fix: detect requests without body correctly (#5290)

* fix: detect requests without body correctly

if a request goes through an edge function the content-length header
will not be set and instead the transfer-enconding is set to chunked.

* chore: use header for better readability

* chore: add test

* chore: change to isNan

Co-authored-by: kodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>

src/lib/functions/server.mjs

@@ -41,6 +41,14 @@ const buildClientContext = function (headers) {
   }
 }
 
+const hasBody = (req) =>
+  // copied from is-type package
+  // eslint-disable-next-line unicorn/prefer-number-properties
+  (req.header('transfer-encoding') !== undefined || !isNaN(req.header('content-length'))) &&
+  // we expect a string or a buffer, because we use the two bodyParsers(text, raw) from express
+  // eslint-disable-next-line n/prefer-global/buffer
+  (typeof req.body === 'string' || Buffer.isBuffer(req.body))
+
 export const createHandler = function (options) {
   const { config, functionsRegistry } = options
 
@@ -62,18 +70,21 @@ export const createHandler = function (options) {
       return
     }
 
-    const isBase64Encoded = shouldBase64Encode(request.headers['content-type'])
-    const body = request.get('content-length') ? request.body.toString(isBase64Encoded ? 'base64' : 'utf8') : undefined
+    const isBase64Encoded = shouldBase64Encode(request.header('content-type'))
+    let body
+    if (hasBody(request)) {
+      body = request.body.toString(isBase64Encoded ? 'base64' : 'utf8')
+    }
 
-    let remoteAddress = request.get('x-forwarded-for') || request.connection.remoteAddress || ''
+    let remoteAddress = request.header('x-forwarded-for') || request.connection.remoteAddress || ''
     remoteAddress = remoteAddress
       .split(remoteAddress.includes('.') ? ':' : ',')
       .pop()
       .trim()
 
     let requestPath = request.path
-    if (request.get('x-netlify-original-pathname')) {
-      requestPath = request.get('x-netlify-original-pathname')
+    if (request.header('x-netlify-original-pathname')) {
+      requestPath = request.header('x-netlify-original-pathname')
       delete request.headers['x-netlify-original-pathname']
     }
     const queryParams = Object.entries(request.query).reduce(

tests/integration/400.command.dev.test.cjs

@@ -287,6 +287,57 @@ test('should pass body to functions event for POST requests when redirecting', a
   })
 })
 
+test('should pass body to functions event for POST requests with passthrough edge function', async (t) => {
+  await withSiteBuilder('site-with-post-echo-function', async (builder) => {
+    builder
+      .withNetlifyToml({
+        config: {
+          functions: { directory: 'functions' },
+          redirects: [{ from: '/api/*', to: '/.netlify/functions/:splat', status: 200 }],
+          edge_functions: [
+            {
+              function: 'passthrough',
+              path: '/*',
+            },
+          ],
+        },
+      })
+      .withEdgeFunction({
+        name: 'passthrough',
+        handler: async (_, context) => context.next(),
+      })
+      .withFunction({
+        path: 'echo.js',
+        handler: async (event) => ({
+          statusCode: 200,
+          body: JSON.stringify(event),
+        }),
+      })
+
+    await builder.buildAsync()
+
+    await withDevServer({ cwd: builder.directory }, async (server) => {
+      const response = await got
+        .post(`${server.url}/api/echo?ding=dong`, {
+          headers: {
+            'content-type': 'application/x-www-form-urlencoded',
+          },
+          body: 'some=thing',
+        })
+        .json()
+
+      t.is(response.body, 'some=thing')
+      t.is(response.headers.host, `${server.host}:${server.port}`)
+      t.is(response.headers['content-type'], 'application/x-www-form-urlencoded')
+      t.is(response.headers['transfer-encoding'], 'chunked')
+      t.is(response.httpMethod, 'POST')
+      t.is(response.isBase64Encoded, false)
+      t.is(response.path, '/api/echo')
+      t.deepEqual(response.queryStringParameters, { ding: 'dong' })
+    })
+  })
+})
+
 test('should return an empty body for a function with no body when redirecting', async (t) => {
   await withSiteBuilder('site-with-no-body-function', async (builder) => {
     builder