Return json on 500 error from API (go-gitea#11574)

* add API specific InternalServerError()

Co-authored-by: zeripath <art27@cantab.net>

* return 500 error msg only if not Production mode

* Revert "return 500 error msg only if not Production mode"

This reverts commit 8467b2c.

* InternalServerError

Co-authored-by: zeripath <art27@cantab.net>

modules/context/api.go

@@ -7,6 +7,7 @@ package context
 
 import (
 	"fmt"
+	"net/http"
 	"net/url"
 	"strings"
 
@@ -64,18 +65,18 @@ type APINotFound struct{}
 // swagger:response redirect
 type APIRedirect struct{}
 
-// Error responses error message to client with given message.
+// Error responds with an error message to client with given obj as the message.
 // If status is 500, also it prints error to log.
 func (ctx *APIContext) Error(status int, title string, obj interface{}) {
 	var message string
 	if err, ok := obj.(error); ok {
 		message = err.Error()
 	} else {
-		message = obj.(string)
+		message = fmt.Sprintf("%s", obj)
 	}
 
-	if status == 500 {
-		log.Error("%s: %s", title, message)
+	if status == http.StatusInternalServerError {
+		log.ErrorWithSkip(1, "%s: %s", title, message)
 	}
 
 	ctx.JSON(status, APIError{
@@ -84,6 +85,22 @@ func (ctx *APIContext) Error(status int, title string, obj interface{}) {
 	})
 }
 
+// InternalServerError responds with an error message to the client with the error as a message
+// and the file and line of the caller.
+func (ctx *APIContext) InternalServerError(err error) {
+	log.ErrorWithSkip(1, "InternalServerError: %v", err)
+
+	var message string
+	if macaron.Env != macaron.PROD {
+		message = err.Error()
+	}
+
+	ctx.JSON(http.StatusInternalServerError, APIError{
+		Message: message,
+		URL:     setting.API.SwaggerURL,
+	})
+}
+
 func genAPILinks(curURL *url.URL, total, pageSize, curPage int) []string {
 	page := NewPagination(total, pageSize, curPage, 0)
 	paginater := page.Paginater