Allow capturing multiple nodes in textobject queries

Treesitter captures can contain multiple nodes like so:

```
(line_comment)+ @comment
```

This would match each line in a comment as a separate
`@comment` capture when what we actually want is the
whole set of contiguous `line_comment` nodes to be
captured under the `@comment` capture. This commit enables
this behaviour.

helix-core/src/syntax.rs

@@ -244,16 +244,55 @@ pub struct TextObjectQuery {
     pub query: Query,
 }
 
+pub enum CapturedNode<'a> {
+    Single(Node<'a>),
+    Grouped(Vec<Node<'a>>),
+}
+
+impl<'a> CapturedNode<'a> {
+    pub fn start_byte(&self) -> usize {
+        match self {
+            Self::Single(n) => n.start_byte(),
+            Self::Grouped(ns) => ns[0].start_byte(),
+        }
+    }
+
+    pub fn end_byte(&self) -> usize {
+        match self {
+            Self::Single(n) => n.end_byte(),
+            Self::Grouped(ns) => ns.last().unwrap().end_byte(),
+        }
+    }
+
+    pub fn byte_range(&self) -> std::ops::Range<usize> {
+        self.start_byte()..self.end_byte()
+    }
+}
+
 impl TextObjectQuery {
     /// Run the query on the given node and return sub nodes which match given
     /// capture ("function.inside", "class.around", etc).
+    ///
+    /// Captures may contain multiple nodes by using quantifiers (+, *, etc),
+    /// and support for this is partial and could use improvement.
+    ///
+    /// ```query
+    /// ;; supported:
+    /// (comment)+ @capture
+    ///
+    /// ;; unsupported:
+    /// (
+    ///   (comment)+
+    ///   (function)
+    /// ) @capture
+    /// ```
     pub fn capture_nodes<'a>(
         &'a self,
         capture_name: &str,
         node: Node<'a>,
         slice: RopeSlice<'a>,
         cursor: &'a mut QueryCursor,
-    ) -> Option<impl Iterator<Item = Node<'a>>> {
+    ) -> Option<impl Iterator<Item = CapturedNode<'a>>> {
         self.capture_nodes_any(&[capture_name], node, slice, cursor)
     }
 
@@ -265,17 +304,28 @@ impl TextObjectQuery {
         node: Node<'a>,
         slice: RopeSlice<'a>,
         cursor: &'a mut QueryCursor,
-    ) -> Option<impl Iterator<Item = Node<'a>>> {
+    ) -> Option<impl Iterator<Item = CapturedNode<'a>>> {
         let capture_idx = capture_names
             .iter()
             .find_map(|cap| self.query.capture_index_for_name(cap))?;
-        let captures = cursor.captures(&self.query, node, RopeProvider(slice));
+        let captures = cursor.matches(&self.query, node, RopeProvider(slice));
 
-        captures
-            .filter_map(move |(mat, idx)| {
-                (mat.captures[idx].index == capture_idx).then(|| mat.captures[idx].node)
-            })
-            .into()
+        let nodes = captures.flat_map(move |mat| {
+            let captures = mat.captures.iter().filter(move |c| c.index == capture_idx);
+            let nodes = captures.map(|c| c.node);
+            let pattern_idx = mat.pattern_index;
+            let quantifier = self.query.capture_quantifiers(pattern_idx)[capture_idx as usize];
+
+            let iter: Box<dyn Iterator<Item = CapturedNode>> = match quantifier {
+                CaptureQuantifier::OneOrMore | CaptureQuantifier::ZeroOrMore => {
+                    Box::new(std::iter::once(CapturedNode::Grouped(nodes.collect())))
+                }
+                _ => Box::new(nodes.map(CapturedNode::Single)),
+            };
+
+            iter
+        });
+        Some(nodes)
     }
 }
 
@@ -1075,8 +1125,8 @@ pub(crate) fn generate_edits(
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::{iter, mem, ops, str, usize};
 use tree_sitter::{
-    Language as Grammar, Node, Parser, Point, Query, QueryCaptures, QueryCursor, QueryError,
-    QueryMatch, Range, TextProvider, Tree,
+    CaptureQuantifier, Language as Grammar, Node, Parser, Point, Query, QueryCaptures, QueryCursor,
+    QueryError, QueryMatch, Range, TextProvider, Tree,
 };
 
 const CANCELLATION_CHECK_INTERVAL: usize = 100;
@@ -1928,6 +1978,50 @@ mod test {
     use super::*;
     use crate::{Rope, Transaction};
 
+    #[test]
+    fn test_textobject_queries() {
+        let query_str = r#"
+        (line_comment)+ @quantified_nodes
+        ((line_comment)+) @quantified_nodes_grouped
+        ((line_comment) (line_comment)) @multiple_nodes_grouped
+        "#;
+        let source = Rope::from_str(
+            r#"
+/// a comment on
+/// mutiple lines
+        "#,
+        );
+
+        let loader = Loader::new(Configuration { language: vec![] });
+        let language = get_language(&crate::RUNTIME_DIR, "Rust").unwrap();
+
+        let query = Query::new(language, query_str).unwrap();
+        let textobject = TextObjectQuery { query };
+        let mut cursor = QueryCursor::new();
+
+        let config = HighlightConfiguration::new(language, "", "", "").unwrap();
+        let syntax = Syntax::new(&source, Arc::new(config), Arc::new(loader));
+
+        let root = syntax.tree().root_node();
+        let mut test = |capture, range| {
+            let matches: Vec<_> = textobject
+                .capture_nodes(capture, root, source.slice(..), &mut cursor)
+                .unwrap()
+                .collect();
+
+            assert_eq!(
+                matches[0].byte_range(),
+                range,
+                "@{capture} expected {range:?}"
+            )
+        };
+
+        test("quantified_nodes", 1..35);
+        // NOTE: Enable after implementing proper node group capturing
+        // test("quantified_nodes_grouped", 1..35);
+        // test("multiple_nodes_grouped", 1..35);
+    }
+
     #[test]
     fn test_parser() {
         let highlight_names: Vec<String> = [