GH-40407: [JS] Fix string coercion in MapRowProxyHandler.ownKeys (#40408

)

js/src/row/map.ts

@@ -24,20 +24,28 @@ import { instance as setVisitor } from '../visitor/set.js';
 
 /** @ignore */ export const kKeys = Symbol.for('keys');
 /** @ignore */ export const kVals = Symbol.for('vals');
+/** @ignore */ export const kKeysAsStrings = Symbol.for('kKeysAsStrings');
+/** @ignore */ export const _kKeysAsStrings = Symbol.for('_kKeysAsStrings');
 
 export class MapRow<K extends DataType = any, V extends DataType = any> {
 
  [key: string]: V['TValue'];
 
  declare private [kKeys]: Vector<K>;
  declare private [kVals]: Data<V>;
+ declare private [_kKeysAsStrings]: string[];
 
  constructor(slice: Data<Struct<{ key: K; value: V }>>) {
  this[kKeys] = new Vector([slice.children[0]]).memoize() as Vector<K>;
  this[kVals] = slice.children[1] as Data<V>;
  return new Proxy(this, new MapRowProxyHandler<K, V>());
  }
 
+ /** @ignore */
+ get [kKeysAsStrings]() {
+ return this[_kKeysAsStrings] || (this[_kKeysAsStrings] = Array.from(this[kKeys].toArray(), String));
+ }
+
  [Symbol.iterator]() {
  return new MapRowIterator(this[kKeys], this[kVals]);
  }
@@ -107,13 +115,13 @@ class MapRowProxyHandler<K extends DataType = any, V extends DataType = any> imp
  deleteProperty() { return false; }
  preventExtensions() { return true; }
  ownKeys(row: MapRow<K, V>) {
- return row[kKeys].toArray().map(String);
+ return row[kKeysAsStrings];
  }
  has(row: MapRow<K, V>, key: string | symbol) {
- return row[kKeys].includes(key);
+ return row[kKeysAsStrings].includes(key as string);
  }
  getOwnPropertyDescriptor(row: MapRow<K, V>, key: string | symbol) {
- const idx = row[kKeys].indexOf(key);
+ const idx = row[kKeysAsStrings].indexOf(key as string);
  if (idx !== -1) {
  return { writable: true, enumerable: true, configurable: true };
  }
@@ -124,7 +132,7 @@ class MapRowProxyHandler<K extends DataType = any, V extends DataType = any> imp
  if (Reflect.has(row, key)) {
  return (row as any)[key];
  }
- const idx = row[kKeys].indexOf(key);
+ const idx = row[kKeysAsStrings].indexOf(key as string);
  if (idx !== -1) {
  const val = getVisitor.visit(Reflect.get(row, kVals), idx);
  // Cache key/val lookups
@@ -133,7 +141,7 @@ class MapRowProxyHandler<K extends DataType = any, V extends DataType = any> imp
  }
  }
  set(row: MapRow<K, V>, key: string | symbol, val: V) {
- const idx = row[kKeys].indexOf(key);
+ const idx = row[kKeysAsStrings].indexOf(key as string);
  if (idx !== -1) {
  setVisitor.visit(Reflect.get(row, kVals), idx, val);
  // Cache key/val lookups
@@ -149,4 +157,5 @@ Object.defineProperties(MapRow.prototype, {
  [Symbol.toStringTag]: { enumerable: false, configurable: false, value: 'Row' },
  [kKeys]: { writable: true, enumerable: false, configurable: false, value: null },
  [kVals]: { writable: true, enumerable: false, configurable: false, value: null },
+ [_kKeysAsStrings]: { writable: true, enumerable: false, configurable: false, value: null },
 });