/**
 * Which release's defaults apply where an option is left out: 3.0's, or 2.x's. 3.0 turns on three
 * settings that 2.x kept opt-in; `2.x` keeps all three off at once, so an application can upgrade first
 * and turn them on when it is ready. An option set explicitly always wins, under either.
 */
/** A release whose defaults apply: `3.0`, the default, or `2.x`, which keeps 2.x's three settings off. */
export type NexusDefaults = '2.x' | '3.0';
/** One default that 3.0 changes: what it is, what 2.x does, what 3.0 does, and what to do first. */
export interface DefaultChange {
    /** The setting, as its option is named. */
    setting: string;
    /** Where it is set. */
    module: string;
    /** What 2.x did when the option is left out, as `useDefaults('2.x')` still does. */
    today: string;
    /** What 3.0 does when it is left out. */
    next: string;
    /** What to do before turning it on, if anything. */
    before: string;
}
/** The defaults 3.0 changes, each kept as 2.x had it by `useDefaults('2.x')`. */
export declare const DEFAULT_CHANGES: readonly DefaultChange[];
/**
 * Chooses which release's defaults apply to everything created after it: `3.0`, the default, or `2.x`,
 * which keeps the three settings 3.0 turns on off, for an application that upgrades before it turns them
 * on. Call it before creating a tracer, an operation store, or a deployment: each reads the defaults when
 * it is created. Overrides `NEXUS_DEFAULTS`.
 */
export declare function useDefaults(release: NexusDefaults): void;
/**
 * The defaults in effect: as `useDefaults()` chose, else the `NEXUS_DEFAULTS` environment variable,
 * `2.x` or `3.0`, else `3.0`. Throws for any other value of the variable, rather than ignore a typo.
 */
export declare function nexusDefaults(): NexusDefaults;