fix: re-thrown error crash with async handler and sync custom error h…

…andler (#4488)

lib/wrapThenable.js

@@ -35,7 +35,13 @@ function wrapThenable (thenable, reply) {
     }
 
     reply[kReplyIsError] = true
-    reply.send(err)
+
+    // try-catch allow to re-throw error in error handler for async handler
+    try {
+      reply.send(err)
+    } catch (err) {
+      reply.send(err)
+    }
   })
 }
 

test/reply-error.test.js

@@ -514,6 +514,34 @@ test('error thrown by custom error handler routes to default error handler', t =
   })
 })
 
+// Refs: https://github.com/fastify/fastify/pull/4484#issuecomment-1367301750
+test('allow re-thrown error to default error handler when route handler is async and error handler is sync', t => {
+  t.plan(4)
+  const fastify = Fastify()
+
+  fastify.setErrorHandler(function (error) {
+    t.equal(error.message, 'kaboom')
+    throw Error('kabong')
+  })
+
+  fastify.get('/', async function () {
+    throw Error('kaboom')
+  })
+
+  fastify.inject({
+    url: '/',
+    method: 'GET'
+  }, (err, res) => {
+    t.error(err)
+    t.equal(res.statusCode, 500)
+    t.same(JSON.parse(res.payload), {
+      error: statusCodes['500'],
+      message: 'kabong',
+      statusCode: 500
+    })
+  })
+})
+
 // Issue 2078 https://github.com/fastify/fastify/issues/2078
 // Supported error code list: http://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml
 const invalidErrorCodes = [