Implement Wasm binding for Tree.getChangedRanges()

lib/binding_web/binding.c

@@ -74,6 +74,20 @@ static TSPoint unmarshal_point(const void **address) {
   return point;
 }
 
+static void marshal_range(TSRange *range) {
+  range->start_byte = byte_to_code_unit(range->start_byte);
+  range->end_byte = byte_to_code_unit(range->end_byte);
+  range->start_point.column = byte_to_code_unit(range->start_point.column);
+  range->end_point.column = byte_to_code_unit(range->end_point.column);
+}
+
+static void unmarshal_range(TSRange *range) {
+  range->start_byte = code_unit_to_byte(range->start_byte);
+  range->end_byte = code_unit_to_byte(range->end_byte);
+  range->start_point.column = code_unit_to_byte(range->start_point.column);
+  range->end_point.column = code_unit_to_byte(range->end_point.column);
+}
+
 static TSInputEdit unmarshal_edit() {
   TSInputEdit edit;
   const void **address = TRANSFER_BUFFER;
@@ -151,11 +165,7 @@ TSTree *ts_parser_parse_wasm(
   };
   if (range_count) {
     for (unsigned i = 0; i < range_count; i++) {
-      TSRange *range = &ranges[i];
-      range->start_byte = code_unit_to_byte(range->start_byte);
-      range->end_byte = code_unit_to_byte(range->end_byte);
-      range->start_point.column = code_unit_to_byte(range->start_point.column);
-      range->end_point.column = code_unit_to_byte(range->end_point.column);
+      unmarshal_range(&ranges[i]);
     }
     ts_parser_set_included_ranges(self, ranges, range_count);
     free(ranges);
@@ -178,6 +188,16 @@ void ts_tree_edit_wasm(TSTree *tree) {
   ts_tree_edit(tree, &edit);
 }
 
+void ts_tree_get_changed_ranges_wasm(TSTree *tree, TSTree *other) {
+  unsigned range_count;
+  TSRange *ranges = ts_tree_get_changed_ranges(tree, other, &range_count);
+  for (unsigned i = 0; i < range_count; i++) {
+    marshal_range(&ranges[i]);
+  }
+  TRANSFER_BUFFER[0] = (const void *)range_count;
+  TRANSFER_BUFFER[1] = (const void *)ranges;
+}
+
 /************************/
 /* Section - TreeCursor */
 /************************/

lib/binding_web/binding.js

@@ -175,6 +175,26 @@ class Tree {
   walk() {
     return this.rootNode.walk();
   }
+
+  getChangedRanges(other) {
+    if (other.constructor !== Tree) {
+      throw new TypeError('Argument must be a Tree');
+    }
+
+    C._ts_tree_get_changed_ranges_wasm(this[0], other[0]);
+    const count = getValue(TRANSFER_BUFFER, 'i32');
+    const buffer = getValue(TRANSFER_BUFFER + SIZE_OF_INT, 'i32');
+    const result = new Array(count);
+    if (count > 0) {
+      let address = buffer;
+      for (let i = 0; i < count; i++) {
+        result[i] = unmarshalRange(address);
+        address += SIZE_OF_RANGE;
+      }
+      C._free(buffer);
+    }
+    return result;
+  }
 }
 
 class Node {

lib/binding_web/exports.json

@@ -81,5 +81,6 @@
   "_ts_tree_cursor_start_position_wasm",
   "_ts_tree_delete",
   "_ts_tree_edit_wasm",
+  "_ts_tree_get_changed_ranges_wasm",
   "_ts_tree_root_node_wasm"
 ]

lib/binding_web/test/tree-test.js

@@ -81,6 +81,54 @@ describe("Tree", () => {
     });
   });
 
+  describe(".getChangedRanges(previous)", () => {
+    it("reports the ranges of text whose syntactic meaning has changed", () => {
+      let sourceCode = "abcdefg + hij";
+      tree = parser.parse(sourceCode);
+
+      assert.equal(
+        tree.rootNode.toString(),
+        "(program (expression_statement (binary_expression (identifier) (identifier))))"
+      );
+
+      sourceCode = "abc + defg + hij";
+      tree.edit({
+        startIndex: 2,
+        oldEndIndex: 2,
+        newEndIndex: 5,
+        startPosition: { row: 0, column: 2 },
+        oldEndPosition: { row: 0, column: 2 },
+        newEndPosition: { row: 0, column: 5 }
+      });
+
+      const tree2 = parser.parse(sourceCode, tree);
+      assert.equal(
+        tree2.rootNode.toString(),
+        "(program (expression_statement (binary_expression (binary_expression (identifier) (identifier)) (identifier))))"
+      );
+
+      const ranges = tree.getChangedRanges(tree2);
+      assert.deepEqual(ranges, [
+        {
+          startIndex: 0,
+          endIndex: "abc + defg".length,
+          startPosition: { row: 0, column: 0 },
+          endPosition: { row: 0, column: "abc + defg".length }
+        }
+      ]);
+
+      tree2.delete();
+    });
+
+    it('throws an exception if the argument is not a tree', () => {
+      tree = parser.parse("abcdefg + hij");
+
+      assert.throws(() => {
+        tree.getChangedRanges({});
+      }, /Argument must be a Tree/);
+    })
+  });
+
   describe(".walk()", () => {
     let cursor