feat: include origin error message into serialization error (fastify#4601)

Author: ivan-tymoshenko

lib/error-handler.js

@@ -11,7 +11,8 @@ const {
 } = require('./symbols.js')
 
 const {
-  FST_ERR_REP_INVALID_PAYLOAD_TYPE
+  FST_ERR_REP_INVALID_PAYLOAD_TYPE,
+  FST_ERR_FAILED_ERROR_SERIALIZATION
 } = require('./errors')
 
 const { getSchemaSerializer } = require('./schemas')
@@ -113,11 +114,7 @@ function fallbackErrorHandler (error, reply, cb) {
     // error is always FST_ERR_SCH_SERIALIZATION_BUILD because this is called from route/compileSchemasForSerialization
     reply.log.error({ err, statusCode: res.statusCode }, 'The serializer for the given status code failed')
     reply.code(500)
-    payload = serializeError({
-      error: statusCodes['500'],
-      message: err.message,
-      statusCode: 500
-    })
+    payload = serializeError(new FST_ERR_FAILED_ERROR_SERIALIZATION(err.message, error.message))
   }
 
   if (typeof payload !== 'string' && !Buffer.isBuffer(payload)) {

lib/errors.js

@@ -214,6 +214,10 @@ const codes = {
     'FST_ERR_BAD_TRAILER_VALUE',
     "Called reply.trailer('%s', fn) with an invalid type: %s. Expected a function."
   ),
+  FST_ERR_FAILED_ERROR_SERIALIZATION: createError(
+    'FST_ERR_FAILED_ERROR_SERIALIZATION',
+    'Failed to serialize an error. Error: %s. Original error: %s'
+  ),
   FST_ERR_MISSING_SERIALIZATION_FN: createError(
     'FST_ERR_MISSING_SERIALIZATION_FN',
     'Missing serialization function. Key "%s"'

test/schema-serialization.test.js

@@ -833,8 +833,9 @@ test('do not crash if status code serializer errors', async t => {
   t.equal(res.statusCode, 500)
   t.same(res.json(), {
     statusCode: 500,
-    error: 'Internal Server Error',
-    message: '"code" is required!'
+    code: 'FST_ERR_FAILED_ERROR_SERIALIZATION',
+    message: 'Failed to serialize an error. Error: "code" is required!. ' +
+      'Original error: querystring must have required property \'foo\''
   })
 })
 

types/errors.d.ts

@@ -28,6 +28,7 @@ export type FastifyErrorCodes = Record<
 'FST_ERR_BAD_STATUS_CODE'|
 'FST_ERR_BAD_TRAILER_NAME' |
 'FST_ERR_BAD_TRAILER_VALUE' |
+'FST_ERR_FAILED_ERROR_SERIALIZATION' |
 'FST_ERR_MISSING_SERIALIZATION_FN' |
 'FST_ERR_REQ_INVALID_VALIDATION_INVOCATION' |
 'FST_ERR_SCH_MISSING_ID' |