Fix: while placeholder file got conflict, original file might be deleted

pkg/filesystem/driver/local/handler.go

@@ -267,6 +267,10 @@ func (handler Driver) Source(
 
 // Token 获取上传策略和认证Token，本地策略直接返回空值
 func (handler Driver) Token(ctx context.Context, ttl int64, uploadSession *serializer.UploadSession, file fsctx.FileHeader) (*serializer.UploadCredential, error) {
+	if util.Exists(uploadSession.SavePath) {
+		return nil, errors.New("placeholder file already exist")
+	}
+
 	return &serializer.UploadCredential{
 		SessionID: uploadSession.Key,
 		ChunkSize: handler.Policy.OptionsSerialized.ChunkSize,

pkg/filesystem/upload.go

@@ -178,7 +178,7 @@ func (fs *FileSystem) CreateUploadSession(ctx context.Context, file *fsctx.FileS
 		fs.Use("AfterUpload", HookClearFileHeaderSize)
 	}
 
-	fs.Use("AfterUpload", GenericAfterUpload)
+	// 验证文件规格
 	if err := fs.Upload(ctx, file); err != nil {
 		return nil, err
 	}
@@ -201,6 +201,12 @@ func (fs *FileSystem) CreateUploadSession(ctx context.Context, file *fsctx.FileS
 		return nil, err
 	}
 
+	// 创建占位符
+	fs.Use("AfterUpload", GenericAfterUpload)
+	if err := fs.Upload(ctx, file); err != nil {
+		return nil, err
+	}
+
 	// 创建回调会话
 	err = cache.Set(
 		UploadSessionCachePrefix+callbackKey,

pkg/serializer/error.go

@@ -54,6 +54,8 @@ const (
 	CodeNoPermissionErr = 403
 	// CodeNotFound 资源未找到
 	CodeNotFound = 404
+	// CodeConflict 资源冲突
+	CodeConflict = 409
 	// CodeUploadFailed 上传出错
 	CodeUploadFailed = 40002
 	// CodeCredentialInvalid 凭证无效

service/explorer/slave.go

@@ -13,6 +13,7 @@ import (
 	"github.com/cloudreve/Cloudreve/v3/pkg/serializer"
 	"github.com/cloudreve/Cloudreve/v3/pkg/task"
 	"github.com/cloudreve/Cloudreve/v3/pkg/task/slavetask"
+	"github.com/cloudreve/Cloudreve/v3/pkg/util"
 	"github.com/gin-gonic/gin"
 	"github.com/jinzhu/gorm"
 	"net/http"
@@ -172,6 +173,10 @@ type SlaveCreateUploadSessionService struct {
 
 // Create 从机创建上传会话
 func (service *SlaveCreateUploadSessionService) Create(ctx context.Context, c *gin.Context) serializer.Response {
+	if util.Exists(service.Session.SavePath) {
+		return serializer.Err(serializer.CodeConflict, "placeholder file already exist", nil)
+	}
+
 	err := cache.Set(
 		filesystem.UploadSessionCachePrefix+service.Session.Key,
 		service.Session,