Fix type assertion error in avatar upload provider with logging and graceful recovery

Co-authored-by: kolaente <13721712+kolaente@users.noreply.github.com>

Author: Copilot

pkg/modules/avatar/upload/upload.go

@@ -18,6 +18,7 @@ package upload
 
 import (
 	"bytes"
+	"fmt"
 	"image"
 	"image/png"
 	"io"
@@ -56,6 +57,11 @@ func (p *Provider) GetAvatar(u *user.User, size int64) (avatar []byte, mimeType
 	result, err := keyvalue.Remember(cacheKey, func() (any, error) {
 		log.Debugf("Uploaded avatar for user %d and size %d not cached, resizing and caching.", u.ID, size)
 
+		// Check if user has an avatar file ID
+		if u.AvatarFileID == 0 {
+			return nil, fmt.Errorf("user %d has no avatar file", u.ID)
+		}
+
 		// If we get this far, the avatar is either not cached at all or not in this size
 		f := &files.File{ID: u.AvatarFileID}
 		if err := f.LoadFileByID(); err != nil {
@@ -92,7 +98,20 @@ func (p *Provider) GetAvatar(u *user.User, size int64) (avatar []byte, mimeType
 		return nil, "", err
 	}
 
-	cachedAvatar := result.(CachedAvatar)
+	// Safe type assertion to handle cases where cached data might be corrupted or in legacy format
+	cachedAvatar, ok := result.(CachedAvatar)
+	if !ok {
+		// Log the type mismatch with the actual stored value for debugging
+		log.Errorf("Invalid cached avatar type for user %d, size %d. Expected CachedAvatar, got %T with value: %+v. Clearing cache and regenerating.", u.ID, size, result, result)
+		
+		// Clear the invalid cache entry
+		if err := keyvalue.Del(cacheKey); err != nil {
+			log.Errorf("Failed to clear invalid cache entry for key %s: %v", cacheKey, err)
+		}
+		
+		// Regenerate the avatar by calling the function again (without the corrupted cache)
+		return p.GetAvatar(u, size)
+	}
 
 	return cachedAvatar.Content, cachedAvatar.MimeType, nil
 }

pkg/modules/avatar/upload/upload_test.go

@@ -0,0 +1,94 @@
+// Vikunja is a to-do list application to facilitate your life.
+// Copyright 2018-present 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 Affero 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 Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+package upload
+
+import (
+	"os"
+	"testing"
+
+	"code.vikunja.io/api/pkg/log"
+	"code.vikunja.io/api/pkg/modules/keyvalue"
+	"code.vikunja.io/api/pkg/user"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// TestMain initializes the test environment
+func TestMain(m *testing.M) {
+	// Initialize logger for tests
+	log.InitLogger()
+	
+	os.Exit(m.Run())
+}
+
+func TestGetAvatar_HandlesInvalidCachedType(t *testing.T) {
+	// Initialize storage for testing
+	keyvalue.InitStorage()
+	
+	provider := &Provider{}
+	
+	// Create a test user
+	testUser := &user.User{
+		ID:           999999, // Use a high ID to avoid conflicts
+		AvatarFileID: 0,      // No avatar file ID to avoid actual file operations
+	}
+
+	// Simulate corrupted cached data by storing a string instead of CachedAvatar
+	cacheKey := CacheKeyPrefix + "999999_64"
+	err := keyvalue.Put(cacheKey, "corrupted_string_data")
+	require.NoError(t, err)
+
+	// This should not panic but should handle the type assertion gracefully
+	// and return an error (since there's no actual avatar file)
+	avatar, mimeType, err := provider.GetAvatar(testUser, 64)
+
+	// The function should handle the type assertion failure gracefully
+	// and attempt to regenerate the avatar (which will fail due to no file)
+	assert.Error(t, err)
+	assert.Nil(t, avatar)
+	assert.Empty(t, mimeType)
+}
+
+func TestGetAvatar_HandlesValidCachedType(t *testing.T) {
+	// Initialize storage for testing
+	keyvalue.InitStorage()
+	
+	provider := &Provider{}
+	
+	// Create a test user
+	testUser := &user.User{
+		ID:           888888, // Use a different ID to avoid cache conflicts
+		AvatarFileID: 0,
+	}
+
+	// Store a valid cached avatar
+	cacheKey := CacheKeyPrefix + "888888_32"
+	validCachedAvatar := CachedAvatar{
+		Content:  []byte("fake_image_data"),
+		MimeType: "image/png",
+	}
+	err := keyvalue.Put(cacheKey, validCachedAvatar)
+	require.NoError(t, err)
+
+	// This should work correctly with the valid cached data
+	avatar, mimeType, err := provider.GetAvatar(testUser, 32)
+
+	// Should return the cached data successfully
+	assert.NoError(t, err)
+	assert.Equal(t, []byte("fake_image_data"), avatar)
+	assert.Equal(t, "image/png", mimeType)
+}