Handle set! predicate function in queries

lib/binding_web/binding.js

@@ -719,6 +719,7 @@ class Language {
       stringValues[i] = UTF8ToString(valueAddress, nameLength);
     }
 
+    const properties = new Array(patternCount);
     const predicates = new Array(patternCount);
     for (let i = 0; i < patternCount; i++) {
       const predicatesAddress = C._ts_query_predicates_for_pattern(
@@ -729,6 +730,8 @@ class Language {
       const stepCount = getValue(TRANSFER_BUFFER, 'i32');
 
       predicates[i] = [];
+      properties[i] = null;
+
       const steps = [];
       let stepAddress = predicatesAddress;
       for (let j = 0; j < stepCount; j++) {
@@ -741,14 +744,28 @@ class Language {
         } else if (stepType === PREDICATE_STEP_TYPE_STRING) {
           steps.push({type: 'string', value: stringValues[stepValueId]});
         } else if (steps.length > 0) {
-          predicates[i].push(buildQueryPredicate(steps));
+          const predicate = buildQueryPredicate(steps);
+          if (typeof predicate === 'function') {
+            predicates[i].push(predicate);
+          } else {
+            if (!properties[i]) properties[i] = {};
+            properties[i][predicate.key] = predicate.value;
+          }
           steps.length = 0;
         }
       }
+
+      Object.freeze(properties[i]);
     }
 
     C._free(sourceAddress);
-    return new Query(INTERNAL, address, captureNames, predicates);
+    return new Query(
+      INTERNAL,
+      address,
+      captureNames,
+      predicates,
+      Object.freeze(properties)
+    );
   }
 
   static load(url) {
@@ -784,11 +801,12 @@ class Language {
 }
 
 class Query {
-  constructor(internal, address, captureNames, predicates) {
+  constructor(internal, address, captureNames, predicates, properties) {
     assertInternal(internal);
     this[0] = address;
     this.captureNames = captureNames;
     this.predicates = predicates;
+    this.patternProperties = properties;
   }
 
   delete() {
@@ -826,6 +844,9 @@ class Query {
       if (this.predicates[pattern].every(p => p(captures))) {
         result[i] = {pattern, captures};
       }
+
+      const properties = this.patternProperties[pattern];
+      if (properties) result[i].properties = properties;
     }
 
     C._free(startAddress);
@@ -851,6 +872,7 @@ class Query {
     const startAddress = getValue(TRANSFER_BUFFER + SIZE_OF_INT, 'i32');
     const result = [];
 
+    const captures = [];
     let address = startAddress;
     for (let i = 0; i < count; i++) {
       const pattern = getValue(address, 'i32');
@@ -860,11 +882,14 @@ class Query {
       const captureIndex = getValue(address, 'i32');
       address += SIZE_OF_INT;
 
-      const captures = new Array(captureCount);
+      captures.length = captureCount
       address = unmarshalCaptures(this, node.tree, address, captures);
 
       if (this.predicates[pattern].every(p => p(captures))) {
-        result.push(captures[captureIndex]);
+        const capture = captures[captureIndex];
+        const properties = this.patternProperties[pattern];
+        if (properties) capture.properties = properties;
+        result.push(capture);
       }
     }
 
@@ -927,6 +952,18 @@ function buildQueryPredicate(steps) {
         return false;
       }
 
+    case 'set!':
+      if (steps.length !== 3) throw new Error(
+        `Wrong number of arguments to \`set!\` predicate. Expected 2, got ${steps.length - 1}.`
+      );
+      if (steps[1].type !== 'string' || steps[2].type !== 'string') throw new Error(
+        `Arguments to \`set!\` predicate must be a strings.".`
+      );
+      return {
+        key: steps[1].value,
+        value: steps[2].value,
+      };
+
     default:
       throw new Error(`Unknown query predicate \`${steps[0].value}\``);
   }