Add a custom JSON marshaller for Alertmanager configurations

Author: alexander-akhmetov

definition/json.go

@@ -0,0 +1,120 @@
+package definition
+
+import (
+	"unsafe"
+
+	jsoniter "github.com/json-iterator/go"
+	"github.com/modern-go/reflect2"
+	amcfg "github.com/prometheus/alertmanager/config"
+	commoncfg "github.com/prometheus/common/config"
+)
+
+// secretEncoder encodes Secret to plain text JSON,
+// avoding the default masking behavior of the structure.
+type secretEncoder struct {
+	isPtr bool
+}
+
+func (encoder *secretEncoder) Encode(ptr unsafe.Pointer, stream *jsoniter.Stream) {
+	if encoder.isPtr {
+		p := *(**string)(ptr)
+		if p == nil {
+			stream.WriteNil()
+			return
+		}
+		stream.WriteString(*p)
+	} else {
+		v := *(*string)(ptr)
+		stream.WriteString(v)
+	}
+}
+
+func (encoder *secretEncoder) IsEmpty(ptr unsafe.Pointer) bool {
+	if encoder.isPtr {
+		p := *(**string)(ptr)
+		if p == nil {
+			return true
+		}
+		return len(*p) == 0
+	}
+
+	return len(*(*string)(ptr)) == 0
+}
+
+// secretURLEncoder encodes SecretURL to plain text JSON,
+// avoding the default masking behavior of the structure.
+type secretURLEncoder struct {
+	isPtr bool
+}
+
+func (encoder *secretURLEncoder) Encode(ptr unsafe.Pointer, stream *jsoniter.Stream) {
+	if encoder.isPtr {
+		p := *(**amcfg.SecretURL)(ptr)
+		if p == nil {
+			stream.WriteNil()
+			return
+		}
+		encoder.encodeSecretURL(*p, stream)
+	} else {
+		v := *(*amcfg.SecretURL)(ptr)
+		encoder.encodeSecretURL(v, stream)
+	}
+}
+
+func (encoder *secretURLEncoder) IsEmpty(ptr unsafe.Pointer) bool {
+	if encoder.isPtr {
+		p := *(**amcfg.SecretURL)(ptr)
+		if p == nil {
+			return true
+		}
+		return encoder.isSecretURLEmpty(*p)
+	}
+
+	v := *(*amcfg.SecretURL)(ptr)
+	return encoder.isSecretURLEmpty(v)
+}
+
+func (encoder *secretURLEncoder) encodeSecretURL(v amcfg.SecretURL, stream *jsoniter.Stream) {
+	// SecretURL is a type alias for URL, so we can cast it to URL to access the URL field
+	url := amcfg.URL(v)
+	if url.URL != nil {
+		stream.WriteString(url.String())
+	} else {
+		stream.WriteNil()
+	}
+}
+
+func (encoder *secretURLEncoder) isSecretURLEmpty(v amcfg.SecretURL) bool {
+	url := amcfg.URL(v)
+	return url.URL == nil || url.String() == ""
+}
+
+func newPlainAPI() jsoniter.API {
+	api := jsoniter.ConfigCompatibleWithStandardLibrary
+
+	extension := jsoniter.EncoderExtension{
+		reflect2.TypeOfPtr((*amcfg.Secret)(nil)).Elem():     &secretEncoder{isPtr: false},
+		reflect2.TypeOfPtr((*amcfg.Secret)(nil)):            &secretEncoder{isPtr: true},
+		reflect2.TypeOfPtr((*commoncfg.Secret)(nil)).Elem(): &secretEncoder{isPtr: false},
+		reflect2.TypeOfPtr((*commoncfg.Secret)(nil)):        &secretEncoder{isPtr: true},
+		reflect2.TypeOfPtr((*amcfg.SecretURL)(nil)).Elem():  &secretURLEncoder{isPtr: false},
+		reflect2.TypeOfPtr((*amcfg.SecretURL)(nil)):         &secretURLEncoder{isPtr: true},
+	}
+
+	api.RegisterExtension(extension)
+
+	return api
+}
+
+var (
+	plainJSON = newPlainAPI()
+)
+
+// MarshalJSONWithSecrets marshals the given value to JSON with secrets in plain text.
+//
+// alertmanager's and prometeus' Secret and SecretURL types mask their values
+// when marshaled with the standard JSON or YAML marshallers. This function
+// preserves the values of these types by using a custom JSON encoder.
+func MarshalJSONWithSecrets(v any) ([]byte, error) {
+	return plainJSON.Marshal(v)
+}