nonEmptyArray - API reference

API reference › @evolu/common › Type › nonEmptyArray

function nonEmptyArray<
  ParentType extends AnyType & {
    Output: readonly unknown[];
  },
>(
  parent: ValidateBrandParent<"NonEmptyArray", ParentType>,
): Type<"NonEmptyArray">;

Defined in: packages/common/src/Type.ts:13306

Adds non-empty validation to an existing array Type.

Narrows the Output to a NonEmptyReadonlyArray while preserving the parent Type's constraints and brands, so functions that require a non-empty array accept it without another check. Validation leaves the array unchanged. For strings, use minLength.

Example

import {
  assertEqual,
  assertErr,
  assertOk,
  array,
  firstInArray,
  nonEmptyArray,
  String,
} from "@evolu/common";

const Tags = nonEmptyArray(array(String));

const tags = Tags.fromUnknown(["local-first", "offline"]);
assertOk(tags, ["local-first", "offline"]);
assertEqual(firstInArray(tags.value), "local-first");

const invalid = Tags.fromUnknown([]);
assertErr(invalid, { type: "NonEmptyArray", value: [] });
assertEqual(
  Tags.formatError(invalid.error),
  "The value [] must contain at least one item.",
);