facebook/relay · error

Relay Environment Configuration Error (dev only): `@required

Error message

Relay Environment Configuration Error (dev only): `@required(action: LOG)` requires that the Relay Environment be configured with a `relayFieldLogger`.

What it means

@required(action: LOG) fields report missing-field events through the environment's relayFieldLogger. The default logger deliberately throws in __DEV__ when such an event arrives, telling the developer the environment was never configured with a real logger; in production it silently no-ops.

Source

Thrown at packages/relay-runtime/store/defaultRelayFieldLogger.js:18

/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow strict-local
 * @format
 * @oncall relay
 */

'use strict';

import type {RelayFieldLogger} from './RelayStoreTypes';

const defaultRelayFieldLogger: RelayFieldLogger = event => {
  if (__DEV__ && event.kind === 'missing_required_field.log') {
    throw new Error(
      'Relay Environment Configuration Error (dev only): `@required(action: LOG)` requires that the Relay Environment be configured with a `relayFieldLogger`.',
    );
  }
};

module.exports = defaultRelayFieldLogger;

View on GitHub (pinned to 668b1b85e0)

Solutions

1. Pass relayFieldLogger to the Relay Environment constructor with a handler for missing_required_field.log events
2. Import and wire defaultRelayFieldLogger replacement, e.g. from relay-runtime/store/RelayDefaultFieldLogger (or your own)
3. If the throw is intentional dev noise, confirm __DEV__ flag and add the logger before data reads
4. Remove or downgrade @required(action: LOG) if logging isn't actually wanted

Example fix

// before
const env = new Environment({network, store});
// after
const env = new Environment({network, store, relayFieldLogger: myFieldLogger});

if (__DEV__ && env.getNetwork == null) {/*...*/}
// Before reading data in dev, assert the environment was built with a field logger:
console.assert(envConfig.relayFieldLogger != null, 'Configure relayFieldLogger for @required(action: LOG)');

null

try {
  lookupData();
} catch (e) {
  if (String(e.message).includes('relayFieldLogger')) {
    console.error('Environment missing relayFieldLogger; configure it for @required(action: LOG)');
  } else throw e;
}

When it happens

Trigger: Reading a snapshot where a @required(action: LOG) field is missing while the Environment was created without passing relayFieldLogger to the constructor (and the app is running in development).

Common situations: Creating a new Environment in tests or Storybook with only a network/store and forgetting relayFieldLogger; adding @required(action: LOG) to a fragment without updating environment setup; dev-only builds surfacing what production hides.

Understand the failure class

Background: "environment variable is not set" and "Missing keys in environment" errors: what missing required env var messages mean and how to fix them — this error's family across 28 libraries.

Related errors

• BabelPluginRelay: Expected plugin context to include "types"
• Babel state is missing expected file name
• RelayObservable: Expected pollInterval to be positive, got:
• BabelPluginRelay: Expected exactly one definition per graphq
• BabelPluginRelay: Expected a fragment, mutation, query, or s

AI-assisted analysis of facebook/relay@668b1b85e0 (2026-09-02). Data as JSON: /api/errors/6539f64048505363. Report an issue: GitHub.