Error Link

Handle and inspect errors in your GraphQL network stack.

We recommend reading

before learning about individual links.

Use the onError link to perform custom logic when a

occurs. You pass this link a function that's executed if an operation returns one or more errors:

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import { onError } from "@apollo/client/link/error";
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// Log any GraphQL errors or network error that occurred
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const errorLink = onError(({ graphQLErrors, networkError }) => {
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  if (graphQLErrors)
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    graphQLErrors.forEach(({ message, locations, path }) =>
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      console.log(
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        `[GraphQL error]: Message: ${message}, Location: ${locations}, Path: ${path}`
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      )
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    );
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  if (networkError) console.log(`[Network error]: ${networkError}`);
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});

This function is called after the GraphQL operation completes and execution is moving back up your

link chain

. The function should not return a value unless you want to

retry the operation

Options

The function you provide the onError link is passed an object with the following fields:

Name / Type	Description
`operation` `Operation`	The details of the GraphQL operation that produced an error. See type definition
`response` `ExecutionResult`	The (possibly modified) GraphQL result from the server, passed by the next link down the chain (i.e., the link closer to the terminating link). See type definition
`graphQLErrors` `ReadonlyArray<GraphQLError>`	An array of GraphQL errors that occurred while executing the operation, if any. See type definition
`networkError` `Error \| ServerError \| ServerParseError`	A network error that occurred while attempting to execute the operation, if any.
`forward` `function`	A function that calls the next link down the chain. Calling `return forward(operation)` in your `onError` callback retries the operation , returning a new observable for the upstream link to subscribe to.

An error is passed as a networkError if a link further down the chain called the error callback on the observable. In most cases, graphQLErrors is the errors field of the result from the last next call.

A networkError can contain additional fields, such as a GraphQL object in the case of a failing HTTP status code. In this situation, graphQLErrors is an alias for networkError.result.errors if the property exists.

Context

Persisted Queries

Error Link

Handle and inspect errors in your GraphQL network stack.

Options

`operation`

`response`

`graphQLErrors`

`networkError`

`forward`

Error categorization