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prevent passing a specific error type for .fromThrowable without providing an error mapping function #583

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prevent passing a specific error type for .fromThrowable without providing an error mapping function #583

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eada607
make fromThrowable type more strict
boyeln Sep 12, 2024
6736079
add changeset
boyeln Sep 12, 2024
77c430f
Merge branch 'master' into master
supermacro Nov 10, 2024
366dbed
Merge branch 'master' into master
m-shaka Mar 8, 2025
695a160
Merge branch 'master' into master
boyeln Mar 11, 2025
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5 changes: 5 additions & 0 deletions .changeset/grumpy-hats-unite.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
'neverthrow': minor
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This might be considered a breaking change, since users that use the function like described in the PR will get red squiggles. However, I would argue that this is a "type bug", and shouldn't be considered a valid use case

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I'd agree to consider this a bug fix

---

prevent passing a specific error type for `.fromThrowable` without providing an error mapping function
13 changes: 11 additions & 2 deletions src/result-async.ts
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Expand Up @@ -42,17 +42,26 @@ export class ResultAsync<T, E> implements PromiseLike<Result<T, E>> {
return new ResultAsync(newPromise)
}

// eslint-disable-next-line @typescript-eslint/no-explicit-any
static fromThrowable<A extends readonly any[], R>(
fn: (...args: A) => Promise<R>,
): (...args: A) => ResultAsync<R, unknown>
// eslint-disable-next-line @typescript-eslint/no-explicit-any
static fromThrowable<A extends readonly any[], R, E>(
fn: (...args: A) => Promise<R>,
errorFn: (err: unknown) => E,
): (...args: A) => ResultAsync<R, E>
// eslint-disable-next-line @typescript-eslint/no-explicit-any
static fromThrowable<A extends readonly any[], R, E>(
fn: (...args: A) => Promise<R>,
errorFn?: (err: unknown) => E,
): (...args: A) => ResultAsync<R, E> {
): (...args: A) => ResultAsync<R, E | unknown> {
return (...args) => {
return new ResultAsync(
(async () => {
try {
return new Ok(await fn(...args))
} catch (error) {
} catch (error: unknown) {
return new Err(errorFn ? errorFn(error) : error)
}
})(),
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21 changes: 18 additions & 3 deletions src/result.ts
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Expand Up @@ -17,18 +17,33 @@ export namespace Result {
* arguments but returning `Ok` if successful, `Err` if the function throws
*
* @param fn function to wrap with ok on success or err on failure
* @param errorFn when an error is thrown, this will wrap the error result if provided
*/
// eslint-disable-next-line @typescript-eslint/no-explicit-any
export function fromThrowable<Fn extends (...args: readonly any[]) => any>(
fn: Fn,
): (...args: Parameters<Fn>) => Result<ReturnType<Fn>, unknown>
/**
* Wraps a function with a try catch, creating a new function with the same
* arguments but returning `Ok` if successful, `Err` if the function throws
*
* @param fn function to wrap with ok on success or err on failure
* @param errorFn when an error is thrown, this will wrap the error result
*/
Comment on lines +25 to +31
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It's not the most elegant to have to maintain two versions of the documentation, however I'm not aware of any other way of doing it. Please let me know if there's a better way!

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You can't avoid that, I guess.
Here is the official doc comment of Array.prorotype.concat. The same content is written in two places.
image

// eslint-disable-next-line @typescript-eslint/no-explicit-any
export function fromThrowable<Fn extends (...args: readonly any[]) => any, E>(
fn: Fn,
errorFn: (e: unknown) => E,
): (...args: Parameters<Fn>) => Result<ReturnType<Fn>, E>
// eslint-disable-next-line @typescript-eslint/no-explicit-any
export function fromThrowable<Fn extends (...args: readonly any[]) => any, E>(
fn: Fn,
errorFn?: (e: unknown) => E,
): (...args: Parameters<Fn>) => Result<ReturnType<Fn>, E> {
): (...args: Parameters<Fn>) => Result<ReturnType<Fn>, E | unknown> {
return (...args) => {
try {
const result = fn(...args)
return ok(result)
} catch (e) {
} catch (e: unknown) {
return err(errorFn ? errorFn(e) : e)
}
}
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