feat(api): attach request meta to error envelopes

Co-Authored-By: Virgil <virgil@lethean.io>

middleware_test.go

@@ -73,6 +73,17 @@ func (g autoResponseMetaTestGroup) RegisterRoutes(rg *gin.RouterGroup) {
 	})
 }
 
+type autoErrorResponseMetaTestGroup struct{}
+
+func (g autoErrorResponseMetaTestGroup) Name() string     { return "auto-error-response-meta" }
+func (g autoErrorResponseMetaTestGroup) BasePath() string { return "/v1" }
+func (g autoErrorResponseMetaTestGroup) RegisterRoutes(rg *gin.RouterGroup) {
+	rg.GET("/error", func(c *gin.Context) {
+		time.Sleep(2 * time.Millisecond)
+		c.JSON(http.StatusBadRequest, api.Fail("bad_request", "request failed"))
+	})
+}
+
 // ── Bearer auth ─────────────────────────────────────────────────────────
 
 func TestBearerAuth_Bad_MissingToken(t *testing.T) {
@@ -310,6 +321,42 @@ func TestResponseMeta_Good_AttachesMetaAutomatically(t *testing.T) {
 	}
 }
 
+func TestResponseMeta_Good_AttachesMetaToErrorResponses(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	e, _ := api.New(
+		api.WithRequestID(),
+		api.WithResponseMeta(),
+	)
+	e.Register(autoErrorResponseMetaTestGroup{})
+
+	h := e.Handler()
+	w := httptest.NewRecorder()
+	req, _ := http.NewRequest(http.MethodGet, "/v1/error", nil)
+	req.Header.Set("X-Request-ID", "client-id-auto-error-meta")
+	h.ServeHTTP(w, req)
+
+	if w.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400, got %d", w.Code)
+	}
+
+	var resp api.Response[string]
+	if err := json.Unmarshal(w.Body.Bytes(), &resp); err != nil {
+		t.Fatalf("unmarshal error: %v", err)
+	}
+	if resp.Meta == nil {
+		t.Fatal("expected Meta to be present")
+	}
+	if resp.Meta.RequestID != "client-id-auto-error-meta" {
+		t.Fatalf("expected request_id=%q, got %q", "client-id-auto-error-meta", resp.Meta.RequestID)
+	}
+	if resp.Meta.Duration == "" {
+		t.Fatal("expected duration to be populated")
+	}
+	if resp.Error == nil || resp.Error.Code != "bad_request" {
+		t.Fatalf("expected bad_request error, got %+v", resp.Error)
+	}
+}
+
 // ── CORS ────────────────────────────────────────────────────────────────
 
 func TestCORS_Good_PreflightAllOrigins(t *testing.T) {

response_meta.go

@@ -104,8 +104,8 @@ func (w *responseMetaRecorder) commit() {
 	_, _ = w.ResponseWriter.Write(w.body.Bytes())
 }
 
-// responseMetaMiddleware injects request metadata into successful JSON
-// envelope responses before they are written to the client.
+// responseMetaMiddleware injects request metadata into JSON envelope
+// responses before they are written to the client.
 func responseMetaMiddleware() gin.HandlerFunc {
 	return func(c *gin.Context) {
 		if _, ok := c.Get(requestStartContextKey); !ok {
@@ -156,7 +156,9 @@ func refreshResponseMetaBody(body []byte, meta *Meta) []byte {
 	}
 
 	if _, ok := obj["success"]; !ok {
-		return body
+		if _, ok := obj["error"]; !ok {
+			return body
+		}
 	}
 
 	current := map[string]any{}