<Input>(): <
const Tag extends Tags<Input>,
const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>
>(
tag: Tag,
reasonTag: ReasonTag
) => Filter<
Input,
ExtractReason<ExtractTag<Input, Tag>, ReasonTag>,
Input
>
<
Input,
const Tag extends Tags<Input>,
const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>
>(
tag: Tag,
reasonTag: ReasonTag
): Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>
<const Tag extends string, const ReasonTag extends string>(
tag: Tag,
reasonTag: ReasonTag
): <Input>(
input: Input
) => Result.Result<
ExtractReason<ExtractTag<Input, Tag>, ReasonTag>,
Input
>Creates a filter that extracts a reason from a tagged error.
constructors
Source effect/Filter.ts:49416 lines
export const const reason: {
<Input>(): <
Tag extends Tags<Input>,
ReasonTag extends ReasonTags<
ExtractTag<Input, Tag>
>
>(
tag: Tag,
reasonTag: ReasonTag
) => Filter<
Input,
ExtractReason<
ExtractTag<Input, Tag>,
ReasonTag
>,
Input
>
<
Input,
Tag extends Tags<Input>,
ReasonTag extends ReasonTags<
ExtractTag<Input, Tag>
>
>(
tag: Tag,
reasonTag: ReasonTag
): Filter<
Input,
ExtractReason<
ExtractTag<Input, Tag>,
ReasonTag
>,
Input
>
<Tag extends string, ReasonTag extends string>(
tag: Tag,
reasonTag: ReasonTag
): <Input>(
input: Input
) => Result.Result<
ExtractReason<
ExtractTag<Input, Tag>,
ReasonTag
>,
Input
>
}
Creates a filter that extracts a reason from a tagged error.
reason: {
<function (type parameter) Input in <Input>(): <const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag) => Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Input>(): <const function (type parameter) Tag in <const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag): Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Tag extends type Tags<E> = E extends {
readonly _tag: string;
} ? E["_tag"] : never
Extracts the _tag string literal types from a union.
When to use
Use to get all discriminant values from a tagged union type.
Details
Members without a _tag field are ignored and produce never.
Example (Extracting tags)
import type { Types } from "effect"
type MyError =
| { readonly _tag: "NotFound"; readonly id: string }
| { readonly _tag: "Timeout"; readonly ms: number }
| string
type Result = Types.Tags<MyError>
// "NotFound" | "Timeout"
Tags<function (type parameter) Input in <Input>(): <const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag) => Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Input>, const function (type parameter) ReasonTag in <const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag): Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>ReasonTag extends type ReasonTags<E> = E extends {
readonly reason: {
readonly _tag: string;
};
} ? E["reason"]["_tag"] : never
Extracts the _tag values from the reason type of an error.
When to use
Use to get the discriminant values available inside a nested reason
error union.
Details
This is shorthand for Tags<ReasonOf<E>>. It returns never if E has no
reason field or the reason has no _tag.
Example (Getting reason tags)
import type { Types } from "effect"
type RateLimitError = { readonly _tag: "RateLimitError"; readonly retryAfter: number }
type QuotaError = { readonly _tag: "QuotaError"; readonly limit: number }
type ApiError = { readonly _tag: "ApiError"; readonly reason: RateLimitError | QuotaError }
type Result = Types.ReasonTags<ApiError>
// "RateLimitError" | "QuotaError"
ReasonTags<type ExtractTag<E, K extends string> = E extends {
readonly _tag: infer T;
} ? K extends T ? E : never : never
Extracts a specific member of a tagged union by its _tag value.
When to use
Use to select tagged-union members whose _tag matches a specific value in
type-level code.
Details
Returns never if no member matches the tag.
Example (Extracting a variant)
import type { Types } from "effect"
type MyError =
| { readonly _tag: "NotFound"; readonly id: string }
| { readonly _tag: "Timeout"; readonly ms: number }
type TimeoutError = Types.ExtractTag<MyError, "Timeout">
// { readonly _tag: "Timeout"; readonly ms: number }
ExtractTag<function (type parameter) Input in <Input>(): <const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag) => Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Input, function (type parameter) Tag in <const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag): Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Tag>>>(
tag: const Tag extends Tags<Input>tag: function (type parameter) Tag in <const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag): Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Tag,
reasonTag: const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>reasonTag: function (type parameter) ReasonTag in <const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag): Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>ReasonTag
) => interface Filter<in Input, out Pass = Input, out Fail = Input>Represents a filter function that can transform inputs to outputs or filter them out.
Details
A filter takes an input value and either returns a boxed pass value or the
special fail type to indicate the value should be filtered out.
Example (Defining a positive number filter)
import { Filter, Result } from "effect"
// A filter that only passes positive numbers
const positiveFilter: Filter.Filter<number> = (n) => n > 0 ? Result.succeed(n) : Result.fail(n)
console.log(positiveFilter(5)) // Result.succeed(5)
console.log(positiveFilter(-3)) // Result.fail(-3)
Filter<function (type parameter) Input in <Input>(): <const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag) => Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Input, type ExtractReason<E, K extends string> = E extends {
readonly reason: infer R;
} ? R extends {
readonly _tag: infer T;
} ? K extends T ? R : never : never : never
Extracts a specific reason variant by its _tag from an error's reason
field.
When to use
Use when you need the nested reason variant type itself, selected by _tag,
rather than the enclosing error type.
Details
Returns never if E has no matching reason variant.
Example (Extracting a reason variant)
import type { Types } from "effect"
type RateLimitError = { readonly _tag: "RateLimitError"; readonly retryAfter: number }
type QuotaError = { readonly _tag: "QuotaError"; readonly limit: number }
type ApiError = { readonly _tag: "ApiError"; readonly reason: RateLimitError | QuotaError }
type Result = Types.ExtractReason<ApiError, "RateLimitError">
// { readonly _tag: "RateLimitError"; readonly retryAfter: number }
ExtractReason<type ExtractTag<E, K extends string> = E extends {
readonly _tag: infer T;
} ? K extends T ? E : never : never
Extracts a specific member of a tagged union by its _tag value.
When to use
Use to select tagged-union members whose _tag matches a specific value in
type-level code.
Details
Returns never if no member matches the tag.
Example (Extracting a variant)
import type { Types } from "effect"
type MyError =
| { readonly _tag: "NotFound"; readonly id: string }
| { readonly _tag: "Timeout"; readonly ms: number }
type TimeoutError = Types.ExtractTag<MyError, "Timeout">
// { readonly _tag: "Timeout"; readonly ms: number }
ExtractTag<function (type parameter) Input in <Input>(): <const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag) => Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Input, function (type parameter) Tag in <const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag): Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Tag>, function (type parameter) ReasonTag in <const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag): Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>ReasonTag>, function (type parameter) Input in <Input>(): <const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag) => Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Input>
<function (type parameter) Input in <Input, const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag): Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Input, const function (type parameter) Tag in <Input, const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag): Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Tag extends type Tags<E> = E extends {
readonly _tag: string;
} ? E["_tag"] : never
Extracts the _tag string literal types from a union.
When to use
Use to get all discriminant values from a tagged union type.
Details
Members without a _tag field are ignored and produce never.
Example (Extracting tags)
import type { Types } from "effect"
type MyError =
| { readonly _tag: "NotFound"; readonly id: string }
| { readonly _tag: "Timeout"; readonly ms: number }
| string
type Result = Types.Tags<MyError>
// "NotFound" | "Timeout"
Tags<function (type parameter) Input in <Input, const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag): Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Input>, const function (type parameter) ReasonTag in <Input, const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag): Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>ReasonTag extends type ReasonTags<E> = E extends {
readonly reason: {
readonly _tag: string;
};
} ? E["reason"]["_tag"] : never
Extracts the _tag values from the reason type of an error.
When to use
Use to get the discriminant values available inside a nested reason
error union.
Details
This is shorthand for Tags<ReasonOf<E>>. It returns never if E has no
reason field or the reason has no _tag.
Example (Getting reason tags)
import type { Types } from "effect"
type RateLimitError = { readonly _tag: "RateLimitError"; readonly retryAfter: number }
type QuotaError = { readonly _tag: "QuotaError"; readonly limit: number }
type ApiError = { readonly _tag: "ApiError"; readonly reason: RateLimitError | QuotaError }
type Result = Types.ReasonTags<ApiError>
// "RateLimitError" | "QuotaError"
ReasonTags<type ExtractTag<E, K extends string> = E extends {
readonly _tag: infer T;
} ? K extends T ? E : never : never
Extracts a specific member of a tagged union by its _tag value.
When to use
Use to select tagged-union members whose _tag matches a specific value in
type-level code.
Details
Returns never if no member matches the tag.
Example (Extracting a variant)
import type { Types } from "effect"
type MyError =
| { readonly _tag: "NotFound"; readonly id: string }
| { readonly _tag: "Timeout"; readonly ms: number }
type TimeoutError = Types.ExtractTag<MyError, "Timeout">
// { readonly _tag: "Timeout"; readonly ms: number }
ExtractTag<function (type parameter) Input in <Input, const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag): Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Input, function (type parameter) Tag in <Input, const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag): Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Tag>>>(
tag: const Tag extends Tags<Input>tag: function (type parameter) Tag in <Input, const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag): Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Tag,
reasonTag: const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>reasonTag: function (type parameter) ReasonTag in <Input, const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag): Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>ReasonTag
): interface Filter<in Input, out Pass = Input, out Fail = Input>Represents a filter function that can transform inputs to outputs or filter them out.
Details
A filter takes an input value and either returns a boxed pass value or the
special fail type to indicate the value should be filtered out.
Example (Defining a positive number filter)
import { Filter, Result } from "effect"
// A filter that only passes positive numbers
const positiveFilter: Filter.Filter<number> = (n) => n > 0 ? Result.succeed(n) : Result.fail(n)
console.log(positiveFilter(5)) // Result.succeed(5)
console.log(positiveFilter(-3)) // Result.fail(-3)
Filter<function (type parameter) Input in <Input, const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag): Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Input, type ExtractReason<E, K extends string> = E extends {
readonly reason: infer R;
} ? R extends {
readonly _tag: infer T;
} ? K extends T ? R : never : never : never
Extracts a specific reason variant by its _tag from an error's reason
field.
When to use
Use when you need the nested reason variant type itself, selected by _tag,
rather than the enclosing error type.
Details
Returns never if E has no matching reason variant.
Example (Extracting a reason variant)
import type { Types } from "effect"
type RateLimitError = { readonly _tag: "RateLimitError"; readonly retryAfter: number }
type QuotaError = { readonly _tag: "QuotaError"; readonly limit: number }
type ApiError = { readonly _tag: "ApiError"; readonly reason: RateLimitError | QuotaError }
type Result = Types.ExtractReason<ApiError, "RateLimitError">
// { readonly _tag: "RateLimitError"; readonly retryAfter: number }
ExtractReason<type ExtractTag<E, K extends string> = E extends {
readonly _tag: infer T;
} ? K extends T ? E : never : never
Extracts a specific member of a tagged union by its _tag value.
When to use
Use to select tagged-union members whose _tag matches a specific value in
type-level code.
Details
Returns never if no member matches the tag.
Example (Extracting a variant)
import type { Types } from "effect"
type MyError =
| { readonly _tag: "NotFound"; readonly id: string }
| { readonly _tag: "Timeout"; readonly ms: number }
type TimeoutError = Types.ExtractTag<MyError, "Timeout">
// { readonly _tag: "Timeout"; readonly ms: number }
ExtractTag<function (type parameter) Input in <Input, const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag): Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Input, function (type parameter) Tag in <Input, const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag): Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Tag>, function (type parameter) ReasonTag in <Input, const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag): Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>ReasonTag>, function (type parameter) Input in <Input, const Tag extends Tags<Input>, const ReasonTag extends ReasonTags<ExtractTag<Input, Tag>>>(tag: Tag, reasonTag: ReasonTag): Filter<Input, ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Input>
<const function (type parameter) Tag in <const Tag extends string, const ReasonTag extends string>(tag: Tag, reasonTag: ReasonTag): <Input>(input: Input) => Result.Result<ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Tag extends string, const function (type parameter) ReasonTag in <const Tag extends string, const ReasonTag extends string>(tag: Tag, reasonTag: ReasonTag): <Input>(input: Input) => Result.Result<ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>ReasonTag extends string>(
tag: const Tag extends stringtag: function (type parameter) Tag in <const Tag extends string, const ReasonTag extends string>(tag: Tag, reasonTag: ReasonTag): <Input>(input: Input) => Result.Result<ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Tag,
reasonTag: const ReasonTag extends stringreasonTag: function (type parameter) ReasonTag in <const Tag extends string, const ReasonTag extends string>(tag: Tag, reasonTag: ReasonTag): <Input>(input: Input) => Result.Result<ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>ReasonTag
): <function (type parameter) Input in <Input>(input: Input): Result.Result<ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Input>(input: Inputinput: function (type parameter) Input in <Input>(input: Input): Result.Result<ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Input) => import ResultResult.type Result<A, E = never> = Result.Success<A, E> | Result.Failure<A, E>A value that is either Success<A, E> or Failure<A, E>.
When to use
Use when both success and failure should remain available as data and
Option would lose failure information.
Details
- Use
succeed
/
fail
to construct
- Use
match
to fold both branches
- Use
isSuccess
/
isFailure
to narrow the type
E defaults to never, so Result<number> means a result that cannot fail.
Example (Creating and matching a Result)
import { Result } from "effect"
const success = Result.succeed(42)
const failure = Result.fail("something went wrong")
const message = Result.match(success, {
onSuccess: (value) => `Success: ${value}`,
onFailure: (error) => `Error: ${error}`
})
console.log(message)
// Output: "Success: 42"
Namespace containing type-level utilities for extracting the inner types
of a Result.
Example (Extracting inner types)
import type { Result } from "effect"
type R = Result.Result<number, string>
// number
type A = Result.Result.Success<R>
// string
type E = Result.Result.Failure<R>
Result<type ExtractReason<E, K extends string> = E extends {
readonly reason: infer R;
} ? R extends {
readonly _tag: infer T;
} ? K extends T ? R : never : never : never
Extracts a specific reason variant by its _tag from an error's reason
field.
When to use
Use when you need the nested reason variant type itself, selected by _tag,
rather than the enclosing error type.
Details
Returns never if E has no matching reason variant.
Example (Extracting a reason variant)
import type { Types } from "effect"
type RateLimitError = { readonly _tag: "RateLimitError"; readonly retryAfter: number }
type QuotaError = { readonly _tag: "QuotaError"; readonly limit: number }
type ApiError = { readonly _tag: "ApiError"; readonly reason: RateLimitError | QuotaError }
type Result = Types.ExtractReason<ApiError, "RateLimitError">
// { readonly _tag: "RateLimitError"; readonly retryAfter: number }
ExtractReason<type ExtractTag<E, K extends string> = E extends {
readonly _tag: infer T;
} ? K extends T ? E : never : never
Extracts a specific member of a tagged union by its _tag value.
When to use
Use to select tagged-union members whose _tag matches a specific value in
type-level code.
Details
Returns never if no member matches the tag.
Example (Extracting a variant)
import type { Types } from "effect"
type MyError =
| { readonly _tag: "NotFound"; readonly id: string }
| { readonly _tag: "Timeout"; readonly ms: number }
type TimeoutError = Types.ExtractTag<MyError, "Timeout">
// { readonly _tag: "Timeout"; readonly ms: number }
ExtractTag<function (type parameter) Input in <Input>(input: Input): Result.Result<ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Input, function (type parameter) Tag in <const Tag extends string, const ReasonTag extends string>(tag: Tag, reasonTag: ReasonTag): <Input>(input: Input) => Result.Result<ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Tag>, function (type parameter) ReasonTag in <const Tag extends string, const ReasonTag extends string>(tag: Tag, reasonTag: ReasonTag): <Input>(input: Input) => Result.Result<ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>ReasonTag>, function (type parameter) Input in <Input>(input: Input): Result.Result<ExtractReason<ExtractTag<Input, Tag>, ReasonTag>, Input>Input>
} = function() {
return function (local var) arguments: IArgumentsarguments.IArguments.length: numberlength === 0 ? const reasonImpl: <
Tag extends string,
ReasonTag extends string
>(
tag: Tag,
reasonTag: ReasonTag
) => <Input>(
input: Input
) => Result.Result<
ExtractTag<Input, Tag>,
ExcludeTag<Input, Tag>
>
const reasonImpl: <
Tag extends string,
ReasonTag extends string
>(
tag: Tag,
reasonTag: ReasonTag
) => <Input>(
input: Input
) => Result.Result<
ExtractTag<Input, Tag>,
ExcludeTag<Input, Tag>
>
function (local var) arguments: IArgumentsarguments[0] as any, function (local var) arguments: IArgumentsarguments[1] as any)
} as any