<T, E extends T = T, R = never>(
f: (
options: SchemaAST.ParseOptions
) => Effect.Effect<Option.Option<T>, SchemaIssue.Issue, R>
): Getter<T, E, R>Creates a getter that handles the case when the input is absent (Option.None).
When to use
Use when you need a schema getter to provide a fallback or computed value for missing struct keys.
- Building custom "default value" logic more complex than withDefault.
Details
- When input is
None, callsfto produce the result. - When input is
Some, passes it through unchanged. freceives the parse options and may returnNoneto keep the value absent.
Example (Providing a default timestamp for a missing field)
import { Effect, Option, SchemaGetter } from "effect"
const withTimestamp = SchemaGetter.onNone<number>(() =>
Effect.succeed(Option.some(Date.now()))
)export function function onNone<
T,
E extends T = T,
R = never
>(
f: (
options: SchemaAST.ParseOptions
) => Effect.Effect<
Option.Option<T>,
SchemaIssue.Issue,
R
>
): Getter<T, E, R>
Creates a getter that handles the case when the input is absent (Option.None).
When to use
Use when you need a schema getter to provide a fallback or computed value for
missing struct keys.
- Building custom "default value" logic more complex than
withDefault
.
Details
- When input is
None, calls f to produce the result.
- When input is
Some, passes it through unchanged.
f receives the parse options and may return None to keep the value absent.
Example (Providing a default timestamp for a missing field)
import { Effect, Option, SchemaGetter } from "effect"
const withTimestamp = SchemaGetter.onNone<number>(() =>
Effect.succeed(Option.some(Date.now()))
)
onNone<function (type parameter) T in onNone<T, E extends T = T, R = never>(f: (options: SchemaAST.ParseOptions) => Effect.Effect<Option.Option<T>, SchemaIssue.Issue, R>): Getter<T, E, R>T, function (type parameter) E in onNone<T, E extends T = T, R = never>(f: (options: SchemaAST.ParseOptions) => Effect.Effect<Option.Option<T>, SchemaIssue.Issue, R>): Getter<T, E, R>E extends function (type parameter) T in onNone<T, E extends T = T, R = never>(f: (options: SchemaAST.ParseOptions) => Effect.Effect<Option.Option<T>, SchemaIssue.Issue, R>): Getter<T, E, R>T = function (type parameter) T in onNone<T, E extends T = T, R = never>(f: (options: SchemaAST.ParseOptions) => Effect.Effect<Option.Option<T>, SchemaIssue.Issue, R>): Getter<T, E, R>T, function (type parameter) R in onNone<T, E extends T = T, R = never>(f: (options: SchemaAST.ParseOptions) => Effect.Effect<Option.Option<T>, SchemaIssue.Issue, R>): Getter<T, E, R>R = never>(
f: (
options: SchemaAST.ParseOptions
) => Effect.Effect<
Option.Option<T>,
SchemaIssue.Issue,
R
>
options: SchemaAST.ParseOptions(parameter) options: {
errors: "first" | "all" | undefined;
onExcessProperty: "ignore" | "error" | "preserve" | undefined;
propertyOrder: "none" | "original" | undefined;
disableChecks: boolean | undefined;
concurrency: number | "unbounded" | undefined;
}
import SchemaASTSchemaAST.type SchemaAST.ParseOptions = /*unresolved*/ anyParseOptions) => import EffectEffect.type Effect.Effect = /*unresolved*/ anyEffect<import OptionOption.type Option.Option = /*unresolved*/ anyOption<function (type parameter) T in onNone<T, E extends T = T, R = never>(f: (options: SchemaAST.ParseOptions) => Effect.Effect<Option.Option<T>, SchemaIssue.Issue, R>): Getter<T, E, R>T>, import SchemaIssueSchemaIssue.type Issue =
| SchemaIssue.Leaf
| SchemaIssue.Filter
| SchemaIssue.Encoding
| SchemaIssue.Pointer
| SchemaIssue.Composite
| SchemaIssue.AnyOf
The root discriminated union of all validation error nodes.
When to use
Use when typing the error channel in Effect<A, Issue, R> results from
schema parsing, or when writing custom formatters or issue-tree walkers.
Details
Every node has a _tag field for pattern-matching. The union includes both
terminal
Leaf
types and composite types that wrap inner issues:
Filter
,
Encoding
,
Pointer
,
Composite
,
AnyOf
. All Issue instances have a toString() that delegates to
the default formatter, so String(issue) produces a human-readable message.
Issue, function (type parameter) R in onNone<T, E extends T = T, R = never>(f: (options: SchemaAST.ParseOptions) => Effect.Effect<Option.Option<T>, SchemaIssue.Issue, R>): Getter<T, E, R>R>
): class Getter<out T, in E, R = never>class Getter {
run: (input: Option.Option<E>, options: SchemaAST.ParseOptions) => Effect.Effect<Option.Option<T>, SchemaIssue.Issue, R>;
map: <T2>(f: (t: T) => T2) => Getter<T2, E, R>;
compose: <T2, R2>(other: Getter<T2, T, R2>) => Getter<T2, E, R | R2>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
Represents a composable transformation from an encoded type E to a decoded type T.
When to use
Use when you need a schema getter to build and compose custom transformations
for Schema.decodeTo or Schema.decode.
Details
A getter wraps a function Option<E> -> Effect<Option<T>, Issue, R>. It
receives Option.None when the encoded key is absent, such as a missing
struct field, and returns Option.None to omit the value from the decoded
output. It fails with Issue on invalid input and may require Effect
services via R. .map(f) applies f to the decoded value inside Some
while leaving None unchanged. .compose(other) chains two getters by
feeding the output of this into other; passthrough getters on either side
are optimized away.
Example (Creating and composing getters)
import { SchemaGetter } from "effect"
const parseNumber = SchemaGetter.transform<number, string>((s) => Number(s))
const double = SchemaGetter.transform<number, number>((n) => n * 2)
const composed = parseNumber.compose(double)
// composed: Getter<number, string> — parses then doubles
Getter<function (type parameter) T in onNone<T, E extends T = T, R = never>(f: (options: SchemaAST.ParseOptions) => Effect.Effect<Option.Option<T>, SchemaIssue.Issue, R>): Getter<T, E, R>T, function (type parameter) E in onNone<T, E extends T = T, R = never>(f: (options: SchemaAST.ParseOptions) => Effect.Effect<Option.Option<T>, SchemaIssue.Issue, R>): Getter<T, E, R>E, function (type parameter) R in onNone<T, E extends T = T, R = never>(f: (options: SchemaAST.ParseOptions) => Effect.Effect<Option.Option<T>, SchemaIssue.Issue, R>): Getter<T, E, R>R> {
return new constructor Getter<T, E, R>(run: (input: Option.Option<E>, options: SchemaAST.ParseOptions) => Effect.Effect<Option.Option<T>, SchemaIssue.Issue, R>): Getter<T, E, R>Represents a composable transformation from an encoded type E to a decoded type T.
When to use
Use when you need a schema getter to build and compose custom transformations
for Schema.decodeTo or Schema.decode.
Details
A getter wraps a function Option<E> -> Effect<Option<T>, Issue, R>. It
receives Option.None when the encoded key is absent, such as a missing
struct field, and returns Option.None to omit the value from the decoded
output. It fails with Issue on invalid input and may require Effect
services via R. .map(f) applies f to the decoded value inside Some
while leaving None unchanged. .compose(other) chains two getters by
feeding the output of this into other; passthrough getters on either side
are optimized away.
Example (Creating and composing getters)
import { SchemaGetter } from "effect"
const parseNumber = SchemaGetter.transform<number, string>((s) => Number(s))
const double = SchemaGetter.transform<number, number>((n) => n * 2)
const composed = parseNumber.compose(double)
// composed: Getter<number, string> — parses then doubles
Getter((ot: Option.Option<E>ot, options: SchemaAST.ParseOptions(parameter) options: {
errors: "first" | "all" | undefined;
onExcessProperty: "ignore" | "error" | "preserve" | undefined;
propertyOrder: "none" | "original" | undefined;
disableChecks: boolean | undefined;
concurrency: number | "unbounded" | undefined;
}
import OptionOption.isNone(ot: Option.Option<E>ot) ? f: (
options: SchemaAST.ParseOptions
) => Effect.Effect<
Option.Option<T>,
SchemaIssue.Issue,
R
>
options: SchemaAST.ParseOptions(parameter) options: {
errors: "first" | "all" | undefined;
onExcessProperty: "ignore" | "error" | "preserve" | undefined;
propertyOrder: "none" | "original" | undefined;
disableChecks: boolean | undefined;
concurrency: number | "unbounded" | undefined;
}
import EffectEffect.succeed(ot: Option.Some<E>(parameter) ot: {
_tag: "Some";
_op: "Some";
value: A;
valueOrUndefined: A;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}