@@ -34,7 +34,9 @@ import { isValidStringsOrObjects } from '../../../util/report-validation';
 export function isValidMetrics( metrics ) {
 	return isValidStringsOrObjects( metrics, ( metric ) => {
 		const validExpression = metric.hasOwnProperty( 'expression' ) && typeof metric.expression === 'string';
-		const validAlias = metric.hasOwnProperty( 'alias' ) && typeof metric.alias === 'string';
+
+		// 'alias' is optional; if provided, it must be a string.
+		const validAlias = ! metric.hasOwnProperty( 'alias' ) || typeof metric.alias === 'string';
 		return validExpression && validAlias;
 	} );
 }
/**
 * Reporting API validation utilities.
 *
 * Site Kit by Google, Copyright 2020 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * Internal dependencies
 */
import { isValidStringsOrObjects } from '../../../util/report-validation';

/**
 * Verifies that provided metrics match allowed values. Metrics can be a string,
 * an array of string, an array of objects or mix of strings and objects. Objects
 * must have "expression" and "alias" properties in order to be considered as valid.
 *
 * @since 1.13.0
 *
 * @param {string|string[]|Object|Object[]} metrics The metrics to check.
 * @return {boolean} TRUE if metrics are valid, otherwise FALSE.
 */
export function isValidMetrics( metrics ) {
	return isValidStringsOrObjects( metrics, ( metric ) => {
		const validExpression = metric.hasOwnProperty( 'expression' ) && typeof metric.expression === 'string';
		const validAlias = metric.hasOwnProperty( 'alias' ) && typeof metric.alias === 'string';
		return validExpression && validAlias;
	} );
}

/**
 * Verifies provided dimensions to make sure it matches allowed values. It can be a string,
 * array of strings, an object with "name" field, array of such objects or an array of strings
 * and objects.
 *
 * @since 1.13.0
 *
 * @param {string|string[]|Object|Object[]} dimensions The dimensions to check.
 * @return {boolean} TRUE if dimensions are valid, otherwise FALSE.
 */
export function isValidDimensions( dimensions ) {
	return isValidStringsOrObjects( dimensions, ( dimension ) => {
		return dimension.hasOwnProperty( 'name' ) && typeof dimension.name === 'string';
	} );
}

  although the doc block should be updated to reflect this as it currently contradicts this: > Objects must have "expression" and "alias" properties in order to be considered as valid.