implement file count limit

Author: talentlessguy

src/index.ts

@@ -91,10 +91,13 @@ const getBoundary = (contentType: string) => {
   return match ? `--${match[1]}` : null
 }
 
-const parseMultipart = (body: string, boundary: string) => {
+const parseMultipart = (body: string, boundary: string, { fileCountLimit }: MultipartOptions) => {
   // Split the body into an array of parts
   const parts = body.split(new RegExp(`${boundary}(--)?`)).filter((part) => !!part && /content-disposition/i.test(part))
   const parsedBody: Record<string, (File | string)[]> = {}
+
+  if (fileCountLimit && parts.length > fileCountLimit) throw new Error(`Too many files. Limit: ${fileCountLimit}`)
+
   // Parse each part into a form data object
   // biome-ignore lint/complexity/noForEach: <explanation>
   parts.forEach((part) => {
@@ -126,13 +129,13 @@ type MultipartOptions = Partial<{
 }>
 
 const multipart =
-  (opts: MultipartOptions = {}) =>
+  ({ limit, errorFn, ...opts }: MultipartOptions & ParserOptions = {}) =>
     async (req: ReqWithBody, res: Response, next: NextFunction) => {
       if (hasBody(req.method!)) {
         req.body = await p((x) => {
           const boundary = getBoundary(req.headers['content-type']!)
-          if (boundary) return parseMultipart(x, boundary)
-        })(req, res, next)
+          if (boundary) return parseMultipart(x, boundary, opts)
+        }, limit, errorFn)(req, res, next)
         next()
       } else next()
     }

test.ts

@@ -442,4 +442,23 @@ test('should throw on limit with custom error message', async () => {
   }).expect(413, 'Payload too large. Limit: 1KB')
 })
 
+test('should throw multipart if amount of files exceeds limit', async () => {
+  const server = createServer(async (req: ReqWithBody, res) => {
+    await multipart({ fileCountLimit: 1 })(req, res, (err) => {
+      if (err) res.writeHead(413).end(err.message)
+      else res.end(req.body)
+    })
+  })
+
+  const fd = new FormData()
+
+  fd.set('file1', new File(['hello world'], 'hello.txt', { type: 'text/plain' }))
+  fd.set('file2', new File(['bye world'], 'bye.txt', { type: 'text/plain' }))
+
+  await makeFetch(server)('/', {
+    body: fd,
+    method: 'POST',
+  }).expect(413, 'Too many files. Limit: 1')
+})
+
 test.run()