feat!: consolidated configuration change events into one event (#241)

## This PR

Consolidates configuration change events into a singular event (avoid
superfluous bulk emissions).
Existing `configuration_change` event listeners will need to update
their handling to consume the singular events.

### Related Issues
<!-- add here the GitHub issue that this PR resolves if applicable -->

Fixes #238 

- [x] [Update
go-sdk-contrib](open-feature/go-sdk-contrib#66)
- [ ] Update java-sdk-contrib

### Notes
<!-- any additional notes for this PR -->

### Follow-up Tasks
<!-- anything that is related to this PR but not done here should be
noted under this section -->
<!-- if there is a need for a new issue, please link it here -->

### How to test
<!-- if applicable, add testing instructions under this section -->

Signed-off-by: Skye Gill <gill.skye95@gmail.com>

pkg/eval/ievaluator.go

@@ -12,19 +12,13 @@ const (
 	NotificationUpdate StateChangeNotificationType = "update"
 )
 
-type StateChangeNotification struct {
-	Type    StateChangeNotificationType `json:"type"`
-	Source  string                      `json:"source"`
-	FlagKey string                      `json:"flagKey"`
-}
-
 /*
 IEvaluator implementations store the state of the flags,
 do parsing and validation of the flag state and evaluate flags in response to handlers.
 */
 type IEvaluator interface {
 	GetState() (string, error)
-	SetState(source string, state string) ([]StateChangeNotification, error)
+	SetState(source string, state string) (map[string]interface{}, error)
 
 	ResolveBooleanValue(
 		reqID string,
@@ -47,11 +41,3 @@ type IEvaluator interface {
 		flagKey string,
 		context *structpb.Struct) (value map[string]any, variant string, reasons string, err error)
 }
-
-func (s *StateChangeNotification) ToMap() map[string]interface{} {
-	return map[string]interface{}{
-		"type":    string(s.Type),
-		"source":  s.Source,
-		"flagKey": s.FlagKey,
-	}
-}

pkg/eval/json_evaluator.go

@@ -49,7 +49,7 @@ func (je *JSONEvaluator) GetState() (string, error) {
 	return string(data), nil
 }
 
-func (je *JSONEvaluator) SetState(source string, state string) ([]StateChangeNotification, error) {
+func (je *JSONEvaluator) SetState(source string, state string) (map[string]interface{}, error) {
 	schemaLoader := gojsonschema.NewStringLoader(schema.FlagdDefinitions)
 	flagStringLoader := gojsonschema.NewStringLoader(state)
 	result, err := gojsonschema.Validate(schemaLoader, flagStringLoader)

pkg/eval/json_evaluator_model.go

@@ -16,18 +16,17 @@ type Evaluators struct {
 	Evaluators map[string]json.RawMessage `json:"$evaluators"`
 }
 
-func (f Flags) Merge(logger *logger.Logger, source string, ff Flags) (Flags, []StateChangeNotification) {
-	notifications := []StateChangeNotification{}
+func (f Flags) Merge(logger *logger.Logger, source string, ff Flags) (Flags, map[string]interface{}) {
+	notifications := map[string]interface{}{}
 	result := Flags{Flags: make(map[string]Flag)}
 	for k, v := range f.Flags {
 		if v.Source == source {
 			if _, ok := ff.Flags[k]; !ok {
 				// flag has been deleted
-				notifications = append(notifications, StateChangeNotification{
-					Type:    NotificationDelete,
-					Source:  source,
-					FlagKey: k,
-				})
+				notifications[k] = map[string]interface{}{
+					"type":   string(NotificationDelete),
+					"source": source,
+				}
 				continue
 			}
 		}
@@ -37,11 +36,10 @@ func (f Flags) Merge(logger *logger.Logger, source string, ff Flags) (Flags, []S
 		v.Source = source
 		val, ok := result.Flags[k]
 		if !ok {
-			notifications = append(notifications, StateChangeNotification{
-				Type:    NotificationCreate,
-				Source:  source,
-				FlagKey: k,
-			})
+			notifications[k] = map[string]interface{}{
+				"type":   string(NotificationCreate),
+				"source": source,
+			}
 		} else if !reflect.DeepEqual(val, v) {
 			if val.Source != source {
 				logger.Warn(
@@ -53,11 +51,10 @@ func (f Flags) Merge(logger *logger.Logger, source string, ff Flags) (Flags, []S
 					),
 				)
 			}
-			notifications = append(notifications, StateChangeNotification{
-				Type:    NotificationUpdate,
-				Source:  source,
-				FlagKey: k,
-			})
+			notifications[k] = map[string]interface{}{
+				"type":   string(NotificationUpdate),
+				"source": source,
+			}
 		}
 		result.Flags[k] = v
 	}

pkg/eval/json_evaluator_test.go

@@ -739,35 +739,40 @@ func BenchmarkResolveObjectValue(b *testing.B) {
 func TestMergeFlags(t *testing.T) {
 	t.Parallel()
 	tests := []struct {
-		name      string
-		current   eval.Flags
-		new       eval.Flags
-		newSource string
-		want      eval.Flags
+		name       string
+		current    eval.Flags
+		new        eval.Flags
+		newSource  string
+		want       eval.Flags
+		wantNotifs map[string]interface{}
 	}{
 		{
-			name:    "both nil",
-			current: eval.Flags{Flags: nil},
-			new:     eval.Flags{Flags: nil},
-			want:    eval.Flags{Flags: map[string]eval.Flag{}},
+			name:       "both nil",
+			current:    eval.Flags{Flags: nil},
+			new:        eval.Flags{Flags: nil},
+			want:       eval.Flags{Flags: map[string]eval.Flag{}},
+			wantNotifs: map[string]interface{}{},
 		},
 		{
-			name:    "both empty flags",
-			current: eval.Flags{Flags: map[string]eval.Flag{}},
-			new:     eval.Flags{Flags: map[string]eval.Flag{}},
-			want:    eval.Flags{Flags: map[string]eval.Flag{}},
+			name:       "both empty flags",
+			current:    eval.Flags{Flags: map[string]eval.Flag{}},
+			new:        eval.Flags{Flags: map[string]eval.Flag{}},
+			want:       eval.Flags{Flags: map[string]eval.Flag{}},
+			wantNotifs: map[string]interface{}{},
 		},
 		{
-			name:    "empty current",
-			current: eval.Flags{Flags: nil},
-			new:     eval.Flags{Flags: map[string]eval.Flag{}},
-			want:    eval.Flags{Flags: map[string]eval.Flag{}},
+			name:       "empty current",
+			current:    eval.Flags{Flags: nil},
+			new:        eval.Flags{Flags: map[string]eval.Flag{}},
+			want:       eval.Flags{Flags: map[string]eval.Flag{}},
+			wantNotifs: map[string]interface{}{},
 		},
 		{
-			name:    "empty new",
-			current: eval.Flags{Flags: map[string]eval.Flag{}},
-			new:     eval.Flags{Flags: nil},
-			want:    eval.Flags{Flags: map[string]eval.Flag{}},
+			name:       "empty new",
+			current:    eval.Flags{Flags: map[string]eval.Flag{}},
+			new:        eval.Flags{Flags: nil},
+			want:       eval.Flags{Flags: map[string]eval.Flag{}},
+			wantNotifs: map[string]interface{}{},
 		},
 		{
 			name: "extra fields on each",
@@ -793,6 +798,9 @@ func TestMergeFlags(t *testing.T) {
 					Source:         "2",
 				},
 			}},
+			wantNotifs: map[string]interface{}{
+				"paka": map[string]interface{}{"type": "write", "source": "2"},
+			},
 		},
 		{
 			name: "override",
@@ -807,6 +815,10 @@ func TestMergeFlags(t *testing.T) {
 				"waka": {DefaultVariant: "on"},
 				"paka": {DefaultVariant: "on"},
 			}},
+			wantNotifs: map[string]interface{}{
+				"waka": map[string]interface{}{"type": "update", "source": ""},
+				"paka": map[string]interface{}{"type": "write", "source": ""},
+			},
 		},
 		{
 			name: "identical",
@@ -819,15 +831,17 @@ func TestMergeFlags(t *testing.T) {
 			want: eval.Flags{Flags: map[string]eval.Flag{
 				"hello": {DefaultVariant: "off"},
 			}},
+			wantNotifs: map[string]interface{}{},
 		},
 	}
 
 	for _, tt := range tests {
 		tt := tt
 		t.Run(tt.name, func(t *testing.T) {
 			t.Parallel()
-			got, _ := tt.current.Merge(logger.NewLogger(nil, false), tt.newSource, tt.new)
+			got, gotNotifs := tt.current.Merge(logger.NewLogger(nil, false), tt.newSource, tt.new)
 			require.Equal(t, tt.want, got)
+			require.Equal(t, tt.wantNotifs, gotNotifs)
 		})
 	}
 }

pkg/runtime/runtime.go

@@ -80,12 +80,12 @@ func (r *Runtime) updateState(ctx context.Context, syncr sync.ISync) error {
 	if err != nil {
 		return fmt.Errorf("set state: %w", err)
 	}
-	for _, n := range notifications {
-		r.Logger.Info(fmt.Sprintf("configuration change (%s) for flagKey %s (%s)", n.Type, n.FlagKey, n.Source))
-		r.Service.Notify(service.Notification{
-			Type: service.ConfigurationChange,
-			Data: n.ToMap(),
-		})
-	}
+
+	r.Service.Notify(service.Notification{
+		Type: service.ConfigurationChange,
+		Data: map[string]interface{}{
+			"flags": notifications,
+		},
+	})
 	return nil
 }