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import { isNotNullable } from './is-not-nullable.ts';
/**
* A resource that can be closed synchronously.
*
* Objects implementing this interface provide a `close()` method that performs cleanup operations immediately and
* returns `void`. This is typically used for resources that don't require asynchronous operations during cleanup, such
* as event listeners, timers, or simple state cleanup.
*
* The closable protocol expects that a single invocation of close is sufficient to perform all required operations
* (such as releasing resources), and that additional calls to close are safe and have no effect.
*/
export type SyncClosable = {
/**
* Performs synchronous cleanup operations, returning immediately after invoked.
*/
readonly close: () => void;
};
/**
* A resource that can be closed asynchronously.
*
* Objects implementing this interface provide a `close()` method that returns a `Promise<void>`. This is typically used
* for resources that require asynchronous operations during cleanup, such as file handles, database connections, or
* network resources.
*
* The closable protocol expects that a single invocation of close is sufficient to perform all required operations
* (such as releasing resources), and that additional calls to close are safe and have no effect.
*/
export type AsyncClosable = {
/**
* Performs asynchronous cleanup operations, returning a promise that resolves when the cleanup is complete.
*/
readonly close: () => Promise<void>;
};
/**
* A resource that can be closed either synchronously or asynchronously.
*
* This union type represents any closable resource, whether it requires synchronous or asynchronous cleanup. It's the
* most flexible type for accepting closable resources when the cleanup method is not known in advance.
*
* The closable protocol expects that a single invocation of close is sufficient to perform all required operations
* (such as releasing resources), and that additional calls to close are safe and have no effect.
*/
export type Closable = SyncClosable | AsyncClosable;
/**
* Closes all provided closables, returning a promise if at least one closable is asynchronous.
*
* This function ensures all closables are properly closed even if some throw errors during cleanup. Errors from
* individual closables are accumulated and then thrown (for synchronous closables) or rejected (for asynchronous
* closables) after all cleanup operations complete.
*
* The return type is automatically inferred based on the types of the provided closables:
*
* - All synchronous closables → returns `void`
* - Any asynchronous closables → returns `Promise<void>`
* - Ambiguous types → defaults to `Promise<void>` for safety
*
* @example Synchronous closables
*
* ```ts
* import { closeAll } from 'emitnlog/utils';
*
* const fileHandle = { close: () => console.log('File closed') };
* const eventListener = { close: () => console.log('Listener removed') };
*
* closeAll(fileHandle, eventListener); // Returns void immediately
* ```
*
* @example Mixed synchronous and asynchronous closables
*
* ```ts
* import { closeAll } from 'emitnlog/utils';
*
* const timer = { close: () => clearInterval(timerId) };
* const dbConnection = { close: async () => await db.disconnect() };
*
* await closeAll(timer, dbConnection); // Returns Promise<void>
* ```
*
* @example Error handling with single error
*
* ```ts
* import { closeAll } from 'emitnlog/utils';
*
* const failing = {
* close: () => {
* throw new Error('Cleanup failed');
* },
* };
* const working = { close: () => console.log('Cleaned up successfully') };
*
* try {
* closeAll(failing, working);
* } catch (error) {
* console.log(error.message); // 'Cleanup failed'
* // Both closables were called, but error was thrown after all completed
* }
* ```
*
* @example Error handling with multiple errors
*
* ```ts
* import { closeAll } from 'emitnlog/utils';
*
* const failing1 = {
* close: () => {
* throw new Error('First error');
* },
* };
* const failing2 = {
* close: async () => {
* throw new Error('Second error');
* },
* };
*
* try {
* await closeAll(failing1, failing2);
* } catch (error) {
* console.log(error.message); // 'Multiple errors occurred while closing closables'
* console.log(error.cause); // Array containing both Error objects
* }
* ```
*
* @param closables - The closables to close
* @returns `void` if all closables are synchronous, `Promise<void>` if any are asynchronous
* @throws {Error} Single error if only one closable fails, or aggregate error with `cause` array if multiple fail
*/
export const closeAll = <T extends readonly ClosableLike[]>(...closables: T): CloseAllReturn<T> => {
if (closables.length === 0) {
return undefined as CloseAllReturn<T>;
}
if (closables.length === 1) {
return closables[0].close?.() as CloseAllReturn<T>;
}
const errors: Error[] = [];
const onError = (index: number) => (error: unknown) => {
errors[index] = errorify(error);
};
const handleErrors = () => {
const prunedErrors = errors.filter(isNotNullable);
if (prunedErrors.length) {
if (prunedErrors.length === 1) {
throw prunedErrors[0];
}
throw new Error('Multiple errors occurred while closing closables', { cause: prunedErrors });
}
};
const promises: Promise<void>[] = closables
.map((closable, index): unknown => closable.close && asSafeClosable(closable as Closable, onError(index)).close())
.filter((result): result is Promise<void> => result instanceof Promise);
if (promises.length) {
return Promise.all(promises).then(() => {
handleErrors();
return undefined;
}) as CloseAllReturn<T>;
}
handleErrors();
return undefined as CloseAllReturn<T>;
};
/**
* Creates a single closable from one or more cleanup operations.
*
* This function serves two purposes:
*
* 1. It transforms individual cleanup functions (or objects with optional `close` methods) into proper closables.
* 2. It groups multiple such inputs into a single closable that performs all cleanup steps in order.
*
* All inputs are normalized to proper closables and closed when the returned `close()` is invoked. Errors are
* accumulated and handled using the same strategy as {@link closeAll}.
*
* The returned closable guarantees:
*
* - It can be called only once (subsequent calls are no-ops).
* - The return type of `close()` matches the most flexible input:
*
* - All synchronous inputs → returns `SyncClosable`
* - Any asynchronous input → returns `AsyncClosable`
* - Ambiguous → defaults to `AsyncClosable` for safety
*
* See {@link createCloser} for a more convenient way to create a "live closable" that can be used to accumulate
* closables as they are instantiated.
*
* @example Creating a closable from a single function
*
* ```ts
* import { asClosable } from 'emitnlog/utils';
*
* const timerCleanup = () => clearTimeout(timerId);
* const closable = asClosable(timerCleanup);
* closable.close(); // Runs the cleanup
* ```
*
* @example Combining multiple cleanup steps
*
* ```ts
* import { asClosable } from 'emitnlog/utils';
*
* const db = { close: async () => await disconnect() };
* const file = { close: () => console.log('Closed file') };
* const cleanup = () => console.log('Manual cleanup');
*
* const combined = asClosable(db, file, cleanup);
* await combined.close(); // Closes all in order
* ```
*
* @example Error handling
*
* ```ts
* import { asClosable } from 'emitnlog/utils';
*
* const failing = () => {
* throw new Error('Cleanup failed');
* };
* const working = () => console.log('Success');
*
* const combined = asClosable(failing, working);
*
* try {
* combined.close();
* } catch (error) {
* console.log(error.message); // 'Cleanup failed'
* // Both functions were called despite the error
* }
* ```
*
* @param input - One or more functions, closables, or partial closables to wrap
* @returns A closable that closes all specified inputs when `close()` is called
*/
export const asClosable = <T extends readonly ClosableLikeOrFunction[]>(...input: T): AsClosableReturn<T> => {
const closables: readonly Closable[] = input
.map((i): Closable | undefined => {
if (typeof i === 'function') {
const closable: Closable = {
close: () => {
const value = i();
if (value instanceof Promise) {
return value.then(() => undefined);
}
return undefined;
},
};
return closable;
}
if (!i.close) {
return undefined;
}
return i as Closable;
})
.filter(isNotNullable);
let closed = false;
const combined: Closable = {
close: () => {
if (closed) {
return undefined;
}
closed = true;
return closeAll(...closables);
},
};
return combined as AsClosableReturn<T>;
};
/**
* Wraps a closable to prevent errors during `close()` from propagating.
*
* This utility creates a "safe" version of a closable that catches both synchronous throws and asynchronous rejections
* during the close operation. If an error occurs, the optional `onError` callback is invoked with the error, and the
* error is then swallowed (the close operation completes normally).
*
* This is particularly useful for ensuring cleanup operations never fail, which is important in scenarios like
* application shutdown, resource cleanup chains, or when combining multiple closables with {@link asClosable} or
* {@link closeAll}.
*
* @example Basic usage
*
* ```ts
* import { asSafeClosable } from 'emitnlog/utils';
*
* const failing = {
* close: () => {
* throw new Error('Will be ignored');
* },
* };
* const silent = asSafeClosable(failing);
* silent.close(); // Error is silently swallowed
* ```
*
* @example Basic usage with error handling
*
* ```ts
* import { createConsoleLogLogger } from 'emitnlog/logger';
* import { asSafeClosable } from 'emitnlog/utils';
*
* const unreliableResource = {
* close: () => {
* throw new Error('Cleanup failed');
* },
* };
*
* const logger = createConsoleLogLogger();
* const safeResource = asSafeClosable(unreliableResource, (error) => {
* logger.w`Cleanup error: ${error}'`;
* });
*
* safeResource.close(); // Never throws, logs warning instead
* ```
*
* @example With asynchronous closables
*
* ```ts
* import { asSafeClosable } from 'emitnlog/utils';
*
* const asyncResource = {
* close: async () => {
* throw new Error('Async cleanup failed');
* },
* };
*
* const safeAsync = asSafeClosable(asyncResource, (error) => {
* console.error('Async cleanup error:', error);
* });
*
* await safeAsync.close(); // Never rejects, logs error instead
* ```
*
* @example Combining with asClosable for robust cleanup
*
* ```ts
* import { asClosable, asSafeClosable } from 'emitnlog/utils';
*
* const robustCleanup = asClosable(
* asSafeClosable(riskyResource1),
* asSafeClosable(riskyResource2),
* asSafeClosable(riskyResource3),
* );
*
* await robustCleanup.close(); // Guaranteed to not throw/reject
* ```
*
* @param closable - The closable to wrap with error protection
* @param onError - Optional callback invoked when an error occurs during close
* @returns A closable that never throws or rejects, matching the sync/async nature of the input
*/
export const asSafeClosable = <C extends Closable>(
closable: C,
onError?: (error: unknown) => void,
): IsElementAsync<C> extends true ? AsyncClosable : SyncClosable => {
let closed = false;
const safe = {
close: () => {
if (closed) {
return undefined;
}
closed = true;
try {
const value = closable.close();
if (value instanceof Promise) {
return value.catch((error: unknown) => {
try {
onError?.(error);
} catch {
// ignore
}
return undefined;
});
}
} catch (error) {
try {
onError?.(error);
} catch {
// ignore
}
}
return undefined;
},
};
return safe as IsElementAsync<C> extends true ? AsyncClosable : SyncClosable;
};
/**
* A container for managing multiple closables with a single `close()` call.
*
* This utility type represents a composite closable that accumulates other closables over time via the `add()` method.
* Once `close()` is called, all registered closables are closed in reverse order, and the internal collection is
* cleared. Any subsequent calls to `add()` are still allowed, but the already-closed closables will not be invoked
* again.
*
* Useful for ensuring cleanup logic is always executed, even in complex control flows with multiple return points.
*/
export type Closer = Closable & {
/**
* Adds a closable to be handled when the closer is closed.
*
* @param closable
* @returns The closable
*/
readonly add: <T extends ClosableLike>(closable: T) => T;
/**
* The number of closables that have not been closed.
*/
readonly size: number;
};
/**
* Creates a `Closer` that manages a group of closables as a single unit, simplifying resource management— especially in
* functions with multiple return points or error paths.
*
* The returned object allows you to register closables via `add()`, and later invoke `close()` once to clean them all
* up. Closables are executed in reverse order of registration (last in, first closed), which is useful when resources
* depend on each other.
*
* After `close()` is called:
*
* - The internal list is cleared, so previously added closables won't be called again.
* - Further `add()` calls are still allowed and track newly added closables.
* - A subsequent call to `close()` will only affect those new closables.
*
* Any errors thrown or rejected by the closables are accumulated and handled using the same strategy as
* {@link closeAll}.
*
* The difference between this utility and {@link asClosable} is that the object returned here is a "live closable" that
* can be used to accumulate closables as they are instantiated, whereas `asClosable` is meant to be a "one time"
* utility that produces a single closable. Additionally, `closer.add(...)` preserves and returns the original
* closable’s type, making it easier to work with typed resources.
*
* @example Basic usage
*
* ```ts
* import type { Logger } from 'emitnlog/logger';
* import { createConsoleByLevelLogger } from 'emitnlog/logger';
* import { asClosable, createCloser } from 'emitnlog/utils';
*
* const closer = createCloser();
*
* if (enableDB) {
* const db: DB = closer.add(asClosable(() => disconnect()));
* ...
* }
*
* const logger: Logger = closer.add(createConsoleByLevelLogger());
*
* // When needed...
* await closer.close(); // Closes logger first, then db
* ```
*
* @param input - Optional initial set of closables
* @returns A `Closer` that can register and close closables as a group
*/
export const createCloser = (...input: readonly Closable[]): Closer => {
const closables = new Set<ClosableLike>(input);
const closer: Closer = {
add: (closable) => {
closables.add(closable);
return closable;
},
get size() {
return closables.size;
},
close: () => {
if (!closables.size) {
return undefined;
}
const array = Array.from(closables).reverse();
closables.clear();
return closeAll(...array);
},
};
return closer;
};
type PartialSyncClosable = Partial<SyncClosable>;
type PartialAsyncClosable = Partial<AsyncClosable>;
type ClosableLike = SyncClosable | PartialSyncClosable | AsyncClosable | PartialAsyncClosable;
type ClosableLikeOrFunction = ClosableLike | (() => unknown);
type IsElementAsync<E> = E extends () => infer R
? R extends Promise<unknown>
? true
: false
: E extends { readonly close: () => infer R }
? R extends Promise<unknown>
? true
: false
: E extends { readonly close?: () => infer R }
? R extends Promise<unknown>
? true
: false
: false;
type IsArrayAsync<A extends readonly ClosableLikeOrFunction[]> = A extends [
infer F extends ClosableLikeOrFunction,
...infer R extends readonly ClosableLikeOrFunction[],
]
? IsElementAsync<F> extends false
? R extends []
? false
: IsArrayAsync<R>
: true
: A extends readonly (infer Item extends ClosableLikeOrFunction)[]
? IsElementAsync<Item> extends false
? false
: true
: false;
// eslint-disable-next-line @typescript-eslint/no-invalid-void-type
type CloseAllReturn<T extends readonly ClosableLike[]> = IsArrayAsync<T> extends true ? Promise<void> : void;
type AsClosableReturn<T extends readonly ClosableLikeOrFunction[]> =
IsArrayAsync<T> extends true ? AsyncClosable : SyncClosable;
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