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effect-extras

PredicateX overview

Generic, framework-agnostic extensions to Effect’s Predicate module.

Added in v0.0.0

Table of contents

pattern matching

matchRefine

Runs a refinement against value and branches on the result, passing the narrowed value to the whenTrue handler.

It pairs a Predicate.Refinement<A, B> with two continuations so the success branch receives value already narrowed to B, replacing an if/else that would otherwise re-check or cast. Supports both data-first and data-last (pipeable) call styles.

Signature

export declare const matchRefine: (<A, B extends A, C>(
  predicate: Predicate.Refinement<A, B>,
  handlers: { whenFalse: () => C; whenTrue: (value: B) => C }
) => (value: A) => C) &
  (<A, B extends A, C>(
    value: A,
    predicate: Predicate.Refinement<A, B>,
    handlers: { whenFalse: () => C; whenTrue: (value: B) => C }
  ) => C)

Example

import { PredicateX } from "@nunofyobiz/effect-extras"
import { Predicate, pipe } from "effect"

// Data-first
assert.deepStrictEqual(
  PredicateX.matchRefine("hello", Predicate.isString, {
    whenTrue: (value) => `String: ${value}`,
    whenFalse: () => "Not a string"
  }),
  "String: hello"
)

// Data-last (pipeable)
assert.deepStrictEqual(
  pipe(
    42,
    PredicateX.matchRefine(Predicate.isString, {
      whenTrue: (value) => `String: ${value}`,
      whenFalse: () => "Not a string"
    })
  ),
  "Not a string"
)

Added in v0.0.0

refinements

isNonEmptyString

Refines an unknown value to a non-empty string, returning true only when the value is present, is a string, and has at least one character.

This is the compound guard the repo’s conventions call for: it folds Predicate.isNotNullish, Predicate.isString, and String.isNonEmpty into a single reusable refinement so call sites get value is string narrowing without restating the three checks.

Signature

export declare function isNonEmptyString(value: unknown): value is string

Example

import { PredicateX } from "@nunofyobiz/effect-extras"

assert.deepStrictEqual(PredicateX.isNonEmptyString("hello"), true)
assert.deepStrictEqual(PredicateX.isNonEmptyString(""), false)
assert.deepStrictEqual(PredicateX.isNonEmptyString(null), false)
assert.deepStrictEqual(PredicateX.isNonEmptyString(123), false)

Added in v0.0.0

unsafeIsRecord

Refines an unknown value to a plain Record<string, unknown> — true only for a non-null, non-array object whose prototype is Object.prototype (an object literal) or null (an Object.create(null) map).

Effect ships no Predicate.isRecord. Predicate.isObject is the closest, but it also accepts Map, Set, Date, RegExp, and class instances. This guard adds a prototype check to rule those out, narrowing to Record<string, unknown> so the JSON-tree helpers (RecordX.deepMerge, RecordX.canonicalize, RecordX.deleteByPath) can compose without an as cast.

It is named unsafe because the narrowing comes purely from the value’s runtime shape — it does not validate the key or value types. A symbol-keyed entry still passes despite the string key claim, and values are asserted unknown without any check. Treat it as a structural convenience, not a Schema validation: reach for Schema when you need real key/value guarantees.

Signature

export declare function unsafeIsRecord(value: unknown): value is Record<string, unknown>

Example

import { PredicateX } from "@nunofyobiz/effect-extras"

assert.deepStrictEqual(PredicateX.unsafeIsRecord({ a: 1 }), true)
assert.deepStrictEqual(PredicateX.unsafeIsRecord(Object.create(null)), true)
assert.deepStrictEqual(PredicateX.unsafeIsRecord([1, 2]), false)
assert.deepStrictEqual(PredicateX.unsafeIsRecord(new Map()), false)
assert.deepStrictEqual(PredicateX.unsafeIsRecord(null), false)

Added in v0.0.0