Avoid including undefined in return value of Query.matches

Fixes #932

lib/binding_web/binding.js

@@ -967,12 +967,13 @@ class Query {
       endPosition.column
     );
 
-    const count = getValue(TRANSFER_BUFFER, 'i32');
+    const rawCount = getValue(TRANSFER_BUFFER, 'i32');
     const startAddress = getValue(TRANSFER_BUFFER + SIZE_OF_INT, 'i32');
-    const result = new Array(count);
+    const result = new Array(rawCount);
 
+    let filteredCount = 0;
     let address = startAddress;
-    for (let i = 0; i < count; i++) {
+    for (let i = 0; i < rawCount; i++) {
       const pattern = getValue(address, 'i32');
       address += SIZE_OF_INT;
       const captureCount = getValue(address, 'i32');
@@ -981,7 +982,7 @@ class Query {
       const captures = new Array(captureCount);
       address = unmarshalCaptures(this, node.tree, address, captures);
       if (this.textPredicates[pattern].every(p => p(captures))) {
-        result[i] = {pattern, captures};
+        result[filteredCount++] = {pattern, captures};
         const setProperties = this.setProperties[pattern];
         if (setProperties) result[i].setProperties = setProperties;
         const assertedProperties = this.assertedProperties[pattern];
@@ -990,6 +991,7 @@ class Query {
         if (refutedProperties) result[i].refutedProperties = refutedProperties;
       }
     }
+    result.length = filteredCount;
 
     C._free(startAddress);
     return result;

lib/binding_web/test/query-test.js

@@ -81,6 +81,32 @@ describe("Query", () => {
         { pattern: 0, captures: [{ name: "element", text: "g" }] },
       ]);
     });
+
+    it("handles predicates that compare the text of capture to literal strings", () => {
+      tree = parser.parse(`
+        giraffe(1, 2, []);
+        helment([false]);
+        goat(false);
+        gross(3, []);
+        hiccup([]);
+        gaff(5);
+      `);
+
+      // Find all calls to functions beginning with 'g', where one argument
+      // is an array literal.
+      query = JavaScript.query(`
+        (call_expression
+          function: (identifier) @name
+          arguments: (arguments (array))
+          (#match? @name "^g"))
+      `);
+
+      const matches = query.matches(tree.rootNode);
+      assert.deepEqual(formatMatches(matches), [
+        { pattern: 0, captures: [{name: "name", text: "giraffe" }] },
+        { pattern: 0, captures: [{name: "name", text: "gross" }] },
+      ]);
+    });
   });
 
   describe(".captures", () => {