Error handling#

Mesh Gateway will forward all errors (resolvers and sources) to the end client by default.

This page will guide you in masking the errors and puts the proper error handling practices in your additionalResolvers.

Enabling Errors masking#

To enable error masking on your Mesh Gateway:

first, update your configuration as follows:

.meshrc.yaml

sources:
 # ...
transforms:
 # ...
additionalEnvelopPlugins: "./envelopPlugins"

Configure the useMaskedErrors() Envelop plugin

envelopPlugins.ts

import { useMaskedErrors, PluginOrDisabledPlugin } from "@envelop/core"

const plugins: PluginOrDisabledPlugin = [
 useMaskedErrors({
 errorMessage: 'Something went wrong.'
 }),
]

export default plugins

Important: the useMaskedErrors() plugin should always put last in the plugin list (example: to avoid masking errors to the useSentry() plugin

Custom error formatting#

Envelop allows you to provide your error formatting function as follow:

envelopPlugins.ts

import { useMaskedErrors, PluginOrDisabledPlugin } from "@envelop/core"

export const formatError: FormatErrorHandler = err => {
 if (err.originalError && err.originalError instanceof EnvelopError === false) {
 return new GraphQLError('Sorry, something went wrong.');
 }

 return err;
};

const plugins: PluginOrDisabledPlugin = [
 useMaskedErrors({
 errorMessage: 'Something went wrong.',
 formatError
 }),
]

export default plugins

This can be helpful, for example, to provide different error types based on a Source.

Custom resolvers error handling#

All errors will be hidden from the end-user when error masking is enabled.

However, some might want to throw specific visible errors.

To make an error visible, leverage the GraphQLYogaError Yoga error class as follows:

additionalResolvers.ts

import { GraphQLYogaError } from '@graphql-yoga/node'

import { Resolvers } from './.mesh'

const resolvers: Resolvers = {
 Book: {
 author: {
 selectionSet: /* GraphQL */`
 {
 authorId
 }
 `,
 resolve: async (root, _args, context, info) => {
 const result = await context.Authors.Query.authors_v1_AuthorsService_GetAuthor({
 root,
 args: {
 input: {
 id: root.authorId,
 }
 },
 context,
 info,
 })
 if (!result) {
 throw new GraphQLYogaError(
 `Author with id '${root.authorId}' not found.`,
 // error extensions
 {
 code: 'AUTHOR_NOT_FOUND',
 // complex values
 bookId: root.id,
 authorId: root.authorId,
 },
 )
 } else {
 return result
 }
 }
 }
 },
}