Cut 1.20.5; update comments.

Signed-off-by: bwplotka <bwplotka@gmail.com>

# Conflicts:
#	CHANGELOG.md

CHANGELOG.md

@@ -1,5 +1,11 @@
 ## Unreleased
 
+## 1.20.5 / 2024-10-15
+
+* [BUGFIX] testutil: Reverted #1424; functions using compareMetricFamilies are (again) only failing if filtered metricNames are in the expected input.
+
+## 1.20.4 / 2024-09-07
+
 * [BUGFIX] histograms: Fix possible data race when appending exemplars vs metrics gather. #1623
 
 ## 1.20.3 / 2024-09-05
@@ -28,7 +34,7 @@
 * [FEATURE] promlint: Add duplicated metric lint rule. #1472
 * [BUGFIX] promlint: Relax metric type in name linter rule. #1455
 * [BUGFIX] promhttp: Make sure server instrumentation wrapping supports new and future extra responseWriter methods. #1480
-* [BUGFIX] testutil: Functions using compareMetricFamilies are now failing if filtered metricNames are not in the input. #1424
+* [BUGFIX] **breaking** testutil: Functions using compareMetricFamilies are now failing if filtered metricNames are not in the input. #1424 (reverted in 1.20.5)
 
 ## 1.19.0 / 2024-02-27
 

VERSION

@@ -1 +1 @@
-1.20.2
+1.20.5

prometheus/testutil/testutil.go

@@ -158,6 +158,9 @@ func GatherAndCount(g prometheus.Gatherer, metricNames ...string) (int, error) {
 // ScrapeAndCompare calls a remote exporter's endpoint which is expected to return some metrics in
 // plain text format. Then it compares it with the results that the `expected` would return.
 // If the `metricNames` is not empty it would filter the comparison only to the given metric names.
+//
+// NOTE: Be mindful of accidental discrepancies between expected and metricNames; metricNames filter
+// both expected and scraped metrics. See https://github.com/prometheus/client_golang/issues/1351.
 func ScrapeAndCompare(url string, expected io.Reader, metricNames ...string) error {
 	resp, err := http.Get(url)
 	if err != nil {
@@ -185,6 +188,9 @@ func ScrapeAndCompare(url string, expected io.Reader, metricNames ...string) err
 
 // CollectAndCompare collects the metrics identified by `metricNames` and compares them in the Prometheus text
 // exposition format to the data read from expected.
+//
+// NOTE: Be mindful of accidental discrepancies between expected and metricNames; metricNames filter
+// both expected and collected metrics. See https://github.com/prometheus/client_golang/issues/1351.
 func CollectAndCompare(c prometheus.Collector, expected io.Reader, metricNames ...string) error {
 	reg := prometheus.NewPedanticRegistry()
 	if err := reg.Register(c); err != nil {
@@ -197,6 +203,9 @@ func CollectAndCompare(c prometheus.Collector, expected io.Reader, metricNames .
 // it to an expected output read from the provided Reader in the Prometheus text
 // exposition format. If any metricNames are provided, only metrics with those
 // names are compared.
+//
+// NOTE: Be mindful of accidental discrepancies between expected and metricNames; metricNames filter
+// both expected and gathered metrics. See https://github.com/prometheus/client_golang/issues/1351.
 func GatherAndCompare(g prometheus.Gatherer, expected io.Reader, metricNames ...string) error {
 	return TransactionalGatherAndCompare(prometheus.ToTransactionalGatherer(g), expected, metricNames...)
 }
@@ -205,6 +214,9 @@ func GatherAndCompare(g prometheus.Gatherer, expected io.Reader, metricNames ...
 // it to an expected output read from the provided Reader in the Prometheus text
 // exposition format. If any metricNames are provided, only metrics with those
 // names are compared.
+//
+// NOTE: Be mindful of accidental discrepancies between expected and metricNames; metricNames filter
+// both expected and gathered metrics. See https://github.com/prometheus/client_golang/issues/1351.
 func TransactionalGatherAndCompare(g prometheus.TransactionalGatherer, expected io.Reader, metricNames ...string) error {
 	got, done, err := g.Gather()
 	defer done()