optionalKey<S>Type-level representation returned by optionalKey.
export interface interface optionalKey<S extends Constraint>Type-level representation returned by
optionalKey
.
Creates an exact optional key schema for struct fields. Unlike optional,
this creates exact optional properties (not | undefined) that can be
completely omitted from the object.
Example (Creating a struct with optional key)
import { Schema } from "effect"
const schema = Schema.Struct({
name: Schema.String,
age: Schema.optionalKey(Schema.Number)
})
// Type: { readonly name: string; readonly age?: number }
type Person = typeof schema["Type"]
optionalKey<function (type parameter) S in optionalKey<S extends Constraint>S extends Constraint> extends
interface BottomLazy<out Ast extends SchemaAST.AST, out Rebuild extends Top, in out TypeParameters extends ReadonlyArray<Constraint> = readonly [], out TypeMutability extends Mutability = "readonly", out TypeOptionality extends Optionality = "required", out TypeConstructorDefault extends ConstructorDefault = "no-default", out EncodedMutability extends Mutability = "readonly", out EncodedOptionality extends Optionality = "required">Lazy Bottom variant for schema implementations that compute their public
views on demand.
When to use
Use as an implementation base for schema interfaces that must expose
Bottom behavior without forcing TypeScript to eagerly evaluate expensive
Type, Encoded, or service views.
Details
The laziness is purely type-level; runtime behavior is unchanged.
BottomLazy keeps the structural operations inherited from Bottom, but
erases the expensive schema views to unknown. Concrete schema interfaces can
then redeclare the precise views they expose. This keeps wide schemas such as
Struct and Union cheaper when generic code reads a single view, while
preserving their exact public types.
BottomLazy<
function (type parameter) S in optionalKey<S extends Constraint>S["ast"],
interface optionalKey<S extends Constraint>Type-level representation returned by
optionalKey
.
Creates an exact optional key schema for struct fields. Unlike optional,
this creates exact optional properties (not | undefined) that can be
completely omitted from the object.
Example (Creating a struct with optional key)
import { Schema } from "effect"
const schema = Schema.Struct({
name: Schema.String,
age: Schema.optionalKey(Schema.Number)
})
// Type: { readonly name: string; readonly age?: number }
type Person = typeof schema["Type"]
optionalKey<function (type parameter) S in optionalKey<S extends Constraint>S>,
function (type parameter) S in optionalKey<S extends Constraint>S["~type.parameters"],
function (type parameter) S in optionalKey<S extends Constraint>S["~type.mutability"],
"optional",
function (type parameter) S in optionalKey<S extends Constraint>S["~type.constructor.default"],
function (type parameter) S in optionalKey<S extends Constraint>S["~encoded.mutability"],
"optional"
>
{
readonly "Type": function (type parameter) S in optionalKey<S extends Constraint>S["Type"]
readonly "Encoded": function (type parameter) S in optionalKey<S extends Constraint>S["Encoded"]
readonly "DecodingServices": function (type parameter) S in optionalKey<S extends Constraint>S["DecodingServices"]
readonly "EncodingServices": function (type parameter) S in optionalKey<S extends Constraint>S["EncodingServices"]
readonly "~type.make.in": function (type parameter) S in optionalKey<S extends Constraint>S["~type.make.in"]
readonly "~type.make": function (type parameter) S in optionalKey<S extends Constraint>S["~type.make"]
readonly "Iso": function (type parameter) S in optionalKey<S extends Constraint>S["Iso"]
readonly optionalKey<S extends Constraint>.schema: S extends Constraintschema: function (type parameter) S in optionalKey<S extends Constraint>S
}
interface optionalKeyLambda extends Lambda {
<function (type parameter) S in <S extends Constraint>(self: S): optionalKey<S>S extends Constraint>(self: S extends Constraintself: function (type parameter) S in <S extends Constraint>(self: S): optionalKey<S>S): interface optionalKey<S extends Constraint>Type-level representation returned by
optionalKey
.
Creates an exact optional key schema for struct fields. Unlike optional,
this creates exact optional properties (not | undefined) that can be
completely omitted from the object.
Example (Creating a struct with optional key)
import { Schema } from "effect"
const schema = Schema.Struct({
name: Schema.String,
age: Schema.optionalKey(Schema.Number)
})
// Type: { readonly name: string; readonly age?: number }
type Person = typeof schema["Type"]
optionalKey<function (type parameter) S in <S extends Constraint>(self: S): optionalKey<S>S>
readonly "~lambda.out": this["~lambda.in"] extends Constraint ? interface optionalKey<S extends Constraint>Type-level representation returned by
optionalKey
.
Creates an exact optional key schema for struct fields. Unlike optional,
this creates exact optional properties (not | undefined) that can be
completely omitted from the object.
Example (Creating a struct with optional key)
import { Schema } from "effect"
const schema = Schema.Struct({
name: Schema.String,
age: Schema.optionalKey(Schema.Number)
})
// Type: { readonly name: string; readonly age?: number }
type Person = typeof schema["Type"]
optionalKey<this["~lambda.in"]> : never
}
/**
* Creates an exact optional key schema for struct fields. Unlike `optional`,
* this creates exact optional properties (not `| undefined`) that can be
* completely omitted from the object.
*
* **Example** (Creating a struct with optional key)
*
* ```ts
* import { Schema } from "effect"
*
* const schema = Schema.Struct({
* name: Schema.String,
* age: Schema.optionalKey(Schema.Number)
* })
*
* // Type: { readonly name: string; readonly age?: number }
* type Person = typeof schema["Type"]
* ```
*
* @category combinators
* @since 4.0.0
*/
export const const optionalKey: optionalKeyLambdaType-level representation returned by
optionalKey
.
Creates an exact optional key schema for struct fields. Unlike optional,
this creates exact optional properties (not | undefined) that can be
completely omitted from the object.
Example (Creating a struct with optional key)
import { Schema } from "effect"
const schema = Schema.Struct({
name: Schema.String,
age: Schema.optionalKey(Schema.Number)
})
// Type: { readonly name: string; readonly age?: number }
type Person = typeof schema["Type"]
optionalKey = import Struct_Struct_.const lambda: <optionalKeyLambda>(
f: (a: Constraint) => optionalKey<Constraint>
) => optionalKeyLambda
Wraps a plain function as a
Lambda
value so it can be used with
When to use
Use to create a typed lambda for struct mapping APIs that need type-level
input and output tracking.
Details
The type parameter L encodes both the input and output types at the type
level, allowing the compiler to track how struct value types change. At
runtime, the returned value is the same function; lambda only adjusts the
type.
Example (Wrapping values in arrays)
import { pipe, Struct } from "effect"
interface AsArray extends Struct.Lambda {
<A>(self: A): Array<A>
readonly "~lambda.out": Array<this["~lambda.in"]>
}
const asArray = Struct.lambda<AsArray>((a) => [a])
const result = pipe({ x: 1, y: "hello" }, Struct.map(asArray))
console.log(result) // { x: [1], y: ["hello"] }
lambda<optionalKeyLambda>((schema: Constraint(parameter) schema: {
ast: SchemaAST.AST;
Type: unknown;
Encoded: unknown;
DecodingServices: unknown;
EncodingServices: unknown;
Iso: unknown;
}
const make: <S extends Constraint>(
ast: S["ast"],
options?: object
) => S
Creates a schema from an AST (Abstract Syntax Tree) node.
Details
This is the fundamental constructor for all schemas in the Effect Schema
library. It takes an AST node and wraps it in a fully-typed schema that
preserves all type information and provides the complete schema API.
The make function is used internally to create all primitive schemas like
String, Number, Boolean, etc., as well as more complex schemas. It's
the bridge between the untyped AST representation and the strongly-typed
schema.
make(import SchemaASTSchemaAST.function optionalKey<A extends AST>(
ast: A
): A
Marks an AST node's property key as optional by setting
Context.isOptional
to true.
Details
Also propagates the optional flag through the last link of the encoding
chain if present.
optionalKey(schema: Constraint(parameter) schema: {
ast: SchemaAST.AST;
Type: unknown;
Encoded: unknown;
DecodingServices: unknown;
EncodingServices: unknown;
Iso: unknown;
}
Constraint["ast"]: SchemaAST.ASTast), { schema: Constraint(property) schema: {
ast: SchemaAST.AST;
Type: unknown;
Encoded: unknown;
DecodingServices: unknown;
EncodingServices: unknown;
Iso: unknown;
}