From 528b3fc60fc3e06d27c02a59451a3ec969cd4a02 Mon Sep 17 00:00:00 2001
From: Matt Hughes <mhughes@uw.co.uk>
Date: Thu, 20 Feb 2025 11:22:23 +0000
Subject: [PATCH] scraper: fix UTF-8 scraping header always sent with
 PrometheusText1.0.0

The `Accept` header should not include `escape=allow-utf-8` unless
explicitly requested.

Conveniently, there was already a test covering this header's value, it
just required updating so it also asserts that this value in the header
is not set in the cases we don't expect it to be set. I also converted
those tests into table tests to help make failures clearer.

Issue: https://github.com/prometheus/prometheus/issues/15857
Signed-off-by: Matt Hughes <mhughes@uw.co.uk>
---
 config/config.go      |  2 +-
 scrape/scrape_test.go | 49 +++++++++++++++++++++++++++++++++++--------
 2 files changed, 41 insertions(+), 10 deletions(-)

diff --git a/config/config.go b/config/config.go
index 73282ac429..465affe082 100644
--- a/config/config.go
+++ b/config/config.go
@@ -523,7 +523,7 @@ var (
 	ScrapeProtocolsHeaders = map[ScrapeProtocol]string{
 		PrometheusProto:      "application/vnd.google.protobuf;proto=io.prometheus.client.MetricFamily;encoding=delimited",
 		PrometheusText0_0_4:  "text/plain;version=0.0.4",
-		PrometheusText1_0_0:  "text/plain;version=1.0.0;escaping=allow-utf-8",
+		PrometheusText1_0_0:  "text/plain;version=1.0.0",
 		OpenMetricsText0_0_1: "application/openmetrics-text;version=0.0.1",
 		OpenMetricsText1_0_0: "application/openmetrics-text;version=1.0.0",
 	}
diff --git a/scrape/scrape_test.go b/scrape/scrape_test.go
index 26117ffd08..75fed524c4 100644
--- a/scrape/scrape_test.go
+++ b/scrape/scrape_test.go
@@ -2825,6 +2825,8 @@ func TestTargetScraperScrapeOK(t *testing.T) {
 			accept := r.Header.Get("Accept")
 			if allowUTF8 {
 				require.Containsf(t, accept, "escaping=allow-utf-8", "Expected Accept header to allow utf8, got %q", accept)
+			} else {
+				require.NotContainsf(t, accept, "escaping=allow-utf-8", "Expected Accept header to not allow utf8, got %q", accept)
 			}
 			if protobufParsing {
 				require.True(t, strings.HasPrefix(accept, "application/vnd.google.protobuf;"),
@@ -2860,7 +2862,7 @@ func TestTargetScraperScrapeOK(t *testing.T) {
 		panic(err)
 	}
 
-	runTest := func(acceptHeader string) {
+	runTest := func(t *testing.T, acceptHeader string) {
 		ts := &targetScraper{
 			Target: &Target{
 				labels: labels.FromStrings(
@@ -2887,14 +2889,43 @@ func TestTargetScraperScrapeOK(t *testing.T) {
 		require.Equal(t, "metric_a 1\nmetric_b 2\n", buf.String())
 	}
 
-	runTest(acceptHeader(config.DefaultScrapeProtocols, model.LegacyValidation))
-	protobufParsing = true
-	runTest(acceptHeader(config.DefaultProtoFirstScrapeProtocols, model.LegacyValidation))
-	protobufParsing = false
-	allowUTF8 = true
-	runTest(acceptHeader(config.DefaultScrapeProtocols, model.UTF8Validation))
-	protobufParsing = true
-	runTest(acceptHeader(config.DefaultProtoFirstScrapeProtocols, model.UTF8Validation))
+	for _, tc := range []struct {
+		scrapeProtocols []config.ScrapeProtocol
+		scheme          model.ValidationScheme
+		protobufParsing bool
+		allowUTF8       bool
+	}{
+		{
+			scrapeProtocols: config.DefaultScrapeProtocols,
+			scheme:          model.LegacyValidation,
+			protobufParsing: false,
+			allowUTF8:       false,
+		},
+		{
+			scrapeProtocols: config.DefaultProtoFirstScrapeProtocols,
+			scheme:          model.LegacyValidation,
+			protobufParsing: true,
+			allowUTF8:       false,
+		},
+		{
+			scrapeProtocols: config.DefaultScrapeProtocols,
+			scheme:          model.UTF8Validation,
+			protobufParsing: false,
+			allowUTF8:       true,
+		},
+		{
+			scrapeProtocols: config.DefaultProtoFirstScrapeProtocols,
+			scheme:          model.UTF8Validation,
+			protobufParsing: true,
+			allowUTF8:       true,
+		},
+	} {
+		t.Run(fmt.Sprintf("%+v", tc), func(t *testing.T) {
+			protobufParsing = tc.protobufParsing
+			allowUTF8 = tc.allowUTF8
+			runTest(t, acceptHeader(tc.scrapeProtocols, tc.scheme))
+		})
+	}
 }
 
 func TestTargetScrapeScrapeCancel(t *testing.T) {