Return custom error if a key does not exist

pkg/modules/keyvalue/error/error.go

@@ -0,0 +1,27 @@
+// Vikunja is a to-do list application to facilitate your life.
+// Copyright 2018-2020 Vikunja and contributors. All rights reserved.
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package error
+
+import "fmt"
+
+type ErrValueNotFoundForKey struct {
+	Key string
+}
+
+func (e *ErrValueNotFoundForKey) Error() string {
+	return fmt.Sprintf("could not find value for key %s", e.Key)
+}

pkg/modules/keyvalue/memory/memory.go

@@ -17,7 +17,10 @@
 
 package memory
 
-import "sync"
+import (
+	e "code.vikunja.io/api/pkg/modules/keyvalue/error"
+	"sync"
+)
 
 // Storage is the memory implementation of a storage backend
 type Storage struct {
@@ -44,7 +47,14 @@ func (s *Storage) Put(key string, value interface{}) (err error) {
 func (s *Storage) Get(key string) (value interface{}, err error) {
 	s.mutex.Lock()
 	defer s.mutex.Unlock()
-	return s.store[key], nil
+
+	var exists bool
+	value, exists = s.store[key]
+	if !exists {
+		return nil, &e.ErrValueNotFoundForKey{Key: key}
+	}
+
+	return
 }
 
 // Del removes a saved value from a memory storage

pkg/modules/keyvalue/redis/redis.go

@@ -18,6 +18,7 @@
 package redis
 
 import (
+	e "code.vikunja.io/api/pkg/modules/keyvalue/error"
 	"code.vikunja.io/api/pkg/red"
 	"encoding/json"
 	"github.com/go-redis/redis/v7"
@@ -51,6 +52,9 @@ func (s *Storage) Put(key string, value interface{}) (err error) {
 func (s *Storage) Get(key string) (value interface{}, err error) {
 	b, err := s.client.Get(key).Bytes()
 	if err != nil {
+		if err == redis.Nil {
+			return nil, &e.ErrValueNotFoundForKey{Key: key}
+		}
 		return nil, err
 	}