type-a

Constraints

Constraints are reusable runtime predicates that can be attached to any field via the { is: … } option. They return true on success or an error string that is collected by schema.validate().

import { describe, it, expect } from "vitest";
import { Schema, one, constraints as c, typed as t } from "@rybosome/type-a";

describe("constraints.nonEmpty & .atMost", () => {
  it("rejects invalid data", () => {
    class Comment extends Schema.from({
      body: one(t.string, { is: c.nonEmpty }),
      rating: one(t.number, { is: c.atMost(5) }),
    }) {}

    const invalid = new Comment({ body: "", rating: 10 });
    const errs = invalid.validate();
    expect(errs.length).toBe(2);
  });
});

Under the hood, a constraint is just a function (v) => true | string, so you can author your own and compose them as needed.

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