unstable_createFileUploadHandler

Node.js 上传处理程序会将带有文件名的部分写入磁盘，以免占用内存，没有文件名的部分将不会被解析。应与另一个上传处理程序组合使用。

例子：

export const action = async ({
  request,
}: ActionFunctionArgs) => {
  const uploadHandler = unstable_composeUploadHandlers(
    unstable_createFileUploadHandler({
      maxPartSize: 5_000_000,
      file: ({ filename }) => filename,
    }),
    // parse everything else into memory
    unstable_createMemoryUploadHandler()
  );
  const formData = await unstable_parseMultipartFormData(
    request,
    uploadHandler
  );

  const file = formData.get("avatar");

  // file is a "NodeOnDiskFile" which implements the "File" API
  // ... etc
};

选项：

Property	Type	Default	Description
avoidFileConflicts	boolean	true	Avoid file conflicts by appending a timestamp on the end of the filename if it already exists on disk
directory	string | Function	os.tmpdir()	The directory to write the upload.
file	Function	() => upload_${random}.${ext}	The name of the file in the directory. Can be a relative path, the directory structure will be created if it does not exist.
maxPartSize	number	3000000	The maximum upload size allowed (in bytes). If the size is exceeded a MaxPartSizeExceededError will be thrown.
filter	Function	OPTIONAL	A function you can write to prevent a file upload from being saved based on filename, content type, or field name. Return false and the file will be ignored.

file 和 directory 的函数 API 相同，接受一个 object 并返回一个 string，接受的对象有 filename、name 和 contentType（都是字符串），返回的 string 就是路径。

filter 函数接受一个 object 并返回一个 boolean（或解析为 boolean 的 promise）。它接受的对象具有 filename、name 和 contentType（均为字符串）。如果您要处理该文件流，则返回的 boolean 为 true。