Allow null values for definiens_node

tree-sitter-stack-graphs/src/lib.rs

@@ -187,6 +187,8 @@
 //! }
 //! ```
 //!
+//! Definiens are optional and setting them to `#null` explicitly is allowed.
+//!
 //! ### Connecting stack graph nodes with edges
 //!
 //! To connect two stack graph nodes, use the `edge` statement to add an edge between them:
@@ -1165,6 +1167,7 @@ impl<'a> Builder<'a> {
     ) -> Result<(), BuildError> {
         let node = &self.graph[node_ref];
         let definiens_node = match node.attributes.get(DEFINIENS_NODE) {
+            Some(Value::Null) => return Ok(()),
             Some(definiens_node) => &self.graph[definiens_node.as_syntax_node_ref()?],
             None => return Ok(()),
         };

tree-sitter-stack-graphs/tests/it/nodes.rs

@@ -313,6 +313,26 @@ fn can_set_definiens() {
     assert_eq!("2:8-2:12", actual_span)
 }
 
+#[test]
+fn can_set_null_definiens() {
+    let tsg = r#"
+      (function_definition name:(_)@name) {
+         node result
+         attr (result) type = "pop_symbol", symbol = (source-text @name), source_node = @name, is_definition
+         attr (result) definiens_node = #null
+      }
+    "#;
+    let python = r#"
+      def foo():
+        pass
+    "#;
+
+    let (graph, file) = build_stack_graph(python, tsg).unwrap();
+    let node_handle = graph.nodes_for_file(file).next().unwrap();
+    let source_info = graph.source_info(node_handle).unwrap();
+    assert_eq!(lsp_positions::Span::default(), source_info.definiens_span)
+}
+
 #[test]
 fn can_set_syntax_type() {
     let tsg = r#"