Add error handler

error/handler.go

@@ -0,0 +1,61 @@
+package error
+
+import (
+	"fmt"
+
+	"github.com/gin-gonic/gin"
+
+	"net/http"
+	"strings"
+	"unicode"
+
+	"gopkg.in/go-playground/validator.v8"
+)
+
+type errorWrapper struct {
+	Error            string `json:"error"`
+	ErrorCode        int    `json:"errorCode"`
+	ErrorDescription string `json:"errorDescription"`
+}
+
+// Handler creates a gin middleware for handling errors.
+func Handler() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		c.Next()
+
+		if len(c.Errors) > 0 {
+			for _, e := range c.Errors {
+				switch e.Type {
+				case gin.ErrorTypeBind:
+					errs := e.Err.(validator.ValidationErrors)
+					var stringErrors []string
+					for _, err := range errs {
+						stringErrors = append(stringErrors, validationErrorToText(err))
+					}
+					writeError(c, strings.Join(stringErrors, "; "))
+				default:
+					writeError(c, e.Err.Error())
+				}
+			}
+		}
+	}
+}
+
+func validationErrorToText(e *validator.FieldError) string {
+	runes := []rune(e.Field)
+	runes[0] = unicode.ToLower(runes[0])
+	fieldName := string(runes)
+	switch e.Tag {
+	case "required":
+		return fmt.Sprintf("Field '%s' is required", fieldName)
+	}
+	return fmt.Sprintf("Field '%s' is not valid", fieldName)
+}
+
+func writeError(ctx *gin.Context, errString string) {
+	status := http.StatusBadRequest
+	if ctx.Writer.Status() != http.StatusOK {
+		status = ctx.Writer.Status()
+	}
+	ctx.JSON(status, &errorWrapper{Error: http.StatusText(status), ErrorCode: status, ErrorDescription: errString})
+}

error/handler_test.go

@@ -0,0 +1,63 @@
+package error
+
+import (
+	"encoding/json"
+	"errors"
+	"io/ioutil"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestDefaultErrorInternal(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	rec := httptest.NewRecorder()
+	ctx, _ := gin.CreateTestContext(rec)
+	ctx.AbortWithError(500, errors.New("something went wrong"))
+
+	Handler()(ctx)
+
+	assertJSONResponse(t, rec, 500, `{"errorCode":500, "errorDescription":"something went wrong", "error":"Internal Server Error"}`)
+}
+
+func TestDefaultErrorBadRequest(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	rec := httptest.NewRecorder()
+	ctx, _ := gin.CreateTestContext(rec)
+	ctx.AbortWithError(400, errors.New("you need todo something"))
+
+	Handler()(ctx)
+
+	assertJSONResponse(t, rec, 400, `{"errorCode":400, "errorDescription":"you need todo something", "error":"Bad Request"}`)
+}
+
+type testValidate struct {
+	Username string `json:"username" binding:"required"`
+	Mail     string `json:"mail" binding:"email"`
+}
+
+func TestValidationError(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	rec := httptest.NewRecorder()
+	ctx, _ := gin.CreateTestContext(rec)
+	ctx.Request = httptest.NewRequest("GET", "/uri", nil)
+
+	assert.NotNil(t, ctx.Bind(&testValidate{}))
+	Handler()(ctx)
+
+	err := new(errorWrapper)
+	json.NewDecoder(rec.Body).Decode(err)
+	assert.Equal(t, 400, rec.Code)
+	assert.Equal(t, "Bad Request", err.Error)
+	assert.Equal(t, 400, err.ErrorCode)
+	assert.Contains(t, err.ErrorDescription, "Field 'username' is required")
+	assert.Contains(t, err.ErrorDescription, "Field 'mail' is not valid")
+}
+
+func assertJSONResponse(t *testing.T, rec *httptest.ResponseRecorder, code int, json string) {
+	bytes, _ := ioutil.ReadAll(rec.Body)
+	assert.Equal(t, code, rec.Code)
+	assert.JSONEq(t, json, string(bytes))
+}