Add SyntaxNode::lookup_position (#5562)

crates/cairo-lang-language-server/src/lib.rs

@@ -1116,11 +1116,8 @@ fn get_node_and_lookup_items(
     file: FileId,
     position: TextPosition,
 ) -> Option<(SyntaxNode, Vec<LookupItemId>)> {
-    // Find offset for position.
-    let offset = position.offset_in_file(db.upcast(), file)?;
-
     // Find the most specific syntax node at the offset.
-    let node = db.file_syntax(file).to_option()?.lookup_offset(db.upcast(), offset);
+    let node = db.file_syntax(file).to_option()?.lookup_position(db.upcast(), position);
 
     // Find module.
     let module_id = find_node_module(db, file, node.clone()).on_none(|| {

crates/cairo-lang-syntax/src/node/mod.rs

@@ -3,7 +3,7 @@ use std::fmt::Display;
 use std::sync::Arc;
 
 use cairo_lang_filesystem::ids::FileId;
-use cairo_lang_filesystem::span::{TextOffset, TextSpan, TextWidth};
+use cairo_lang_filesystem::span::{TextOffset, TextPosition, TextSpan, TextWidth};
 use cairo_lang_utils::{require, Intern, LookupIntern};
 use smol_str::SmolStr;
 
@@ -158,6 +158,14 @@ impl SyntaxNode {
         self.clone()
     }
 
+    /// Lookups a syntax node using a position.
+    pub fn lookup_position(&self, db: &dyn SyntaxGroup, position: TextPosition) -> SyntaxNode {
+        match position.offset_in_file(db.upcast(), self.stable_ptr().file_id(db)) {
+            Some(offset) => self.lookup_offset(db, offset),
+            None => self.clone(),
+        }
+    }
+
     /// Returns all the text under the syntax node.
     /// Note that this traverses the syntax tree, and generates a new string, so use responsibly.
     pub fn get_text(&self, db: &dyn SyntaxGroup) -> String {