fix: allow empty json body

The json middleware crashes when it receives an empty string from req.chunk
This causes JSON.parse() to throw an exception since it does not accept empty strings

Author: fernando7jr

src/index.ts

@@ -36,7 +36,7 @@ const custom =
 
 const json = () => async (req: ReqWithBody, res: Response, next: NextFunction) => {
   if (hasBody(req.method)) {
-    req.body = await p((x) => JSON.parse(x.toString()))(req, res, next)
+    req.body = await p((x) => x ? JSON.parse(x.toString()) : {})(req, res, next)
     next()
   } else next()
 }

test.ts

@@ -22,6 +22,25 @@ test('should parse JSON body', async () => {
   }).expect(200, { hello: 'world' })
 })
 
+test('should ignore JSON empty body', async () => {
+  const server = createServer(async (req: ReqWithBody, res) => {
+    await json()(req, res, (err) => void err && console.log(err))
+
+    res.setHeader('Content-Type', 'application/json')
+
+    res.end(JSON.stringify({ok: true}));
+  })
+
+  await makeFetch(server)('/', {
+    body: '',
+    method: 'POST',
+    headers: {
+      Accept: 'application/json',
+      'Content-Type': 'application/json',
+    },
+  }).expect(200, { ok: true })
+})
+
 test('should parse json body with no content-type headers', async () => {
   const server = createServer(async (req: ReqWithBody, res) => {
     await json()(req, res, (err) => void err && console.log(err))