Context.Reference<Metadata>Context reference containing metadata for the currently running execution-plan attempt.
When to use
Use to read the active plan step and attempt while code is running under an execution plan.
export const const CurrentMetadata: Context.Reference<Metadata>const CurrentMetadata: {
key: string;
Service: {
attempt: number;
stepIndex: number;
};
defaultValue: () => Shape;
of: (this: void, self: Metadata) => Metadata;
context: (self: Metadata) => Context.Context<never>;
use: (f: (service: Metadata) => Effect.Effect<A, E, R>) => Effect.Effect<A, E, R>;
useSync: (f: (service: Metadata) => A) => Effect.Effect<A, never, never>;
Identifier: Identifier;
stack: string | undefined;
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;
}
Context reference containing metadata for the currently running
execution-plan attempt.
When to use
Use to read the active plan step and attempt while code is running under an
execution plan.
CurrentMetadata = import ContextContext.const Reference: <Service>(
key: string,
options: {
readonly defaultValue: () => Service
}
) => Reference<Service>
Creates a context key with a default value.
When to use
Use when you need to define a context key with a lazily computed default
value.
Details
Context.Reference allows you to create a key that can hold a value. You
can provide a default value for the service, which will automatically be used
when the context is accessed, or override it with a custom implementation
when needed. The default value is computed lazily and cached on the
reference.
Example (Creating references with default values)
import { Context } from "effect"
// Create a reference with a default value
const LoggerRef = Context.Reference("Logger", {
defaultValue: () => ({ log: (msg: string) => console.log(msg) })
})
// The reference provides the default value when accessed from an empty context
const context = Context.empty()
const logger = Context.get(context, LoggerRef)
// You can also override the default value
const customContext = Context.make(LoggerRef, {
log: (msg: string) => `Custom: ${msg}`
})
const customLogger = Context.get(customContext, LoggerRef)
Reference<Metadata>("effect/ExecutionPlan/CurrentMetadata", {
defaultValue: LazyArg<{
attempt: number
stepIndex: number
}>
constant<A>(value: A): LazyArg<A>Creates a zero-argument function that always returns the provided value.
When to use
Use when you need a thunk or callback that returns the same value on every
invocation.
Example (Creating a constant thunk)
import { Function } from "effect"
import * as assert from "node:assert"
const constNull = Function.constant(null)
assert.deepStrictEqual(constNull(), null)
assert.deepStrictEqual(constNull(), null)
constant({
attempt: numberattempt: 0,
stepIndex: numberstepIndex: 0
})
})