Wrap serdes parameters around the Settings interface

Thus allowing for:
- Shared parameters across `Secret`instances
- Mutable values.
- Memory footprint optimization

demo/app.go

@@ -48,8 +48,10 @@ func main() {
 	fmt.Println(string(marshalledAllSecrets))
 
 	// But we can set some fields open for JSON serialization
-	snowCrash.Characters[1].Name.CleartextJSON = true
-	snowCrash.Characters[1].Age.CleartextJSON = true
+	changedSettings := NewImmutableSettings(true)
+
+	snowCrash.Characters[1].Name.Settings = changedSettings
+	snowCrash.Characters[1].Age.Settings = changedSettings
 
 	marshalledSomeSecrets, _ := json.Marshal(snowCrash)
 	fmt.Println(string(marshalledSomeSecrets))

gosecretfields.go

@@ -20,9 +20,70 @@ type Secret[T any] struct {
 	// This is the value that replaces the secret value upon redaction.
 	redactedValue T
 
+	// Flag toggling redaction on and off for different kinds of serialization
+	// so far, only JSON serdes is configurable.
+	// By assigning references to the same value implementing the `Settings` interface,
+	// we are able to control a group of `Secret` instances serdes behaviour at the same time.
+	Settings Settings
+}
+
+// Common interface for per-secret instance settings.
+type Settings interface {
 	// Flag controling wether this secret should be JSON serialized with
 	// its secret or redacted value.
-	CleartextJSON bool
+	CleartextJSON() bool
+}
+
+// Implementation of the `Settings` interface that close down
+// changes after initialization.
+type ImmutableSettings struct {
+	enabledClearTextJSON bool
+}
+
+func NewImmutableSettings(enabledClearTextJSON bool) ImmutableSettings {
+	return ImmutableSettings{enabledClearTextJSON}
+}
+
+func (is ImmutableSettings) CleartextJSON() bool {
+	return is.enabledClearTextJSON
+}
+
+func (is *ImmutableSettings) CopyAsMutableSettings() MutableSettings {
+	return MutableSettings{
+		EnabledClearTextJSON: is.CleartextJSON(),
+	}
+}
+
+// Implementation of the `Settings` interface allowing for in place
+// mutation.
+type MutableSettings struct {
+	EnabledClearTextJSON bool
+}
+
+func (ms *MutableSettings) CleartextJSON() bool {
+	return ms.EnabledClearTextJSON
+}
+
+func (ms *MutableSettings) Copy() MutableSettings {
+	return MutableSettings{
+		EnabledClearTextJSON: ms.CleartextJSON(),
+	}
+}
+
+func (ms *MutableSettings) CopyAsImmutable() ImmutableSettings {
+	return ImmutableSettings{
+		enabledClearTextJSON: ms.CleartextJSON(),
+	}
+}
+
+// Shared static values
+
+var defaultSettings = ImmutableSettings{
+	enabledClearTextJSON: false,
+}
+
+func DefaultSettings() Settings {
+	return &defaultSettings
 }
 
 // Factories
@@ -39,7 +100,7 @@ func AsSecret[T any](value T, redactedValue ...T) Secret[T] {
 	return Secret[T]{
 		SecretValue:   value,
 		redactedValue: redacted,
-		CleartextJSON: false,
+		Settings:      DefaultSettings(),
 	}
 }
 
@@ -50,7 +111,7 @@ func (s Secret[T]) MarshalJSON() ([]byte, error) {
 	// Secret fields will result on the redactedValue or the actual secret value JSON representation
 	// but the container will never show in the JSON structure.
 	safeValue := s.redactedValue
-	if s.CleartextJSON {
+	if s.Settings.CleartextJSON() {
 		safeValue = s.SecretValue
 	}
 	return json.Marshal(safeValue)

gosecretfields_test.go

@@ -24,15 +24,15 @@ func TestAsSecret(t *testing.T) {
 				value:         "Hiro Protagonist",
 				redactedValue: []string{},
 			},
-			want: Secret[string]{SecretValue: "Hiro Protagonist", redactedValue: ""},
+			want: Secret[string]{SecretValue: "Hiro Protagonist", redactedValue: "", Settings: DefaultSettings()},
 		},
 		{
 			name: "With explicit redacted value",
 			args: args{
 				value:         "Hiro Protagonist",
 				redactedValue: []string{"REDACTED"},
 			},
-			want: Secret[string]{SecretValue: "Hiro Protagonist", redactedValue: "REDACTED"},
+			want: Secret[string]{SecretValue: "Hiro Protagonist", redactedValue: "REDACTED", Settings: DefaultSettings()},
 		},
 	}
 	for _, tt := range tests {
@@ -75,6 +75,15 @@ func containsSecrets(text string) bool {
 
 func TestMarshallingAndStringer(t *testing.T) {
 
+	commonSettings := &MutableSettings{
+		EnabledClearTextJSON: true,
+	}
+
+	sampleCharacterHiro.Age.Settings = commonSettings
+	sampleCharacterHiro.Name.Settings = commonSettings
+	sampleCharacterYT.Age.Settings = commonSettings
+	sampleCharacterYT.Name.Settings = commonSettings
+
 	hiroWithFriend := sampleCharacterHiro
 	hiroWithFriend.Friend = &sampleCharacterYT
 
@@ -107,13 +116,7 @@ func TestMarshallingAndStringer(t *testing.T) {
 				t.Errorf("Stringer interface implementation must prevent secrets from leaking:\n%s", asString)
 			}
 
-			testCase.value.Name.CleartextJSON = !testCase.redactJson
-			testCase.value.Age.CleartextJSON = !testCase.redactJson
-
-			if maybeFriend := testCase.value.Friend; maybeFriend != nil {
-				maybeFriend.Name.CleartextJSON = !testCase.redactJson
-				maybeFriend.Age.CleartextJSON = !testCase.redactJson
-			}
+			commonSettings.EnabledClearTextJSON = !testCase.redactJson
 
 			var unmarshalled character
 
@@ -130,12 +133,12 @@ func TestMarshallingAndStringer(t *testing.T) {
 				t.Errorf("Unmarshalling should not fail. Error: %s", unmarshallingError)
 			}
 
-			unmarshalled.Name.CleartextJSON = !testCase.redactJson
-			unmarshalled.Age.CleartextJSON = !testCase.redactJson
+			unmarshalled.Name.Settings = commonSettings
+			unmarshalled.Age.Settings = commonSettings
 
 			if maybeUnmarshalledFriend := unmarshalled.Friend; maybeUnmarshalledFriend != nil {
-				maybeUnmarshalledFriend.Name.CleartextJSON = !testCase.redactJson
-				maybeUnmarshalledFriend.Age.CleartextJSON = !testCase.redactJson
+				maybeUnmarshalledFriend.Name.Settings = commonSettings
+				maybeUnmarshalledFriend.Age.Settings = commonSettings
 			}
 
 			if !testCase.redactJson && !reflect.DeepEqual(unmarshalled, testCase.value) {