Merge pull request #1109 from nhasabni/nhasabni/ts_node_child_field_name

Adding API to get field name of a TSNode

cli/src/tests/node_test.rs

@@ -248,6 +248,31 @@ fn test_node_parent_of_child_by_field_name() {
     );
 }
 
+#[test]
+fn test_node_field_name_for_child() {
+    let mut parser = Parser::new();
+    parser.set_language(get_language("c")).unwrap();
+    let tree = parser.parse("x + y;", None).unwrap();
+    let translation_unit_node = tree.root_node();
+    let binary_expression_node = translation_unit_node
+        .named_child(0)
+        .unwrap()
+        .named_child(0)
+        .unwrap();
+
+    assert_eq!(binary_expression_node.field_name_for_child(0), Some("left"));
+    assert_eq!(
+        binary_expression_node.field_name_for_child(1),
+        Some("operator")
+    );
+    assert_eq!(
+        binary_expression_node.field_name_for_child(2),
+        Some("right")
+    );
+    // Negative test - Not a valid child index
+    assert_eq!(binary_expression_node.field_name_for_child(3), None);
+}
+
 #[test]
 fn test_node_child_by_field_name_with_extra_hidden_children() {
     let mut parser = Parser::new();

lib/binding_rust/bindings.rs

@@ -434,6 +434,11 @@ extern "C" {
     #[doc = " child."]
     pub fn ts_node_child(arg1: TSNode, arg2: u32) -> TSNode;
 }
+extern "C" {
+    #[doc = " Get the field name for node's child at the given index, where zero represents"]
+    #[doc = " the first child. Returns NULL, if no field is found."]
+    pub fn ts_node_field_name_for_child(arg1: TSNode, arg2: u32) -> *const ::std::os::raw::c_char;
+}
 extern "C" {
     #[doc = " Get the node\'s number of children."]
     pub fn ts_node_child_count(arg1: TSNode) -> u32;

lib/binding_rust/lib.rs

@@ -859,6 +859,18 @@ impl<'tree> Node<'tree> {
         Self::new(unsafe { ffi::ts_node_child_by_field_id(self.0, field_id) })
     }
 
+    /// Get the field name of this node's child at the given index.
+    pub fn field_name_for_child(&self, child_index: u32) -> Option<&'static str> {
+        unsafe {
+            let ptr = ffi::ts_node_field_name_for_child(self.0, child_index);
+            if ptr.is_null() {
+                None
+            } else {
+                Some(CStr::from_ptr(ptr).to_str().unwrap())
+            }
+        }
+    }
+
     /// Iterate over this node's children.
     ///
     /// A [TreeCursor] is used to retrieve the children efficiently. Obtain

lib/include/tree_sitter/api.h

@@ -487,6 +487,12 @@ TSNode ts_node_parent(TSNode);
  */
 TSNode ts_node_child(TSNode, uint32_t);
 
+/**
+ * Get the field name for node's child at the given index, where zero represents
+ * the first child. Returns NULL, if no field is found.
+ */
+const char *ts_node_field_name_for_child(TSNode, uint32_t);
+
 /**
  * Get the node's number of children.
  */

lib/src/node.c

@@ -569,6 +569,23 @@ recur:
   return ts_node__null();
 }
 
+const char *ts_node_field_name_for_child(TSNode self, uint32_t child_index) {
+  const TSFieldMapEntry *field_map_start = NULL, *field_map_end = NULL;
+  ts_language_field_map(
+    self.tree->language,
+    ts_node__subtree(self).ptr->production_id,
+    &field_map_start,
+    &field_map_end
+  );
+
+  for (const TSFieldMapEntry *i = field_map_start; i < field_map_end; i++) {
+    if (i->child_index == child_index) {
+      return self.tree->language->field_names[i->field_id];
+    }
+  }
+  return NULL;
+}
+
 TSNode ts_node_child_by_field_name(
   TSNode self,
   const char *name,