/**
 * The error message handler is a function that is called when a message is
 * logged or an error is thrown to determine the contents of the error message
 * to be logged or thrown.
 */
export type ErrorMessageHandler = {
    /**
     * @param message - Usually the error message number (as defined in
     * `@apollo/client/invariantErrorCodes.js`).
     * In some edge cases, this can already be a string, that can be passed through
     * as an error message.
     *
     * @param args - The placeholders that can be passed into the error message (pre-stringified).
     * These relate with the `%s` and `%d` [substitution strings](https://developer.mozilla.org/en-US/docs/Web/API/console#using_string_substitutions)
     * in the error message defined in `@apollo/client/invariantErrorCodes.js`.
     *
     * ⚠️ Note that arguments will only be passed in for error messages.
     * For normal log messages, you will get an empty array here and they will directly
     * be passed to `console.log` instead, to have the string substitution done by the
     * engine, as that allows for nicer (and in the case of a browser, interactive)
     * output.
     *
     * @returns The error message to be logged or thrown. If it returns `undefined`,
     * the mechanism will fall back to the default:
     * A link to https://go.apollo.dev/c/err with Apollo Client version,
     * the error message number, and the error message arguments encoded into
     * the URL hash.
     */ (message: string | number, args: string[]): string | undefined;
};
/**
 * Overrides the global "Error Message Handler" with a custom implementation.
 */
export declare function setErrorMessageHandler(handler: ErrorMessageHandler): void;
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