feat: add rest.WithCustomCors to let caller customize the response (#1274)

rest/internal/cors/handlers.go

@@ -23,9 +23,12 @@ const (
 
 // NotAllowedHandler handles cross domain not allowed requests.
 // At most one origin can be specified, other origins are ignored if given, default to be *.
-func NotAllowedHandler(origins ...string) http.Handler {
+func NotAllowedHandler(fn func(w http.ResponseWriter), origins ...string) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		checkAndSetHeaders(w, r, origins)
+		if fn != nil {
+			fn(w)
+		}
 
 		if r.Method != http.MethodOptions {
 			w.WriteHeader(http.StatusNotFound)
@@ -36,10 +39,13 @@ func NotAllowedHandler(origins ...string) http.Handler {
 }
 
 // Middleware returns a middleware that adds CORS headers to the response.
-func Middleware(origins ...string) func(http.HandlerFunc) http.HandlerFunc {
+func Middleware(fn func(w http.ResponseWriter), origins ...string) func(http.HandlerFunc) http.HandlerFunc {
 	return func(next http.HandlerFunc) http.HandlerFunc {
 		return func(w http.ResponseWriter, r *http.Request) {
 			checkAndSetHeaders(w, r, origins)
+			if fn != nil {
+				fn(w)
+			}
 
 			if r.Method == http.MethodOptions {
 				w.WriteHeader(http.StatusNoContent)

rest/internal/cors/handlers_test.go

@@ -62,7 +62,7 @@ func TestCorsHandlerWithOrigins(t *testing.T) {
 				r := httptest.NewRequest(method, "http://localhost", nil)
 				r.Header.Set(originHeader, test.reqOrigin)
 				w := httptest.NewRecorder()
-				handler := NotAllowedHandler(test.origins...)
+				handler := NotAllowedHandler(nil, test.origins...)
 				handler.ServeHTTP(w, r)
 				if method == http.MethodOptions {
 					assert.Equal(t, http.StatusNoContent, w.Result().StatusCode)
@@ -71,6 +71,22 @@ func TestCorsHandlerWithOrigins(t *testing.T) {
 				}
 				assert.Equal(t, test.expect, w.Header().Get(allowOrigin))
 			})
+			t.Run(test.name+"-handler-custom", func(t *testing.T) {
+				r := httptest.NewRequest(method, "http://localhost", nil)
+				r.Header.Set(originHeader, test.reqOrigin)
+				w := httptest.NewRecorder()
+				handler := NotAllowedHandler(func(w http.ResponseWriter) {
+					w.Header().Set("foo", "bar")
+				}, test.origins...)
+				handler.ServeHTTP(w, r)
+				if method == http.MethodOptions {
+					assert.Equal(t, http.StatusNoContent, w.Result().StatusCode)
+				} else {
+					assert.Equal(t, http.StatusNotFound, w.Result().StatusCode)
+				}
+				assert.Equal(t, test.expect, w.Header().Get(allowOrigin))
+				assert.Equal(t, "bar", w.Header().Get("foo"))
+			})
 		}
 	}
 
@@ -81,7 +97,7 @@ func TestCorsHandlerWithOrigins(t *testing.T) {
 				r := httptest.NewRequest(method, "http://localhost", nil)
 				r.Header.Set(originHeader, test.reqOrigin)
 				w := httptest.NewRecorder()
-				handler := Middleware(test.origins...)(func(w http.ResponseWriter, r *http.Request) {
+				handler := Middleware(nil, test.origins...)(func(w http.ResponseWriter, r *http.Request) {
 					w.WriteHeader(http.StatusOK)
 				})
 				handler.ServeHTTP(w, r)
@@ -92,6 +108,24 @@ func TestCorsHandlerWithOrigins(t *testing.T) {
 				}
 				assert.Equal(t, test.expect, w.Header().Get(allowOrigin))
 			})
+			t.Run(test.name+"-middleware-custom", func(t *testing.T) {
+				r := httptest.NewRequest(method, "http://localhost", nil)
+				r.Header.Set(originHeader, test.reqOrigin)
+				w := httptest.NewRecorder()
+				handler := Middleware(func(w http.ResponseWriter) {
+					w.Header().Set("foo", "bar")
+				}, test.origins...)(func(w http.ResponseWriter, r *http.Request) {
+					w.WriteHeader(http.StatusOK)
+				})
+				handler.ServeHTTP(w, r)
+				if method == http.MethodOptions {
+					assert.Equal(t, http.StatusNoContent, w.Result().StatusCode)
+				} else {
+					assert.Equal(t, http.StatusOK, w.Result().StatusCode)
+				}
+				assert.Equal(t, test.expect, w.Header().Get(allowOrigin))
+				assert.Equal(t, "bar", w.Header().Get("foo"))
+			})
 		}
 	}
 }