fix(utf8): fix config logic for name validation

We should only overwrite the ScrapeConfig if it is empty.

Added tests

part of https://github.com/prometheus/prometheus/issues/13095

Signed-off-by: Owen Williams <owen.williams@grafana.com>

config/config.go

@@ -781,7 +781,9 @@ func (c *ScrapeConfig) Validate(globalConfig GlobalConfig) error {
 	default:
 		return fmt.Errorf("unknown name validation method specified, must be either 'legacy' or 'utf8', got %s", globalConfig.MetricNameValidationScheme)
 	}
-	c.MetricNameValidationScheme = globalConfig.MetricNameValidationScheme
+	if c.MetricNameValidationScheme == "" {
+		c.MetricNameValidationScheme = globalConfig.MetricNameValidationScheme
+	}
 
 	return nil
 }

config/config_test.go

@@ -16,6 +16,7 @@ package config
 import (
 	"crypto/tls"
 	"encoding/json"
+	"fmt"
 	"net/url"
 	"os"
 	"path/filepath"
@@ -2300,3 +2301,52 @@ func TestScrapeConfigDisableCompression(t *testing.T) {
 
 	require.False(t, got.ScrapeConfigs[0].EnableCompression)
 }
+
+func TestScrapeConfigNameValidationSettings(t *testing.T) {
+	model.NameValidationScheme = model.UTF8Validation
+	defer func() {
+		model.NameValidationScheme = model.LegacyValidation
+	}()
+
+	tests := []struct {
+		name         string
+		inputFile    string
+		expectScheme string
+	}{
+		{
+			name:         "blank config implies default",
+			inputFile:    "scrape_config_default_validation_mode",
+			expectScheme: "",
+		},
+		{
+			name:         "global setting implies local settings",
+			inputFile:    "scrape_config_global_validation_mode",
+			expectScheme: "utf8",
+		},
+		{
+			name:         "local setting",
+			inputFile:    "scrape_config_local_validation_mode",
+			expectScheme: "utf8",
+		},
+		{
+			name:         "local setting overrides global setting",
+			inputFile:    "scrape_config_local_global_validation_mode",
+			expectScheme: "legacy",
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			want, err := LoadFile(fmt.Sprintf("testdata/%s.yml", tc.inputFile), false, false, log.NewNopLogger())
+			require.NoError(t, err)
+
+			out, err := yaml.Marshal(want)
+
+			require.NoError(t, err)
+			got := &Config{}
+			require.NoError(t, yaml.UnmarshalStrict(out, got))
+
+			require.Equal(t, tc.expectScheme, got.ScrapeConfigs[0].MetricNameValidationScheme)
+		})
+	}
+}

config/testdata/scrape_config_default_validation_mode.yml

@@ -0,0 +1,2 @@
+scrape_configs:
+  - job_name: prometheus

config/testdata/scrape_config_global_validation_mode.yml

@@ -0,0 +1,4 @@
+global:
+  metric_name_validation_scheme: utf8
+scrape_configs:
+  - job_name: prometheus

config/testdata/scrape_config_local_global_validation_mode.yml

@@ -0,0 +1,5 @@
+global:
+  metric_name_validation_scheme: utf8
+scrape_configs:
+  - job_name: prometheus
+    metric_name_validation_scheme: legacy

config/testdata/scrape_config_local_validation_mode.yml

@@ -0,0 +1,3 @@
+scrape_configs:
+  - job_name: prometheus
+    metric_name_validation_scheme: utf8