feat: enhance error output on not valid name and label names

CHANGELOG.md

@@ -11,6 +11,11 @@ project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Changed
 
+- Show the invalid name in the output error in the abstract class `Metric`.
+- Show the invalid label names instead of a generic message in the abstract class `Metric`.
+- Return an array of the invalid label names in the function `validateLabelName` instead of a boolean. It was achieved changing the implementation from the array function `every` to `forEach` and negating the test regex in favor to return the rejected ones.
+- Change the conditional`if` to throw an error in case the label names are invalid using the array returned from the function `validateLabelName`.
+- Unit test added in the gauge test case. It could be performed in any other metric that inherits from the abstract class `Metric`.
 - Improve the memory usage of histograms when the `enableExemplars` option is disabled
 
 ### Added

lib/metric.js

@@ -34,10 +34,13 @@ class Metric {
 			throw new Error('Missing mandatory name parameter');
 		}
 		if (!validateMetricName(this.name)) {
-			throw new Error('Invalid metric name');
+			throw new Error(`Invalid metric name: ${this.name}`);
 		}
-		if (!validateLabelName(this.labelNames)) {
-			throw new Error('Invalid label name');
+		const invalidLabelNames = validateLabelName(this.labelNames);
+		if (invalidLabelNames.length > 0) {
+			throw new Error(
+				`At least one label name is invalid: ${invalidLabelNames.join(',')}`,
+			);
 		}
 
 		if (this.collect && typeof this.collect !== 'function') {

lib/validation.js

@@ -11,7 +11,7 @@ exports.validateMetricName = function (name) {
 };
 
 exports.validateLabelName = function (names = []) {
-	return names.every(name => labelRegexp.test(name));
+	return names.filter(name => !labelRegexp.test(name));
 };
 
 exports.validateLabel = function validateLabel(savedLabels, labels) {

test/gaugeTest.js

@@ -1,5 +1,6 @@
 'use strict';
 
+const { Metric } = require('../lib/metric');
 const Registry = require('../index').Registry;
 
 describe.each([
@@ -19,6 +20,44 @@ describe.each([
 			globalRegistry.clear();
 		});
 
+		describe('Metric instantiation', () => {
+			const defaultParams = { name: 'gauge_test', help: 'help' };
+
+			describe('happy path', () => {
+				it('should create a instance', async () => {
+					const instance = new Gauge(defaultParams);
+					const instanceValues = await instance.get();
+					expect(instance).toBeInstanceOf(Metric);
+					expect(instance).toBeInstanceOf(Gauge);
+					expect(instance.labelNames).toStrictEqual([]);
+					expect(instanceValues.name).toStrictEqual(defaultParams.name);
+					expect(instanceValues.help).toStrictEqual(defaultParams.help);
+				});
+			});
+
+			describe('un-happy path', () => {
+				const noValidName = 'no valid name';
+				it('should thrown an error due invalid metric name', () => {
+					expect(
+						() => new Gauge({ ...defaultParams, name: noValidName }),
+					).toThrow(new Error(`Invalid metric name: ${noValidName}`));
+				});
+
+				it('should thrown an error due some invalid label name', () => {
+					const noValidLabelNames = [noValidName, defaultParams.name];
+					expect(
+						() =>
+							new Gauge({
+								...defaultParams,
+								labelNames: noValidLabelNames,
+							}),
+					).toThrow(
+						new Error(`At least one label name is invalid: ${noValidName}`),
+					);
+				});
+			});
+		});
+
 		describe('with parameters as object', () => {
 			beforeEach(() => {
 				instance = new Gauge({ name: 'gauge_test', help: 'help' });