Add omitempty to JSON fields in alert, forecast, and observation services

internal/adapters/httpapi/server_test.go

@@ -232,3 +232,70 @@ func TestForecastReturnsUSUnits(t *testing.T) {
 		t.Fatalf("expected forecast timestamp passed to repo")
 	}
 }
+
+func TestNullFieldsAreOmittedFromJSON(t *testing.T) {
+	obsRepo := &fakeObservationRepo{
+		summary: ports.ObservationSummaryMetric{},
+		conditions: []ports.ObservationConditionMetric{
+			{
+				ObservedAt: time.Date(2026, 3, 17, 12, 0, 0, 0, time.UTC),
+			},
+		},
+	}
+	fcRepo := &fakeForecastRepo{
+		periods: []ports.ForecastPeriodMetric{
+			{
+				PeriodIndex:   1,
+				StartTime:     time.Date(2026, 3, 17, 12, 0, 0, 0, time.UTC),
+				EndTime:       time.Date(2026, 3, 17, 13, 0, 0, 0, time.UTC),
+				ConditionCode: 1,
+			},
+		},
+	}
+
+	server := NewServer(
+		observations.NewService(obsRepo, units.USConverter{}, constants.ObservationWindow),
+		forecasts.NewService(fcRepo, units.USConverter{}, constants.ForecastQueryLimit),
+		alerts.NewService(fakeAlertRepo{}),
+	).Handler()
+
+	wObs := httptest.NewRecorder()
+	server.ServeHTTP(wObs, httptest.NewRequest(http.MethodGet, "/observations/current", nil))
+	if wObs.Code != http.StatusOK {
+		t.Fatalf("expected observations 200, got %d", wObs.Code)
+	}
+
+	var obsPayload map[string]any
+	if err := json.Unmarshal(wObs.Body.Bytes(), &obsPayload); err != nil {
+		t.Fatalf("decode observations response: %v", err)
+	}
+	summary := obsPayload["summary"].(map[string]any)
+	if _, exists := summary["temperatureF"]; exists {
+		t.Fatalf("expected summary.temperatureF to be omitted when nil")
+	}
+
+	conditions := obsPayload["conditions"].([]any)
+	firstCond := conditions[0].(map[string]any)
+	if _, exists := firstCond["temperatureF"]; exists {
+		t.Fatalf("expected conditions[0].temperatureF to be omitted when nil")
+	}
+
+	wFc := httptest.NewRecorder()
+	server.ServeHTTP(wFc, httptest.NewRequest(http.MethodGet, "/forecast?timestamp=2026-03-17T12:30:00Z", nil))
+	if wFc.Code != http.StatusOK {
+		t.Fatalf("expected forecast 200, got %d", wFc.Code)
+	}
+
+	var fcPayload map[string]any
+	if err := json.Unmarshal(wFc.Body.Bytes(), &fcPayload); err != nil {
+		t.Fatalf("decode forecast response: %v", err)
+	}
+	periods := fcPayload["periods"].([]any)
+	firstPeriod := periods[0].(map[string]any)
+	if _, exists := firstPeriod["temperatureF"]; exists {
+		t.Fatalf("expected periods[0].temperatureF to be omitted when nil")
+	}
+	if _, exists := firstPeriod["windSpeedMph"]; exists {
+		t.Fatalf("expected periods[0].windSpeedMph to be omitted when nil")
+	}
+}