fix: handle absolute paths correctly with tempFileDir upload option (#14436)

### What?
This PR fixes `tempFileDir` configuration not respecting absolute paths
when `useTempFiles` is enabled for uploads.
### Why?
1. **Absolute paths ignored**: Setting `tempFileDir: '/tmp'` would still
create temp files under the working directory (e.g.,
`/Users/project/tmp/...`) instead of `/tmp/...`
2. **Path duplication**: The default `tempFileDir` could result in
duplicated working directory segments in the path
### How?
Uses `path.resolve()` to handle both cases:
- Absolute paths (e.g., `/tmp`) are returned as-is
- Relative paths (e.g., `tmp`) are resolved against `process.cwd()`
Fixes#12910
---------
Co-authored-by: Jessica Chowdhury <jessica@trbl.design>

Author: sanbrien

docs/upload/overview.mdx

@@ -132,7 +132,7 @@ Upload options are specifiable on a Collection by Collection basis, you can also
 |**`preserveExtension`**| Preserves file extensions with the `safeFileNames` option. Limits file names to 3 characters if `true` or a custom length if a `number`, trimming from the start of the extension. |
 |**`responseOnLimit`**| A `string` that is sent in the Response to a client if the file size limit is exceeded when used with `abortOnLimit`. |
 |**`safeFileNames`**| Set to `true` to strip non-alphanumeric characters except dashes and underscores. Can also be set to a regex to determine what to strip. Defaults to `false`. |
-|**`tempFileDir`**| A `string` path to store temporary files used when the `useTempFiles` option is set to `true`. Defaults to `'./tmp'`. |
+|**`tempFileDir`**| A `string` path to store temporary files used when the `useTempFiles` option is set to `true`. Defaults to `'tmp'` in the current working directory. Supports absolute paths.|
 |**`uploadTimeout`**| A `number` that defines how long to wait for data before aborting, specified in milliseconds. Set to `0` to disable timeout checks. Defaults to `60000`. |
 |**`uriDecodeFileNames`**| Set to `true` to apply uri decoding to file names. Defaults to `false`. |
 |**`useTempFiles`**| Set to `true` to store files to a temporary directory instead of in RAM, reducing memory usage for large files or many files. |

packages/payload/src/config/types.ts

@@ -676,7 +676,7 @@ export type FetchAPIFileUploadOptions = {
  * Used along with the `useTempFiles` option. By default this module uses `'tmp'` folder
  * in the current working directory.
  * You can use trailing slash, but it is not necessary.
- * @default './tmp'
+ * @default 'tmp'
  */
 tempFileDir?: string|undefined
 /**

packages/payload/src/uploads/fetchAPI-multipart/handlers.ts

@@ -21,8 +21,7 @@ type Handler = (
 }
 
 exportconsttempFileHandler: Handler=(options,fieldname,filename)=>{
-constdir=path.normalize(options.tempFileDir!)
-consttempFilePath=path.join(process.cwd(),dir,getTempFilename())
+consttempFilePath=path.resolve(options.tempFileDir!,getTempFilename())
 checkAndMakeDir({createParentPath: true},tempFilePath)
 
 debugLog(options,`Temporary file path is ${tempFilePath}`)

packages/payload/src/uploads/fetchAPI-multipart/index.ts

@@ -17,7 +17,7 @@ const DEFAULT_UPLOAD_OPTIONS: FetchAPIFileUploadOptions = {
 preserveExtension: false,
 responseOnLimit: 'File size limit has been reached',
 safeFileNames: false,
-tempFileDir: path.join(process.cwd(),'tmp'),
+tempFileDir: 'tmp',// Relative path is created inside current workdir.
 uploadTimeout: 60000,
 uriDecodeFileNames: false,
 useTempFiles: false,

packages/payload/src/uploads/fetchAPI-multipart/utilities.ts

@@ -118,7 +118,7 @@ export const checkAndMakeDir: CheckAndMakeDir = (fileUploadOptions, filePath) =>
 returnfalse
 }
 // Check whether folder for the file exists.
-constparentPath=path.dirname(filePath)
+constparentPath=path.dirname(path.resolve(filePath))
 // Create folder if it doesn't exist.
 if(!fs.existsSync(parentPath)){
 fs.mkdirSync(parentPath,{recursive: true})

test/uploads/int.spec.ts

@@ -15,6 +15,8 @@ import type { Enlarge, Media } from './payload-types.js'
 
 // eslint-disable-next-line payload/no-relative-monorepo-imports
 import{getExternalFile}from'../../packages/payload/src/uploads/getExternalFile.js'
+// eslint-disable-next-line payload/no-relative-monorepo-imports
+import{tempFileHandler}from'../../packages/payload/src/uploads/fetchAPI-multipart/handlers.js'
 import{initPayloadInt}from'../__helpers/shared/initPayloadInt.js'
 import{createStreamableFile}from'./createStreamableFile.js'
 import{
@@ -1742,6 +1744,19 @@ describe('Collections - Uploads', () => {
 }
 })
 })
+
+describe('tempFileDir',()=>{
+it.each([
+{dir: '/tmp',expectedPrefix: '/tmp',description: 'absolute path like /tmp'},
+{dir: 'tmp',expectedPrefix: path.join(process.cwd(),'tmp'),description: 'relative path'},
+])('creates temp files in correct location for $description',({ dir, expectedPrefix })=>{
+consthandler=tempFileHandler({tempFileDir: dir},'field','file.png')
+constfilePath=handler.getFilePath()
+
+expect(filePath.startsWith(expectedPrefix)).toBe(true)
+handler.cleanup()
+})
+})
 })
 
 asyncfunctionfileExists(fileName: string): Promise<boolean>{