None => descendant,
+            },
+            None => return range,
+        };
+
+        let from = text.byte_to_char(descendant.start_byte());
+        let to = text.byte_to_char(descendant.end_byte());
+
+        if range.head < range.anchor {
+            Range::new(to, from)
+        } else {
+            Range::new(from, to)
+        }
+    })
+}

helix-core/src/selection.rs

@@ -140,6 +140,11 @@ impl Range {
         self.from() == other.from() || (self.to() > other.from() && other.to() > self.from())
     }
 
+    #[inline]
+    pub fn contains_range(&self, other: &Self) -> bool {
+        self.from() <= other.from() && self.to() >= other.to()
+    }
+
     pub fn contains(&self, pos: usize) -> bool {
         self.from() <= pos && pos < self.to()
     }
@@ -544,6 +549,39 @@ impl Selection {
     pub fn len(&self) -> usize {
         self.ranges.len()
     }
+
+    // returns true if self ⊇ other
+    pub fn contains(&self, other: &Selection) -> bool {
+        // can't contain other if it is larger
+        if other.len() > self.len() {
+            return false;
+        }
+
+        let (mut iter_self, mut iter_other) = (self.iter(), other.iter());
+        let (mut ele_self, mut ele_other) = (iter_self.next(), iter_other.next());
+
+        loop {
+            match (ele_self, ele_other) {
+                (Some(ra), Some(rb)) => {
+                    if !ra.contains_range(rb) {
+                        // `self` doesn't contain next element from `other`, advance `self`, we need to match all from `other`
+                        ele_self = iter_self.next();
+                    } else {
+                        // matched element from `other`, advance `other`
+                        ele_other = iter_other.next();
+                    };
+                }
+                (None, Some(_)) => {
+                    // exhausted `self`, we can't match the reminder of `other`
+                    return false;
+                }
+                (_, None) => {
+                    // no elements from `other` left to match, `self` contains `other`
+                    return true;
+                }
+            }
+        }
+    }
 }
 
 impl<'a> IntoIterator for &'a Selection {
@@ -982,4 +1020,30 @@ mod test {
             &["", "abcd", "efg", "rs", "xyz"]
         );
     }
+    #[test]
+    fn test_selection_contains() {
+        fn contains(a: Vec<(usize, usize)>, b: Vec<(usize, usize)>) -> bool {
+            let sela = Selection::new(a.iter().map(|a| Range::new(a.0, a.1)).collect(), 0);
+            let selb = Selection::new(b.iter().map(|b| Range::new(b.0, b.1)).collect(), 0);
+            sela.contains(&selb)
+        }
+
+        // exact match
+        assert!(contains(vec!((1, 1)), vec!((1, 1))));
+
+        // larger set contains smaller
+        assert!(contains(vec!((1, 1), (2, 2), (3, 3)), vec!((2, 2))));
+
+        // multiple matches
+        assert!(contains(vec!((1, 1), (2, 2)), vec!((1, 1), (2, 2))));
+
+        // smaller set can't contain bigger
+        assert!(!contains(vec!((1, 1)), vec!((1, 1), (2, 2))));
+
+        assert!(contains(
+            vec!((1, 1), (2, 4), (5, 6), (7, 9), (10, 13)),
+            vec!((3, 4), (7, 9))
+        ));
+        assert!(!contains(vec!((1, 1), (5, 6)), vec!((1, 6))));
+    }
 }

helix-term/src/commands.rs

@@ -362,6 +362,7 @@ impl MappableCommand {
         rotate_selection_contents_forward, "Rotate selection contents forward",
         rotate_selection_contents_backward, "Rotate selections contents backward",
         expand_selection, "Expand selection to parent syntax node",
+        shrink_selection, "Shrink selection to previously expanded syntax node",
         jump_forward, "Jump forward on jumplist",
         jump_backward, "Jump backward on jumplist",
         save_selection, "Save the current selection to the jumplist",
@@ -5458,6 +5459,7 @@ fn rotate_selection_contents(cx: &mut Context, direction: Direction) {
     doc.apply(&transaction, view.id);
     doc.append_changes_to_history(view.id);
 }
+
 fn rotate_selection_contents_forward(cx: &mut Context) {
     rotate_selection_contents(cx, Direction::Forward)
 }
@@ -5473,7 +5475,39 @@ fn expand_selection(cx: &mut Context) {
 
         if let Some(syntax) = doc.syntax() {
             let text = doc.text().slice(..);
-            let selection = object::expand_selection(syntax, text, doc.selection(view.id));
+
+            let current_selection = doc.selection(view.id);
+
+            // save current selection so it can be restored using shrink_selection
+            view.object_selections.push(current_selection.clone());
+
+            let selection = object::expand_selection(syntax, text, current_selection);
+            doc.set_selection(view.id, selection);
+        }
+    };
+    motion(cx.editor);
+    cx.editor.last_motion = Some(Motion(Box::new(motion)));
+}
+
+fn shrink_selection(cx: &mut Context) {
+    let motion = |editor: &mut Editor| {
+        let (view, doc) = current!(editor);
+        let current_selection = doc.selection(view.id);
+        // try to restore previous selection
+        if let Some(prev_selection) = view.object_selections.pop() {
+            if current_selection.contains(&prev_selection) {
+                // allow shrinking the selection only if current selection contains the previous object selection
+                doc.set_selection(view.id, prev_selection);
+                return;
+            } else {
+                // clear existing selection as they can't be shrinked to anyway
+                view.object_selections.clear();
+            }
+        }
+        // if not previous selection, shrink to first child
+        if let Some(syntax) = doc.syntax() {
+            let text = doc.text().slice(..);
+            let selection = object::shrink_selection(syntax, text, current_selection);
             doc.set_selection(view.id, selection);
         }
     };

helix-term/src/keymap.rs

@@ -569,11 +569,13 @@ impl Default for Keymaps {
                 "d" => goto_prev_diag,
                 "D" => goto_first_diag,
                 "space" => add_newline_above,
+                "o" => shrink_selection,
             },
             "]" => { "Right bracket"
                 "d" => goto_next_diag,
                 "D" => goto_last_diag,
                 "space" => add_newline_below,
+                "o" => expand_selection,
             },
 
             "/" => search,

helix-view/src/view.rs

@@ -80,6 +80,8 @@ pub struct View {
     // uses two docs because we want to be able to swap between the
     // two last modified docs which we need to manually keep track of
     pub last_modified_docs: [Option<DocumentId>; 2],
+    /// used to store previous selections of tree-sitter objecs
+    pub object_selections: Vec<Selection>,
 }
 
 impl View {
@@ -92,6 +94,7 @@ impl View {
             jumps: JumpList::new((doc, Selection::point(0))), // TODO: use actual sel
             last_accessed_doc: None,
             last_modified_docs: [None, None],
+            object_selections: Vec::new(),
         }
     }