From 5ee2d47bd0f7ef8c0137cad1e6c6f488537bf62f Mon Sep 17 00:00:00 2001
From: Zach Bjornson <zbbjornson@gmail.com>
Date: Sat, 23 Jan 2021 10:37:44 -0800
Subject: [PATCH] fix: summary.observe should validate labels correctly

Fixes #262
---
 CHANGELOG.md                           |  1 +
 lib/summary.js                         |  2 +-
 test/__snapshots__/summaryTest.js.snap |  2 ++
 test/summaryTest.js                    | 12 ++++++++++++
 4 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a8feed15..3b46805d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,7 @@ project adheres to [Semantic Versioning](http://semver.org/).
 
 - fix: push client attempting to write Promise
 - types: improve type checking of labels
+- fix: Summary#observe should throw when adding additional labels to labelset (fixes [#262](https://github.com/siimon/prom-client/issues/262))
 
 ### Added
 
diff --git a/lib/summary.js b/lib/summary.js
index e5afd1b8..788203d9 100644
--- a/lib/summary.js
+++ b/lib/summary.js
@@ -155,7 +155,7 @@ function observe(labels) {
 	return value => {
 		const labelValuePair = convertLabelsAndValues(labels, value);
 
-		validateLabel(this.labelNames, this.labels);
+		validateLabel(this.labelNames, labels);
 		if (!Number.isFinite(labelValuePair.value)) {
 			throw new TypeError(
 				`Value is not a valid number: ${util.format(labelValuePair.value)}`,
diff --git a/test/__snapshots__/summaryTest.js.snap b/test/__snapshots__/summaryTest.js.snap
index 998369b1..f9f18ce0 100644
--- a/test/__snapshots__/summaryTest.js.snap
+++ b/test/__snapshots__/summaryTest.js.snap
@@ -3,3 +3,5 @@
 exports[`summary global registry with param as object labels should throw error if label lengths does not match 1`] = `"Invalid number of arguments"`;
 
 exports[`summary global registry with param as object remove should throw error if label lengths does not match 1`] = `"Invalid number of arguments"`;
+
+exports[`summary global registry with param as object should validate labels when observing 1`] = `"Added label \\"baz\\" is not included in initial labelset: [ 'foo' ]"`;
diff --git a/test/summaryTest.js b/test/summaryTest.js
index bd119dfd..d9c11fb0 100644
--- a/test/summaryTest.js
+++ b/test/summaryTest.js
@@ -32,6 +32,18 @@ describe('summary', () => {
 				expect((await instance.get()).values[8].value).toEqual(1);
 			});
 
+			it('should validate labels when observing', async () => {
+				const summary = new Summary({
+					name: 'foobar',
+					help: 'Foo Bar',
+					labelNames: ['foo'],
+				});
+
+				expect(() => {
+					summary.observe({ foo: 'bar', baz: 'qaz' }, 10);
+				}).toThrowErrorMatchingSnapshot();
+			});
+
 			it('should correctly calculate percentiles when more values are added to the summary', async () => {
 				instance.observe(100);
 				instance.observe(100);