Allow custom error handling via HandleErrResponse (#27)

nethttp/handler.go

@@ -5,7 +5,6 @@ import (
 	"net/http"
 	"reflect"
 
-	"github.com/swaggest/openapi-go/openapi3"
 	"github.com/swaggest/rest"
 	"github.com/swaggest/usecase"
 	"github.com/swaggest/usecase/status"
@@ -22,6 +21,7 @@ func NewHandler(useCase usecase.Interactor, options ...func(h *Handler)) *Handle
 	h := &Handler{
 		options: options,
 	}
+	h.HandleErrResponse = h.handleErrResponseDefault
 	h.SetUseCase(useCase)
 
 	return h
@@ -50,8 +50,8 @@ func (h *Handler) SetUseCase(useCase usecase.Interactor) {
 type Handler struct {
 	rest.HandlerTrait
 
-	// OperationAnnotations are called after operation setup and before adding operation to documentation.
-	OperationAnnotations []func(op *openapi3.Operation) error
+	// HandleErrResponse allows control of error response processing.
+	HandleErrResponse func(w http.ResponseWriter, r *http.Request, err error)
 
 	// requestDecoder maps data from http.Request into structured Go input value.
 	requestDecoder RequestDecoder
@@ -123,7 +123,7 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	h.responseEncoder.WriteSuccessfulResponse(w, r, output, h.HandlerTrait)
 }
 
-func (h *Handler) handleErrResponse(w http.ResponseWriter, r *http.Request, err error) {
+func (h *Handler) handleErrResponseDefault(w http.ResponseWriter, r *http.Request, err error) {
 	var (
 		code int
 		er   interface{}
@@ -138,6 +138,16 @@ func (h *Handler) handleErrResponse(w http.ResponseWriter, r *http.Request, err
 	h.responseEncoder.WriteErrResponse(w, r, code, er)
 }
 
+func (h *Handler) handleErrResponse(w http.ResponseWriter, r *http.Request, err error) {
+	if h.HandleErrResponse != nil {
+		h.HandleErrResponse(w, r, err)
+
+		return
+	}
+
+	h.handleErrResponseDefault(w, r, err)
+}
+
 func closeMultipartForm(r *http.Request) {
 	if err := r.MultipartForm.RemoveAll(); err != nil {
 		log.Println(err)

nethttp/handler_test.go

@@ -298,3 +298,37 @@ func TestHandler_ServeHTTP_customMapping(t *testing.T) {
 	assert.Equal(t, http.StatusNoContent, rw.Code)
 	assert.Equal(t, "", rw.Body.String())
 }
+
+func TestOptionsMiddleware(t *testing.T) {
+	u := usecase.NewIOI(nil, nil, func(ctx context.Context, input, output interface{}) error {
+		return errors.New("failed")
+	})
+	h := nethttp.NewHandler(u, func(h *nethttp.Handler) {
+		h.MakeErrResp = func(ctx context.Context, err error) (int, interface{}) {
+			return http.StatusExpectationFailed, struct {
+				Foo string `json:"foo"`
+			}{Foo: err.Error()}
+		}
+	})
+	h.SetResponseEncoder(&response.Encoder{})
+
+	var loggedErr error
+
+	rw := httptest.NewRecorder()
+	req, err := http.NewRequest(http.MethodGet, "/", nil)
+	require.NoError(t, err)
+
+	oh := nethttp.OptionsMiddleware(func(h *nethttp.Handler) {
+		handleErrResponse := h.HandleErrResponse
+		h.HandleErrResponse = func(w http.ResponseWriter, r *http.Request, err error) {
+			assert.Equal(t, req, r)
+			loggedErr = err
+			handleErrResponse(w, r, err)
+		}
+	})(h)
+
+	oh.ServeHTTP(rw, req)
+
+	assert.EqualError(t, loggedErr, "failed")
+	assert.Equal(t, `{"foo":"failed"}`+"\n", rw.Body.String())
+}

nethttp/options.go

@@ -1,13 +1,31 @@
 package nethttp
 
 import (
+	"net/http"
 	"reflect"
 
 	"github.com/swaggest/openapi-go/openapi3"
 	"github.com/swaggest/refl"
 	"github.com/swaggest/rest"
 )
 
+// OptionsMiddleware applies options to encountered nethttp.Handler.
+func OptionsMiddleware(options ...func(h *Handler)) func(h http.Handler) http.Handler {
+	return func(h http.Handler) http.Handler {
+		var rh *Handler
+
+		if HandlerAs(h, &rh) {
+			rh.options = append(rh.options, options...)
+
+			for _, option := range options {
+				option(rh)
+			}
+		}
+
+		return h
+	}
+}
+
 // AnnotateOperation allows customizations of prepared operations.
 func AnnotateOperation(annotations ...func(operation *openapi3.Operation) error) func(h *Handler) {
 	return func(h *Handler) {

trait.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"reflect"
 
+	"github.com/swaggest/openapi-go/openapi3"
 	"github.com/swaggest/refl"
 	"github.com/swaggest/usecase"
 )
@@ -33,6 +34,9 @@ type HandlerTrait struct {
 
 	// RespValidator validates decoded response data.
 	RespValidator Validator
+
+	// OperationAnnotations are called after operation setup and before adding operation to documentation.
+	OperationAnnotations []func(op *openapi3.Operation) error
 }
 
 // RestHandler is a an accessor.