fix: mergeSchemaWithRows can be called with empty schema if result set is empty (#1455)

Author: alvarowolfx

src/bigquery.ts

@@ -580,7 +580,7 @@ export class BigQuery extends Service {
  * @returns Fields using their matching names from the table's schema.
  */
  static mergeSchemaWithRows_(
- schema: TableSchema | TableField,
+ schema: TableSchema | TableField | undefined,
  rows: TableRow[],
  options: {
  wrapIntegers: boolean | IntegerTypeCastOptions;
@@ -589,7 +589,7 @@ export class BigQuery extends Service {
  }
  ) {
  // deep copy schema fields to avoid mutation
- let schemaFields: TableField[] = extend(true, [], schema.fields);
+ let schemaFields: TableField[] = extend(true, [], schema?.fields);
  let selectedFields: string[] = extend(true, [], options.selectedFields);
  if (options.selectedFields && options.selectedFields!.length > 0) {
  const selectedFieldsArray = options.selectedFields!.map(c => {

system-test/bigquery.ts

@@ -896,6 +896,18 @@ describe('BigQuery', () => {
  });
  });
 
+ // Empty results sets will not fetch table schema
+ it('should get the rows from an empty table', async () => {
+ const emptyTableId = generateName('empty-table');
+ await dataset.createTable(emptyTableId, {
+ schema: [{name: 'id', type: 'STRING'}],
+ });
+ const emptyTable = dataset.table(emptyTableId);
+ const [rows] = await emptyTable.getRows();
+ assert(Array.isArray(rows));
+ assert.equal(rows.length, 0);
+ });
+
  it('should get the rows in a table via stream', done => {
  table
  .createReadStream()