From 18ac5c0cc57a32b63ffe5ed354395a1a2607bb73 Mon Sep 17 00:00:00 2001
From: Viktar Tairau <tv@onl.by>
Date: Tue, 5 May 2026 22:05:08 +0300
Subject: [PATCH] Return defaults for non 2** statuses responses

---
 handler.go      |  2 +-
 handler_test.go | 95 +++++++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 89 insertions(+), 8 deletions(-)

diff --git a/handler.go b/handler.go
index 152b791..27b4353 100644
--- a/handler.go
+++ b/handler.go
@@ -30,7 +30,7 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	resp := rec.Result()
 
 	if !IsSuccess(resp) || !IsJSON(resp) {
-		h.write(w, resp)
+		h.write(w, NewJsonResponse(http.StatusOK, resp.Header, route.Default))
 		return
 	}
 
diff --git a/handler_test.go b/handler_test.go
index f65f570..49887c1 100644
--- a/handler_test.go
+++ b/handler_test.go
@@ -57,10 +57,13 @@ func TestHandler_RouteNotMatched_PassesThrough(t *testing.T) {
 	assert.Equal(t, "ok", rr.Body.String())
 }
 
-func TestHandler_Not2xx_PassesThrough(t *testing.T) {
+func TestHandler_Not2xx_JSON_ReturnsDefaults(t *testing.T) {
 	cfg := &Config{
 		Routes: []Route{
-			{Path: "/products/{product}/positions"},
+			{
+				Path:    "/products/{product}/positions",
+				Default: map[string]interface{}{"positions": []interface{}{}},
+			},
 		},
 	}
 
@@ -69,14 +72,90 @@ func TestHandler_Not2xx_PassesThrough(t *testing.T) {
 
 	rr := doRequest(t, h, "GET", "/products/iphonex64s/positions")
 
-	assert.Equal(t, http.StatusInternalServerError, rr.Code)
-	assert.Equal(t, `{"error":"boom"}`, rr.Body.String())
+	assert.Equal(t, http.StatusOK, rr.Code)
+
+	out := decodeJSON(t, rr.Body.Bytes())
+	assert.Equal(t, []interface{}{}, out["positions"])
+	_, hasError := out["error"]
+	assert.False(t, hasError)
 }
 
-func TestHandler_NotJSON_PassesThrough(t *testing.T) {
+func TestHandler_401_JSON_ReturnsDefaults(t *testing.T) {
 	cfg := &Config{
 		Routes: []Route{
-			{Path: "/products/{product}/positions"},
+			{
+				Path:    "/products/{product}/positions",
+				Default: map[string]interface{}{"positions": []interface{}{}, "shops": nil},
+			},
+		},
+	}
+
+	next := newNext(401, "application/json", `{"error":"unauthorized"}`)
+	h := NewHandler(cfg, next, noopLogger{})
+
+	rr := doRequest(t, h, "GET", "/products/iphonex64s/positions")
+
+	assert.Equal(t, http.StatusOK, rr.Code)
+
+	out := decodeJSON(t, rr.Body.Bytes())
+	_, ok := out["positions"]
+	assert.True(t, ok)
+	_, ok = out["shops"]
+	assert.True(t, ok)
+	_, hasError := out["error"]
+	assert.False(t, hasError)
+}
+
+func TestHandler_403_JSON_ReturnsDefaults(t *testing.T) {
+	cfg := &Config{
+		Routes: []Route{
+			{
+				Path:    "/products/{product}/positions",
+				Default: map[string]interface{}{"positions": []interface{}{}, "extra": "default_val"},
+			},
+		},
+	}
+
+	next := newNext(403, "application/json", `{"error":"forbidden","positions":[1,2]}`)
+	h := NewHandler(cfg, next, noopLogger{})
+
+	rr := doRequest(t, h, "GET", "/products/iphonex64s/positions")
+
+	assert.Equal(t, http.StatusOK, rr.Code)
+
+	out := decodeJSON(t, rr.Body.Bytes())
+	assert.Equal(t, []interface{}{}, out["positions"])
+	assert.Equal(t, "default_val", out["extra"])
+}
+
+func TestHandler_Not2xx_NotJSON_ReturnsDefaults(t *testing.T) {
+	cfg := &Config{
+		Routes: []Route{
+			{
+				Path:    "/products/{product}/positions",
+				Default: map[string]interface{}{"positions": []interface{}{}},
+			},
+		},
+	}
+
+	next := newNext(500, "text/plain", "internal error")
+	h := NewHandler(cfg, next, noopLogger{})
+
+	rr := doRequest(t, h, "GET", "/products/iphonex64s/positions")
+
+	assert.Equal(t, http.StatusOK, rr.Code)
+
+	out := decodeJSON(t, rr.Body.Bytes())
+	assert.Equal(t, []interface{}{}, out["positions"])
+}
+
+func TestHandler_NotJSON_ReturnsDefaults(t *testing.T) {
+	cfg := &Config{
+		Routes: []Route{
+			{
+				Path:    "/products/{product}/positions",
+				Default: map[string]interface{}{"positions": []interface{}{}},
+			},
 		},
 	}
 
@@ -86,7 +165,9 @@ func TestHandler_NotJSON_PassesThrough(t *testing.T) {
 	rr := doRequest(t, h, "GET", "/products/iphonex64s/positions")
 
 	assert.Equal(t, http.StatusOK, rr.Code)
-	assert.Equal(t, "hello", rr.Body.String())
+
+	out := decodeJSON(t, rr.Body.Bytes())
+	assert.Equal(t, []interface{}{}, out["positions"])
 }
 
 func TestHandler_JSONSuccess_AddsDefaults(t *testing.T) {