[chore] prometheusreceiver: Refactor and remove dead code

receiver/prometheusreceiver/internal/targetallocator/config.go

@@ -47,24 +47,18 @@ func (cfg *Config) Validate() error {
 var _ confmap.Unmarshaler = (*PromHTTPSDConfig)(nil)
 
 func (cfg *PromHTTPSDConfig) Unmarshal(componentParser *confmap.Conf) error {
-	cfgMap := componentParser.ToStringMap()
-	if len(cfgMap) == 0 {
-		return nil
-	}
-	cfgMap["url"] = "http://placeholder" // we have to set it as else marshaling will fail
-	return unmarshalYAML(cfgMap, (*promHTTP.SDConfig)(cfg))
+	return unmarshalConf(componentParser, func(m map[string]any) {
+		// we have to set it as else marshaling will fail
+		m["url"] = "http://placeholder"
+	}, (*promHTTP.SDConfig)(cfg))
 }
 
 type PromHTTPClientConfig commonconfig.HTTPClientConfig
 
 var _ confmap.Unmarshaler = (*PromHTTPClientConfig)(nil)
 
 func (cfg *PromHTTPClientConfig) Unmarshal(componentParser *confmap.Conf) error {
-	cfgMap := componentParser.ToStringMap()
-	if len(cfgMap) == 0 {
-		return nil
-	}
-	return unmarshalYAML(cfgMap, (*commonconfig.HTTPClientConfig)(cfg))
+	return unmarshalConf(componentParser, nil, (*commonconfig.HTTPClientConfig)(cfg))
 }
 
 func (cfg *PromHTTPClientConfig) Validate() error {
@@ -109,13 +103,21 @@ func checkTLSConfig(tlsConfig commonconfig.TLSConfig) error {
 	return nil
 }
 
-func unmarshalYAML(in map[string]any, out any) error {
-	yamlOut, err := yaml.MarshalWithOptions(
-		in,
-		yaml.CustomMarshaler[commonconfig.Secret](func(s commonconfig.Secret) ([]byte, error) {
-			return []byte(s), nil
-		}),
-	)
+// unmarshalConf unmarshals conf to out.
+// YAML is used as an intermediary format, because confmap.Conf.Unmarshal is incompatible with Prometheus types,
+// as the former uses mapstructure tags .
+// If cb is not nil, it's called to mutate the map representation of conf.
+func unmarshalConf(conf *confmap.Conf, cb func(map[string]any), out any) error {
+	in := conf.ToStringMap()
+	if len(in) == 0 {
+		return nil
+	}
+
+	if cb != nil {
+		cb(in)
+	}
+
+	yamlOut, err := yaml.Marshal(in)
 	if err != nil {
 		return fmt.Errorf("prometheus receiver: failed to marshal config to yaml: %w", err)
 	}

receiver/prometheusreceiver/internal/targetallocator/config_test.go

@@ -25,20 +25,39 @@ func TestComponentConfigStruct(t *testing.T) {
 }
 
 func TestLoadTargetAllocatorConfig(t *testing.T) {
-	cm, err := confmaptest.LoadConf(filepath.Join("testdata", "config.yaml"))
-	require.NoError(t, err)
-	cfg := &Config{}
+	t.Run("basic", func(t *testing.T) {
+		cm, err := confmaptest.LoadConf(filepath.Join("testdata", "config.yaml"))
+		require.NoError(t, err)
+		cfg := &Config{}
 
-	sub, err := cm.Sub("target_allocator")
-	require.NoError(t, err)
-	require.NoError(t, sub.Unmarshal(cfg))
-	require.NoError(t, xconfmap.Validate(cfg))
+		sub, err := cm.Sub("target_allocator")
+		require.NoError(t, err)
+		require.NoError(t, sub.Unmarshal(cfg))
+		require.NoError(t, xconfmap.Validate(cfg))
+
+		assert.Equal(t, "http://localhost:8080", cfg.Endpoint)
+		assert.Equal(t, 5*time.Second, cfg.Timeout)
+		assert.Equal(t, "client.crt", cfg.TLS.CertFile)
+		assert.Equal(t, 30*time.Second, cfg.Interval)
+		assert.Equal(t, "collector-1", cfg.CollectorID)
+	})
+
+	t.Run("special characters in password", func(t *testing.T) {
+		cm, err := confmaptest.LoadConf(filepath.Join("testdata", "config_with_special_chars.yaml"))
+		require.NoError(t, err)
 
-	assert.Equal(t, "http://localhost:8080", cfg.Endpoint)
-	assert.Equal(t, 5*time.Second, cfg.Timeout)
-	assert.Equal(t, "client.crt", cfg.TLS.CertFile)
-	assert.Equal(t, 30*time.Second, cfg.Interval)
-	assert.Equal(t, "collector-1", cfg.CollectorID)
+		var cfg Config
+		sub, err := cm.Sub("target_allocator")
+		require.NoError(t, err)
+		require.NoError(t, sub.Unmarshal(&cfg))
+
+		require.NotNil(t, cfg.HTTPSDConfig, "http_sd_config should be present")
+		require.NotNil(t, cfg.HTTPScrapeConfig, "http_scrape_config should be present")
+		require.NotNil(t, cfg.HTTPScrapeConfig.BasicAuth, "basic_auth should be present")
+		assert.Equal(t, "testuser", cfg.HTTPScrapeConfig.BasicAuth.Username)
+		assert.Equal(t, "%password-with-percent", string(cfg.HTTPScrapeConfig.BasicAuth.Password),
+			"password with special YAML characters should be preserved")
+	})
 }
 
 func TestPromHTTPClientConfigValidateAuthorization(t *testing.T) {
@@ -488,3 +507,50 @@ func TestConfigureSDHTTPClientConfigFromTA_Errors(t *testing.T) {
 		})
 	}
 }
+
+func TestUnmarshalConf(t *testing.T) {
+	t.Run("empty config", func(t *testing.T) {
+		var cfg promConfig.HTTPClientConfig
+		err := unmarshalConf(confmap.NewFromStringMap(map[string]any{}), nil, &cfg)
+		require.NoError(t, err)
+		assert.Zero(t, cfg)
+	})
+
+	t.Run("special YAML characters preserved", func(t *testing.T) {
+		var cfg promConfig.HTTPClientConfig
+		input := map[string]any{
+			"basic_auth": map[string]any{
+				"username": "user",
+				"password": "%password-with-percent",
+			},
+		}
+		err := unmarshalConf(confmap.NewFromStringMap(input), nil, &cfg)
+		require.NoError(t, err)
+		require.NotNil(t, cfg.BasicAuth)
+		assert.Equal(t, "%password-with-percent", string(cfg.BasicAuth.Password))
+	})
+
+	t.Run("callback mutates config", func(t *testing.T) {
+		var cfg promConfig.HTTPClientConfig
+		input := map[string]any{
+			"basic_auth": map[string]any{
+				"username": "original",
+			},
+		}
+		cb := func(m map[string]any) {
+			m["basic_auth"].(map[string]any)["username"] = "mutated"
+		}
+		require.NoError(t, unmarshalConf(confmap.NewFromStringMap(input), cb, &cfg))
+		require.NotNil(t, cfg.BasicAuth)
+		assert.Equal(t, "mutated", cfg.BasicAuth.Username)
+	})
+
+	t.Run("marshal error", func(t *testing.T) {
+		var cfg promConfig.HTTPClientConfig
+		input := map[string]any{
+			"invalid": make(chan int), // channels can't be marshaled to YAML
+		}
+		err := unmarshalConf(confmap.NewFromStringMap(input), nil, &cfg)
+		require.ErrorContains(t, err, "failed to marshal")
+	})
+}

receiver/prometheusreceiver/internal/targetallocator/testdata/config_with_special_chars.yaml

@@ -0,0 +1,10 @@
+target_allocator:
+  endpoint: http://localhost:8080
+  interval: 30s
+  collector_id: collector-1
+  http_sd_config:
+    refresh_interval: 60s
+  http_scrape_config:
+    basic_auth:
+      username: testuser
+      password: "%password-with-percent"