refactor: create Object directly when upload file with URL (#625)

Author: sdjdd

changelog.md

@@ -1,3 +1,9 @@
+# Master
+
+### Internal Changes
+
+- 现在保存通过 `AV.File.withURL` 方法创建的文件等同于直接在 \_File 中添加一行数据，不再自动生成 `mime_type`。
+
 # 4.7.0（2020-07-14）
 
 ### Features

src/file.js

@@ -183,6 +183,7 @@ module.exports = function(AV) {
     file.attributes.url = url;
     //Mark the file is from external source.
     file.attributes.metaData.__source = 'external';
+    file.attributes.metaData.size = 0;
     return file;
   };
 
@@ -595,18 +596,13 @@ module.exports = function(AV) {
             };
             this._previousSave = AVRequest(
               'files',
-              this.attributes.name,
+              null,
               null,
               'post',
               data,
               options
             ).then(response => {
-              this.attributes.name = response.name;
-              this.attributes.url = response.url;
               this.id = response.objectId;
-              if (response.size) {
-                this.attributes.metaData.size = response.size;
-              }
               return this;
             });
           }