web: Implement TreeCursor.nodeText

Refs #466

lib/binding_web/binding.js

@@ -229,23 +229,7 @@ class Node {
   }
 
   get text() {
-    let {startIndex, endIndex} = this;
+    return getText(this.tree, this.startIndex, this.endIndex);
-    const length = endIndex - startIndex;
-    let result = this.tree.textCallback(startIndex, null, endIndex);
-    startIndex += result.length;
-    while (startIndex < endIndex) {
-      const string = this.tree.textCallback(startIndex, null, endIndex);
-      if (string && string.length > 0) {
-        startIndex += string.length;
-        result += string;
-      } else {
-        break;
-      }
-    }
-    if (startIndex > endIndex) {
-      result = result.slice(0, length);
-    }
-    return result;
   }
 
   isNamed() {
@@ -553,6 +537,13 @@ class TreeCursor {
     return C._ts_tree_cursor_current_node_is_missing_wasm(this.tree[0]) === 1;
   }
 
+  get nodeText() {
+    marshalTreeCursor(this);
+    const startIndex = C._ts_tree_cursor_start_index_wasm(this.tree[0]);
+    const endIndex = C._ts_tree_cursor_end_index_wasm(this.tree[0]);
+    return getText(this.tree, startIndex, endIndex);
+  }
+
   get startPosition() {
     marshalTreeCursor(this);
     C._ts_tree_cursor_start_position_wasm(this.tree[0]);
@@ -994,6 +985,25 @@ class Query {
   }
 }
 
+function getText(tree, startIndex, endIndex) {
+  const length = endIndex - startIndex;
+  let result = tree.textCallback(startIndex, null, endIndex);
+  startIndex += result.length;
+  while (startIndex < endIndex) {
+    const string = tree.textCallback(startIndex, null, endIndex);
+    if (string && string.length > 0) {
+      startIndex += string.length;
+      result += string;
+    } else {
+      break;
+    }
+  }
+  if (startIndex > endIndex) {
+    result = result.slice(0, length);
+  }
+  return result;
+}
+
 function unmarshalCaptures(query, tree, address, result) {
   for (let i = 0, n = result.length; i < n; i++) {
     const captureIndex = getValue(address, 'i32');

lib/binding_web/test/tree-test.js

@@ -180,6 +180,7 @@ describe("Tree", () => {
       });
 
       assert(cursor.gotoFirstChild());
+      assert.equal(cursor.nodeText, 'a');
       assertCursorState(cursor, {
         nodeType: 'identifier',
         nodeIsNamed: true,
@@ -191,6 +192,7 @@ describe("Tree", () => {
 
       assert(!cursor.gotoFirstChild())
       assert(cursor.gotoNextSibling());
+      assert.equal(cursor.nodeText, '*');
       assertCursorState(cursor, {
         nodeType: '*',
         nodeIsNamed: false,
@@ -201,6 +203,7 @@ describe("Tree", () => {
       });
 
       assert(cursor.gotoNextSibling());
+      assert.equal(cursor.nodeText, 'b');
       assertCursorState(cursor, {
         nodeType: 'identifier',
         nodeIsNamed: true,