swr/dist/_internal/types.d.mts

React Hooks library for remote data fetching

import { SWRGlobalConfig } from '../index/index.mjs';
import * as revalidateEvents from './events.mjs';

/**
 * Global state tuple containing SWR's internal state management structures.
 *
 * This is the core state structure that manages all SWR operations internally.
 * Each element serves a specific purpose in the SWR ecosystem.
 *
 * @internal
 */
type GlobalState = [
    /** Event revalidators: Maps cache keys to arrays of revalidation callbacks */
    Record<string, RevalidateCallback[]>,
    /** Mutation timestamps: Maps cache keys to [start_timestamp, end_timestamp] tuples */
    Record<string, [number, number]>,
    /** Fetch cache: Maps cache keys to [data, timestamp] tuples */
    Record<string, [any, number]>,
    /** Preload cache: Maps cache keys to fetcher responses */
    Record<string, FetcherResponse<any>>,
    /** Scoped mutator function for cache updates */
    ScopedMutator,
    /** Cache setter function with prev/current value comparison */
    (key: string, value: any, prev: any) => void,
    /** Cache subscriber function that returns an unsubscribe function */
    (key: string, callback: (current: any, prev: any) => void) => () => void
];
/**
 * Response type that can be returned by fetcher functions.
 *
 * @template Data - The type of data returned by the fetcher
 * @public
 */
type FetcherResponse<Data = unknown> = Data | Promise<Data>;
/**
 * Basic fetcher function that accepts any arguments and returns data or a promise.
 *
 * This is the most permissive fetcher type, allowing any number of arguments
 * of any type. Used when type safety is not required or when dealing with
 * dynamic fetcher signatures.
 *
 * @template Data - The type of data returned by the fetcher
 * @param args - Variable arguments passed to the fetcher
 * @returns Data or a Promise that resolves to data
 * @public
 */
type BareFetcher<Data = unknown> = (...args: any[]) => FetcherResponse<Data>;
/**
 * Typed fetcher function that is constrained by the SWR key type.
 *
 * Provides type safety by ensuring the fetcher argument matches the key type.
 * The conditional type logic ensures that:
 * - If the key is a function returning a value, the fetcher receives that value
 * - If the key is falsy (null, undefined, false), the fetcher is never called
 * - Otherwise, the fetcher receives the key directly as its argument
 *
 * @template Data - The type of data returned by the fetcher
 * @template SWRKey - The type of the SWR key, used to infer fetcher arguments
 * @public
 */
type Fetcher<Data = unknown, SWRKey extends Key = Key> = SWRKey extends () => infer Arg | null | undefined | false ? (arg: Arg) => FetcherResponse<Data> : SWRKey extends null | undefined | false ? never : SWRKey extends infer Arg ? (arg: Arg) => FetcherResponse<Data> : never;
/**
 * Determines if data should block rendering based on suspense configuration.
 *
 * This conditional type is used internally to determine the return type of `data`
 * in SWRResponse. When suspense is enabled or fallbackData is provided, data
 * will never be undefined, allowing for non-nullable return types.
 *
 * The type resolution follows this logic:
 * 1. If global suspense is enabled → `true` (data never undefined)
 * 2. If no options provided → `false` (data can be undefined)
 * 3. If suspense is enabled in options → `true` (data never undefined)
 * 4. If fallbackData is provided → `true` (data never undefined)
 * 5. Otherwise → `false` (data can be undefined)
 *
 * @template Data - The data type
 * @template Options - The SWR configuration options
 * @returns `true` if data is guaranteed to be defined, `false` if it can be undefined
 * @internal
 */
type BlockingData<Data = any, Options = SWRDefaultOptions<Data>> = SWRGlobalConfig extends {
    suspense: true;
} ? true : Options extends undefined ? false : Options extends {
    suspense: true;
} ? true : Options extends {
    fallbackData: Data | Promise<Data>;
} ? true : false;
/**
 * Configuration types that are only used internally, not exposed to the user.
 *
 * These options are managed internally by SWR and passed between internal
 * functions. They are not part of the public API and should not be used
 * directly by consumers.
 *
 * @internal
 */
interface InternalConfiguration {
    /** The cache instance used to store SWR data and state */
    cache: Cache;
    /** Scoped mutator function for updating cache entries */
    mutate: ScopedMutator;
}
/**
 * Public configuration options for SWR.
 *
 * This interface defines all the configuration options that users can pass
 * to customize SWR's behavior. These options can be provided globally via
 * SWRConfig or per-hook via the config parameter.
 *
 * @template Data - The type of data returned by the fetcher
 * @template Error - The type of error that can be thrown
 * @template Fn - The fetcher function type
 *
 * @public
 * @see {@link https://swr.vercel.app/docs/options | SWR Options Documentation}
 */
interface PublicConfiguration<Data = any, Error = any, Fn extends Fetcher = BareFetcher> {
    /**
     *  error retry interval in milliseconds
     *  @defaultValue 5000
     */
    errorRetryInterval: number;
    /** max error retry count */
    errorRetryCount?: number;
    /**
     * timeout to trigger the onLoadingSlow event in milliseconds
     * @defaultValue 3000
     */
    loadingTimeout: number;
    /**
     * only revalidate once during a time span in milliseconds
     * @defaultValue 5000
     */
    focusThrottleInterval: number;
    /**
     * dedupe requests with the same key in this time span in milliseconds
     * @defaultValue 2000
     */
    dedupingInterval: number;
    /**
     *  * Disabled by default: `refreshInterval = 0`
     *  * If set to a number, polling interval in milliseconds
     *  * If set to a function, the function will receive the latest data and should return the interval in milliseconds
     *  @see {@link https://swr.vercel.app/docs/revalidation}
     */
    refreshInterval?: number | ((latestData: Data | undefined) => number);
    /**
     * polling when the window is invisible (if `refreshInterval` is enabled)
     * @defaultValue false
     */
    refreshWhenHidden?: boolean;
    /**
     * polling when the browser is offline (determined by `navigator.onLine`)
     *
     * When enabled, SWR will continue polling even when the browser is offline.
     * This can be useful for applications that need to check for connectivity
     * or cache updates while offline.
     *
     * @defaultValue false
     */
    refreshWhenOffline?: boolean;
    /**
     * automatically revalidate when window gets focused
     *
     * When enabled, SWR will automatically revalidate data when the user
     * returns focus to the window/tab. This ensures data freshness when
     * users switch between applications.
     *
     * @defaultValue true
     * @see {@link https://swr.vercel.app/docs/revalidation | Revalidation Documentation}
     */
    revalidateOnFocus: boolean;
    /**
     * automatically revalidate when the browser regains a network connection (via `navigator.onLine`)
     *
     * When enabled, SWR will automatically revalidate data when the browser
     * goes from offline to online state, ensuring data is up-to-date when
     * connectivity is restored.
     *
     * @defaultValue true
     * @see {@link https://swr.vercel.app/docs/revalidation | Revalidation Documentation}
     */
    revalidateOnReconnect: boolean;
    /**
     * enable or disable automatic revalidation when component is mounted
     *
     * Controls whether SWR should automatically fetch data when the component
     * mounts. When `undefined`, the behavior depends on `revalidateIfStale`.
     *
     * @defaultValue undefined (inherits from revalidateIfStale)
     */
    revalidateOnMount?: boolean;
    /**
     * automatically revalidate even if there is stale data
     * @defaultValue true
     * @see {@link https://swr.vercel.app/docs/revalidation#disable-automatic-revalidations}
     */
    revalidateIfStale: boolean;
    /**
     * retry when fetcher has an error
     * @defaultValue true
     */
    shouldRetryOnError: boolean | ((err: Error) => boolean);
    /**
     * keep the previous result when key is changed but data is not ready
     * @defaultValue false
     */
    keepPreviousData?: boolean;
    /**
     * @experimental  enable React Suspense mode
     * @defaultValue false
     * @see {@link https://swr.vercel.app/docs/suspense}
     */
    suspense?: boolean;
    /**
     * initial data to be returned (note: ***This is per-hook***)
     * @see {@link https://swr.vercel.app/docs/with-nextjs}
     */
    fallbackData?: Data | Promise<Data>;
    /**
     * warns when preload data is missing for a given key, this includes fallback
     * data, preload calls, or initial data from the cache provider
     * @defaultValue false
     */
    strictServerPrefetchWarning?: boolean;
    /**
     * the fetcher function
     */
    fetcher?: Fn;
    /**
     * array of middleware functions
     * @see {@link https://swr.vercel.app/docs/middleware}
     */
    use?: Middleware[];
    /**
     * a key-value object of multiple fallback data
     * @see {@link https://swr.vercel.app/docs/with-nextjs#pre-rendering-with-default-data}
     */
    fallback: {
        [key: string]: any;
    };
    /**
     * Function to detect whether pause revalidations, will ignore fetched data and errors when it returns true. Returns false by default.
     */
    isPaused: () => boolean;
    /**
     * callback function when a request takes too long to load (see `loadingTimeout`)
     */
    onLoadingSlow: (key: string, config: Readonly<PublicConfiguration<Data, Error, Fn>>) => void;
    /**
     * callback function when a request finishes successfully
     */
    onSuccess: (data: Data, key: string, config: Readonly<PublicConfiguration<Data, Error, Fn>>) => void;
    /**
     * callback function when a request returns an error
     */
    onError: (err: Error, key: string, config: Readonly<PublicConfiguration<Data, Error, Fn>>) => void;
    /**
     * handler for error retry
     */
    onErrorRetry: (err: Error, key: string, config: Readonly<PublicConfiguration<Data, Error, Fn>>, revalidate: Revalidator, revalidateOpts: Required<RevalidatorOptions>) => void;
    /**
     * callback function when a request is ignored due to race conditions
     */
    onDiscarded: (key: string) => void;
    /**
     * Comparison function used to detect when returned data has changed, to avoid spurious rerenders. By default, [dequal](https://github.com/lukeed/dequal) is used.
     */
    compare: (a: Data | undefined, b: Data | undefined) => boolean;
    /**
     * IsOnline and isVisible are functions that return a boolean, to determine if the application is "active". By default, SWR will bail out a revalidation if these conditions are not met.
     * @see {@link https://swr.vercel.app/docs/advanced/react-native#customize-focus-and-reconnect-events}
     */
    isOnline: () => boolean;
    /**
     * IsOnline and isVisible are functions that return a boolean, to determine if the application is "active". By default, SWR will bail out a revalidation if these conditions are not met.
     * @see {@link https://swr.vercel.app/docs/advanced/react-native#customize-focus-and-reconnect-events}
     */
    isVisible: () => boolean;
}
type FullConfiguration<Data = any, Error = any, Fn extends Fetcher = BareFetcher> = InternalConfiguration & PublicConfiguration<Data, Error, Fn>;
/**
 * Provider configuration for custom focus and reconnect event handling.
 *
 * This configuration allows custom implementations for detecting window focus
 * and network reconnection events. Useful for React Native or other environments
 * where the default browser APIs are not available.
 *
 * @public
 * @see {@link https://swr.vercel.app/docs/advanced/react-native | React Native Documentation}
 */
type ProviderConfiguration = {
    /**
     * Initialize focus event listener.
     *
     * @param callback - Function to call when window gains focus
     * @returns Optional cleanup function to remove the listener
     */
    initFocus: (callback: () => void) => (() => void) | void;
    /**
     * Initialize reconnect event listener.
     *
     * @param callback - Function to call when network reconnects
     * @returns Optional cleanup function to remove the listener
     */
    initReconnect: (callback: () => void) => (() => void) | void;
};
/**
 * The main useSWR hook interface with multiple overloads for different usage patterns.
 *
 * This interface provides type-safe overloads for various ways to call useSWR,
 * from simple key-only calls to complex configurations with custom fetchers.
 * The overloads ensure proper type inference for data, error, and configuration.
 *
 * @public
 *
 * @example Basic usage
 * ```ts
 * const { data, error } = useSWR('/api/data', fetcher)
 * ```
 *
 * @example With configuration
 * ```ts
 * const { data, error } = useSWR('/api/data', fetcher, {
 *   refreshInterval: 1000,
 *   revalidateOnFocus: false
 * })
 * ```
 *
 * @example Conditional fetching
 * ```ts
 * const { data, error } = useSWR(
 *   user.id ? `/api/user/${user.id}` : null,
 *   fetcher
 * )
 * ```
 *
 * @example Dynamic key with function
 * ```ts
 * const { data, error } = useSWR(
 *   () => user.id ? [`/api/user/${user.id}`, user.token] : null,
 *   ([url, token]) => fetcher(url, { headers: { Authorization: token } })
 * )
 * ```
 */
interface SWRHook {
    /**
     * Basic usage with just a key. Requires a global fetcher to be configured,
     * or can be used for client-side state management without fetching.
     *
     * @example
     * ```ts
     * // With global fetcher
     * const { data } = useSWR('/api/user')
     *
     * // Client state management
     * const { data, mutate } = useSWR('user-settings')
     * mutate({ theme: 'dark' })
     * ```
     */
    <Data = any, Error = any, SWRKey extends Key = StrictKey>(key: SWRKey): SWRResponse<Data, Error>;
    /**
     * Most common usage pattern with key and explicit fetcher function.
     * The fetcher receives the key as its argument and returns the data.
     *
     * @example
     * ```ts
     * const { data, error } = useSWR('/api/user/123',
     *   (url) => fetch(url).then(res => res.json())
     * )
     * ```
     */
    <Data = any, Error = any, SWRKey extends Key = StrictKey>(key: SWRKey, fetcher: Fetcher<Data, SWRKey> | null): SWRResponse<Data, Error>;
    /**
     * Key with fetcher using relaxed key constraints for dynamic or complex keys.
     * Allows more flexible key types including functions and objects.
     *
     * @example
     * ```ts
     * const { data } = useSWR(
     *   () => user ? ['/api/posts', user.id] : null,
     *   ([url, userId]) => fetchUserPosts(url, userId)
     * )
     * ```
     */
    <Data = any, Error = any, SWRKey extends Key = Key>(key: SWRKey, fetcher: Fetcher<Data, SWRKey> | null): SWRResponse<Data, Error>;
    /**
     * Key-only with advanced configuration options and strict typing.
     * Useful when you need specific SWR options but rely on a global fetcher.
     *
     * @example
     * ```ts
     * const { data } = useSWR<User>('/api/user', {
     *   refreshInterval: 5000,
     *   revalidateOnFocus: false
     * })
     * ```
     */
    <Data = any, Error = any, SWRKey extends Key = StrictKey, SWROptions extends SWRConfiguration<Data, Error, Fetcher<Data, SWRKey>> | undefined = SWRConfiguration<Data, Error, Fetcher<Data, SWRKey>> | undefined>(key: SWRKey): SWRResponse<Data, Error, SWROptions>;
    /**
     * Key with fetcher and advanced configuration options with strict typing.
     * Provides full control over fetching behavior and SWR options.
     *
     * @example
     * ```ts
     * const { data } = useSWR('/api/data', fetcher, {
     *   suspense: true,
     *   fallbackData: initialData
     * })
     * ```
     */
    <Data = any, Error = any, SWRKey extends Key = StrictKey, SWROptions extends SWRConfiguration<Data, Error, Fetcher<Data, SWRKey>> | undefined = SWRConfiguration<Data, Error, Fetcher<Data, SWRKey>> | undefined>(key: SWRKey, fetcher: Fetcher<Data, SWRKey> | null): SWRResponse<Data, Error, SWROptions>;
    /**
     * Key with configuration object but no explicit fetcher. Uses global fetcher
     * or can be used for pure client state management with configuration.
     *
     * @example
     * ```ts
     * // With global fetcher and config
     * const { data } = useSWR('/api/user', {
     *   refreshInterval: 1000
     * })
     *
     * // Client state with config
     * const { data } = useSWR('local-state', {
     *   fallbackData: defaultValue
     * })
     * ```
     */
    <Data = any, Error = any, SWRKey extends Key = StrictKey, SWROptions extends SWRConfiguration<Data, Error, Fetcher<Data, SWRKey>> | undefined = SWRConfiguration<Data, Error, Fetcher<Data, SWRKey>> | undefined>(key: SWRKey, config: SWRConfigurationWithOptionalFallback<SWROptions>): SWRResponse<Data, Error, SWROptions>;
    /**
     * Complete signature with key, fetcher, and configuration options.
     * Provides maximum flexibility and control over all SWR behavior.
     *
     * @example
     * ```ts
     * const { data, error, isLoading } = useSWR(
     *   '/api/user',
     *   async (url) => {
     *     const res = await fetch(url)
     *     if (!res.ok) throw new Error('Failed to fetch')
     *     return res.json()
     *   },
     *   {
     *     refreshInterval: 5000,
     *     onError: (error) => console.error('SWR Error:', error),
     *     fallbackData: { name: 'Loading...' }
     *   }
     * )
     * ```
     */
    <Data = any, Error = any, SWRKey extends Key = StrictKey, SWROptions extends SWRConfiguration<Data, Error, Fetcher<Data, SWRKey>> | undefined = SWRConfiguration<Data, Error, Fetcher<Data, SWRKey>> | undefined>(key: SWRKey, fetcher: Fetcher<Data, SWRKey> | null, config: SWRConfigurationWithOptionalFallback<SWROptions>): SWRResponse<Data, Error, SWROptions>;
    /**
     * Simple key-only usage with flexible key types. Most permissive overload
     * that accepts any valid key format.
     *
     * @example
     * ```ts
     * const { data } = useSWR('/api/data')
     * const { data: userData } = useSWR(['user', userId])
     * const { data: settings } = useSWR({ endpoint: '/settings', version: 'v1' })
     * ```
     */
    <Data = any, Error = any>(key: Key): SWRResponse<Data, Error>;
    /**
     * Key-only with configuration options using bare fetcher constraints.
     * Suitable for cases where fetcher type safety is less important.
     *
     * @example
     * ```ts
     * const { data } = useSWR('/api/data', {
     *   dedupingInterval: 5000
     * })
     * ```
     */
    <Data = any, Error = any, SWROptions extends SWRConfiguration<Data, Error, BareFetcher<Data>> | undefined = SWRConfiguration<Data, Error, BareFetcher<Data>> | undefined>(key: Key): SWRResponse<Data, Error, SWROptions>;
    /**
     * Key with bare fetcher function that accepts any arguments.
     * Provides less type safety but maximum flexibility for fetcher signatures.
     *
     * @example
     * ```ts
     * const { data } = useSWR('/api/user',
     *   (...args) => customFetcher(...args)
     * )
     * ```
     */
    <Data = any, Error = any, SWROptions extends SWRConfiguration<Data, Error, BareFetcher<Data>> | undefined = SWRConfiguration<Data, Error, BareFetcher<Data>> | undefined>(key: Key, fetcher: BareFetcher<Data> | null): SWRResponse<Data, Error, SWROptions>;
    /**
     * Key with configuration using relaxed fetcher typing constraints.
     * Useful when working with dynamic or loosely-typed fetcher functions.
     *
     * @example
     * ```ts
     * const { data } = useSWR(dynamicKey, {
     *   fetcher: customFetcher,
     *   refreshInterval: 2000
     * })
     * ```
     */
    <Data = any, Error = any, SWROptions extends SWRConfiguration<Data, Error, BareFetcher<Data>> | undefined = SWRConfiguration<Data, Error, BareFetcher<Data>> | undefined>(key: Key, config: SWRConfigurationWithOptionalFallback<SWROptions>): SWRResponse<Data, Error, SWROptions>;
    /**
     * Complete signature with key, bare fetcher, and configuration.
     * Most flexible overload with minimal type constraints, suitable for
     * complex scenarios where strict typing isn't feasible.
     *
     * @example
     * ```ts
     * const { data } = useSWR(
     *   complexKey,
     *   (...args) => legacyFetcher(...args),
     *   {
     *     refreshInterval: 10000,
     *     errorRetryCount: 3
     *   }
     * )
     * ```
     */
    <Data = any, Error = any, SWROptions extends SWRConfiguration<Data, Error, BareFetcher<Data>> | undefined = SWRConfiguration<Data, Error, BareFetcher<Data>> | undefined>(key: Key, fetcher: BareFetcher<Data> | null, config: SWRConfigurationWithOptionalFallback<SWROptions>): SWRResponse<Data, Error, SWROptions>;
}
/**
 * Middleware function type for extending SWR functionality.
 *
 * Middleware functions receive the next SWR hook in the chain and return
 * a modified hook function. This allows for composition of multiple
 * middleware functions to add features like logging, caching, or
 * request/response transformation.
 *
 * The middleware guarantees that a SWRHook receives a key, fetcher,
 * and config as arguments, providing a consistent interface for
 * middleware authors.
 *
 * @param useSWRNext - The next SWR hook function in the middleware chain
 * @returns A new SWR hook function with middleware functionality applied
 *
 * @template Data - The type of data returned by the fetcher
 * @template Error - The type of error that can be thrown
 *
 * @public
 * @see {@link https://swr.vercel.app/docs/middleware | Middleware Documentation}
 *
 * @example
 * ```ts
 * const logger: Middleware = (useSWRNext) => (key, fetcher, config) => {
 *   console.log('SWR Request:', key)
 *   return useSWRNext(key, fetcher, config)
 * }
 * ```
 */
type Middleware = (useSWRNext: SWRHook) => <Data = any, Error = any>(key: Key, fetcher: BareFetcher<Data> | null, config: SWRConfiguration<Data, Error, BareFetcher<Data>>) => SWRResponse<Data, Error>;
/**
 * Represents a tuple of arguments that can be passed to a fetcher.
 *
 * The first element is typically the primary key (like a URL), followed
 * by additional parameters that affect the request (like query parameters,
 * headers, or request options).
 *
 */
type ArgumentsTuple = readonly [any, ...unknown[]];
/**
 * Valid types for SWR keys.
 *
 * SWR keys identify unique requests and can be:
 * - `string`: Simple URL or identifier
 * - `ArgumentsTuple`: Array with URL and additional parameters
 * - `Record<any, any>`: Object that will be serialized
 * - `null | undefined | false`: Falsy values disable the request
 *
 * When a key is falsy, SWR will not make the request, allowing for
 * conditional fetching based on application state.
 *
 * @public
 *
 * @example
 * ```ts
 * // String key
 * useSWR('/api/users', fetcher)
 *
 * // Array key with parameters
 * useSWR(['/api/user', userId], ([url, id]) => fetcher(`${url}/${id}`))
 *
 * // Object key
 * useSWR({ url: '/api/data', params: { page: 1 } }, fetcher)
 *
 * // Conditional key
 * useSWR(userId ? `/api/user/${userId}` : null, fetcher)
 * ```
 */
type Arguments = string | ArgumentsTuple | Record<any, any> | null | undefined | false;
/**
 * SWR key that can be static or a function that returns arguments.
 *
 * When a function is provided, it's called on each render to determine
 * the current key. This allows for dynamic keys based on component state
 * or props.
 *
 * @public
 *
 * @example
 * ```ts
 * // Static key
 * useSWR('/api/data', fetcher)
 *
 * // Dynamic key function
 * useSWR(() => user ? `/api/user/${user.id}` : null, fetcher)
 * ```
 */
type Key = Arguments | (() => Arguments);
/**
 * Strict tuple key type that only allows tuples or falsy values.
 *
 * @internal
 */
type StrictTupleKey = ArgumentsTuple | null | undefined | false;
/**
 * Strict key type for internal use.
 *
 * @internal
 */
type StrictKey = StrictTupleKey | (() => StrictTupleKey);
/**
 * Callback function type for mutator operations.
 *
 * This function receives the current cached data and can return new data
 * to update the cache. It can be synchronous or asynchronous, and can
 * return undefined to indicate no change should be made.
 *
 * @template Data - The type of the cached data
 * @param currentData - The current data in the cache (may be undefined)
 * @returns New data to set, undefined for no change, or a Promise resolving to either
 *
 * @public
 *
 * @example
 * ```ts
 * // Increment a counter
 * mutate(key, (current: number = 0) => current + 1)
 *
 * // Async update
 * mutate(key, async (current) => {
 *   const updated = await updateData(current)
 *   return updated
 * })
 * ```
 */
type MutatorCallback<Data = any> = (currentData?: Data) => Promise<undefined | Data> | undefined | Data;
/**
 * Options for configuring mutator behavior.
 *
 * These options control how the mutation affects the cache, revalidation,
 * and error handling behavior.
 *
 * @template Data - The type of the data related to the key
 * @template MutationData - The type of the data returned by the mutator
 *
 * @public
 */
type MutatorOptions<Data = any, MutationData = Data> = {
    /**
     * Whether to revalidate the cache after mutation.
     *
     * Can be a boolean or a function that receives the new data and key
     * to determine whether revalidation should occur.
     *
     * @defaultValue true
     */
    revalidate?: boolean | ((data: Data, key: Arguments) => boolean);
    /**
     * Whether and how to populate the cache with mutation results.
     *
     * - `false`: Don't update the cache
     * - `true`: Update cache with mutation result directly
     * - Function: Transform mutation result before caching
     *
     * @defaultValue true
     */
    populateCache?: boolean | ((result: MutationData, currentData: Data | undefined) => Data);
    /**
     * Optimistic data to show immediately while mutation is pending.
     *
     * Can be the data directly or a function that computes it based on
     * current and displayed data. Useful for immediate UI feedback.
     *
     * @defaultValue undefined
     */
    optimisticData?: Data | ((currentData: Data | undefined, displayedData: Data | undefined) => Data);
    /**
     * Whether to rollback optimistic updates on error.
     *
     * Can be a boolean or a function that receives the error to determine
     * whether rollback should occur.
     *
     * @defaultValue true
     */
    rollbackOnError?: boolean | ((error: unknown) => boolean);
    /**
     * Whether to throw errors instead of returning them in the error field.
     *
     * When true, errors will be thrown and can be caught with try/catch.
     * When false, errors are returned in the response object.
     *
     * @defaultValue false
     */
    throwOnError?: boolean;
};
type MutatorConfig = {
    revalidate?: boolean;
    populateCache?: boolean;
};
type Broadcaster<Data = any, Error = any> = (cache: Cache<Data>, key: string, data: Data, error?: Error, isValidating?: boolean, revalidate?: boolean, populateCache?: boolean) => Promise<Data>;
/**
 * Internal state structure stored in the cache.
 *
 * This represents the complete state for a cache entry, including
 * data, error, and loading states. All fields are optional as they
 * may not be present depending on the request lifecycle.
 *
 * @template Data - The type of data stored
 * @template Error - The type of error that can occur
 *
 * @internal
 */
type State<Data = any, Error = any> = {
    /** The cached data, if available */
    data?: Data;
    /** The error object, if an error occurred */
    error?: Error;
    /** Whether a revalidation is currently in progress */
    isValidating?: boolean;
    /** Whether this is the initial load with no cached data */
    isLoading?: boolean;
};
type MutatorFn<Data = any> = (cache: Cache, key: Key, data?: Data | Promise<Data> | MutatorCallback<Data>, opts?: boolean | MutatorOptions<Data>) => Promise<Data | undefined>;
type MutatorWrapper<Fn> = Fn extends (...args: [...infer Parameters]) => infer Result ? Parameters[3] extends boolean ? Result : Parameters[3] extends Required<Pick<MutatorOptions, 'populateCache'>> ? Parameters[3]['populateCache'] extends false ? never : Result : Result : never;
type Mutator<Data = any> = MutatorWrapper<MutatorFn<Data>>;
interface ScopedMutator {
    /**
     * @typeParam Data - The type of the data related to the key
     * @typeParam MutationData - The type of the data returned by the mutator
     */
    <Data = any, MutationData = Data>(matcher: (key?: Arguments) => boolean, data?: MutationData | Promise<MutationData> | MutatorCallback<MutationData>, opts?: boolean | MutatorOptions<Data, MutationData>): Promise<Array<MutationData | undefined>>;
    /**
     * @typeParam Data - The type of the data related to the key
     * @typeParam MutationData - The type of the data returned by the mutator
     */
    <Data = any, T = Data>(key: Arguments, data?: T | Promise<T> | MutatorCallback<T>, opts?: boolean | MutatorOptions<Data, T>): Promise<T | undefined>;
}
/**
 * @typeParam Data - The type of the data related to the key
 * @typeParam MutationData - The type of the data returned by the mutator
 */
type KeyedMutator<Data> = <MutationData = Data>(data?: Data | Promise<Data | undefined> | MutatorCallback<Data>, opts?: boolean | MutatorOptions<Data, MutationData>) => Promise<Data | MutationData | undefined>;
type SWRConfiguration<Data = any, Error = any, Fn extends BareFetcher<any> = BareFetcher<any>> = Partial<PublicConfiguration<Data, Error, Fn>> & Partial<ProviderConfiguration> & {
    provider?: (cache: Readonly<Cache>) => Cache;
};
type IsLoadingResponse<Data = any, Options = SWRDefaultOptions<Data>> = SWRGlobalConfig extends {
    suspense: true;
} ? Options extends {
    suspense: true;
} ? false : false : boolean;
type SWRDefaultOptions<Data> = SWRConfiguration<Data, Error, Fetcher<Data, Key>>;
type SWRConfigurationWithOptionalFallback<Options> = Options extends SWRConfiguration & Required<Pick<SWRConfiguration, 'fallbackData'>> ? Omit<Options, 'fallbackData'> & Pick<Partial<Options>, 'fallbackData'> : Options;
/**
 * The response object returned by SWR hooks.
 *
 * This interface represents the return value of useSWR and related hooks,
 * providing access to data, error state, and control functions.
 *
 * @template Data - The type of data returned by the fetcher
 * @template Error - The type of error that can be thrown
 * @template Config - The configuration type used to determine blocking behavior
 *
 * @public
 */
interface SWRResponse<Data = any, Error = any, Config = any> {
    /**
     * The data returned by the fetcher function.
     *
     * - When suspense is enabled or fallbackData is provided: always defined
     * - Otherwise: `undefined` during initial load or when key is falsy
     */
    data: BlockingData<Data, Config> extends true ? Data : Data | undefined;
    /**
     * The error object thrown by the fetcher function.
     *
     * `undefined` when there's no error or when a request is in progress.
     */
    error: Error | undefined;
    /**
     * Function to mutate the cached data for this specific key.
     *
     * This is a bound version of the global mutate function that automatically
     * uses the current key, providing type safety and convenience.
     */
    mutate: KeyedMutator<Data>;
    /**
     * Whether the request is currently being validated (loading fresh data).
     *
     * `true` during initial load, revalidation, or when mutate is called
     * with a promise or async function.
     */
    isValidating: boolean;
    /**
     * Whether the request is in initial loading state.
     *
     * `true` only during the initial load when there's no cached data.
     * Unlike `isValidating`, this becomes `false` once data is available.
     */
    isLoading: IsLoadingResponse<Data, Config>;
}
type KeyLoader<Args extends Arguments = Arguments> = ((index: number, previousPageData: any | null) => Args) | null;
interface RevalidatorOptions {
    retryCount?: number;
    dedupe?: boolean;
}
type Revalidator = (revalidateOpts?: RevalidatorOptions) => Promise<boolean> | void;
type RevalidateEvent = typeof revalidateEvents.FOCUS_EVENT | typeof revalidateEvents.RECONNECT_EVENT | typeof revalidateEvents.MUTATE_EVENT | typeof revalidateEvents.ERROR_REVALIDATE_EVENT;
type RevalidateCallbackReturnType = {
    [revalidateEvents.FOCUS_EVENT]: void;
    [revalidateEvents.RECONNECT_EVENT]: void;
    [revalidateEvents.MUTATE_EVENT]: Promise<boolean>;
    [revalidateEvents.ERROR_REVALIDATE_EVENT]: void;
};
type RevalidateCallback = <K extends RevalidateEvent>(type: K, opts?: any) => RevalidateCallbackReturnType[K];
/**
 * Cache interface for storing SWR state.
 *
 * This interface defines the contract for cache providers used by SWR.
 * The default implementation uses a Map, but custom cache providers
 * can implement this interface to provide different storage mechanisms.
 *
 * @template Data - The type of data stored in the cache
 *
 * @public
 * @see {@link https://swr.vercel.app/docs/advanced/cache | Cache Documentation}
 */
interface Cache<Data = any> {
    /**
     * Get an iterator of all cache keys.
     *
     * @returns Iterator that yields all cache keys as strings
     */
    keys(): IterableIterator<string>;
    /**
     * Get the cached state for a key.
     *
     * @param key - The cache key to look up
     * @returns The cached state or undefined if not found
     */
    get(key: string): State<Data> | undefined;
    /**
     * Set the cached state for a key.
     *
     * @param key - The cache key to set
     * @param value - The state to cache
     */
    set(key: string, value: State<Data>): void;
    /**
     * Delete a cached entry.
     *
     * @param key - The cache key to delete
     */
    delete(key: string): void;
}
interface StateDependencies {
    data?: boolean;
    error?: boolean;
    isValidating?: boolean;
    isLoading?: boolean;
}

export type { Arguments, BareFetcher, BlockingData, Broadcaster, Cache, Fetcher, FetcherResponse, FullConfiguration, GlobalState, InternalConfiguration, IsLoadingResponse, Key, KeyLoader, KeyedMutator, Middleware, Mutator, MutatorCallback, MutatorConfig, MutatorFn, MutatorOptions, MutatorWrapper, ProviderConfiguration, PublicConfiguration, RevalidateCallback, RevalidateEvent, Revalidator, RevalidatorOptions, SWRConfiguration, SWRHook, SWRResponse, ScopedMutator, State, StateDependencies, StrictTupleKey };