Add serialize, deserialize and reset callbacks to external scanners

Signed-off-by: Nathan Sobo <nathan@github.com>

src/runtime/node.c

@@ -39,7 +39,15 @@ static inline bool ts_node__is_relevant(TSNode self, bool include_anonymous) {
 static inline uint32_t ts_node__relevant_child_count(TSNode self,
                                                    bool include_anonymous) {
   const Tree *tree = ts_node__tree(self);
-  return include_anonymous ? tree->visible_child_count : tree->named_child_count;
+  if (tree->child_count > 0) {
+    if (include_anonymous) {
+      return tree->visible_child_count;
+    } else {
+      return tree->named_child_count;
+    }
+  } else {
+    return 0;
+  }
 }
 
 static inline TSNode ts_node__direct_parent(TSNode self, uint32_t *index) {
@@ -324,11 +332,21 @@ TSNode ts_node_named_child(TSNode self, uint32_t child_index) {
 }
 
 uint32_t ts_node_child_count(TSNode self) {
-  return ts_node__tree(self)->visible_child_count;
+  const Tree *tree = ts_node__tree(self);
+  if (tree->child_count > 0) {
+    return tree->visible_child_count;
+  } else {
+    return 0;
+  }
 }
 
 uint32_t ts_node_named_child_count(TSNode self) {
-  return ts_node__tree(self)->named_child_count;
+  const Tree *tree = ts_node__tree(self);
+  if (tree->child_count > 0) {
+    return tree->named_child_count;
+  } else {
+    return 0;
+  }
 }
 
 TSNode ts_node_next_sibling(TSNode self) {

src/runtime/parser.c

@@ -752,8 +752,9 @@ static void parser__start(Parser *self, TSInput input, Tree *previous_tree) {
     LOG("new_parse");
   }
 
-  if (self->language->external_scanner.create)
-    self->language->external_scanner.create();
+  if (self->language->external_scanner.reset) {
+    self->language->external_scanner.reset(self->external_scanner_payload);
+  }
 
   ts_lexer_set_input(&self->lexer, input);
   ts_stack_clear(self->stack);

src/runtime/tree.h

@@ -22,10 +22,13 @@ typedef struct Tree {
   } context;
 
   uint32_t child_count;
-  uint32_t visible_child_count;
-  uint32_t named_child_count;
   union {
-    struct Tree **children;
+    struct {
+      uint32_t visible_child_count;
+      uint32_t named_child_count;
+      struct Tree **children;
+    };
+    TSExternalTokenState external_token_state;
     int32_t lookahead_char;
   };