Handle contentType not being set in netlify dev

src/commands/dev/index.js

@@ -214,11 +214,11 @@ async function startProxy(settings = {}, addonUrls, configPath, projectDir, func
 
       if (match) return serveRedirect(req, res, proxy, match, options)
 
-      const ct = req.headers['content-type'] ? contentType.parse(req) : {}
+      const ct = req.headers['content-type'] ? contentType.parse(req).type : ''
       if (
         req.method === 'POST' &&
         !isInternal(req.url) &&
-        (ct.type.endsWith('/x-www-form-urlencoded') || ct.type === 'multipart/form-data')
+        (ct.endsWith('/x-www-form-urlencoded') || ct === 'multipart/form-data')
       ) {
         return proxy.web(req, res, { target: functionsServer })
       }
@@ -338,12 +338,12 @@ async function serveRedirect(req, res, proxy, match, options) {
       return handler(req, res, {})
     }
 
-    const ct = req.headers['content-type'] ? contentType.parse(req) : {}
+    const ct = req.headers['content-type'] ? contentType.parse(req).type : ''
     if (
       req.method === 'POST' &&
       !isInternal(req.url) &&
       !isInternal(destURL) &&
-      (ct.type.endsWith('/x-www-form-urlencoded') || ct.type === 'multipart/form-data')
+      (ct.endsWith('/x-www-form-urlencoded') || ct === 'multipart/form-data')
     ) {
       return proxy.web(req, res, { target: options.functionsServer })
     }

tests/command.dev.test.js

@@ -764,3 +764,42 @@ test('should redirect requests to an external server', async t => {
     server.close()
   })
 })
+
+test('should redirect POST request if content-type is missing', async t => {
+  await withSiteBuilder('site-with-post-no-content-type', async builder => {
+    builder.withNetlifyToml({
+      config: {
+        build: { functions: 'functions' },
+        redirects: [{ from: '/api/*', to: '/other/:splat', status: 200 }],
+      },
+    })
+
+    await builder.buildAsync()
+
+    await withDevServer({ cwd: builder.directory }, async server => {
+      // we use http.request since fetch automatically sends a content-type header
+      const http = require('http')
+      const options = {
+        host: server.host,
+        port: server.port,
+        path: '/api/echo',
+        method: 'POST',
+      }
+      let data = ''
+      await new Promise(resolve => {
+        const callback = response => {
+          response.on('data', chunk => {
+            data += chunk
+          })
+          response.on('end', resolve)
+        }
+        const req = http.request(options, callback)
+        req.write('param=value')
+        req.end()
+      })
+
+      // we're testing Netlify Dev didn't crash
+      t.is(data, 'Method Not Allowed')
+    })
+  })
+})