prefer-type-fest-set-required
Require TypeFest SetRequired<T, Keys> over imported aliases like
RequiredBy.
Targeted pattern scopeโ
This rule scopes matching to imported legacy aliases that model the same semantics as SetRequired<T, Keys>.
- Type references that resolve to imported
RequiredByaliases.
Locally defined lookalikes or unrelated type references are excluded unless they resolve to the targeted imported alias.
What this rule reportsโ
This rule reports imported alias usages that should migrate to SetRequired<T, Keys>.
- Type references that resolve to imported
RequiredByaliases.
Why this rule existsโ
SetRequired is the canonical TypeFest utility for making selected keys
required. Standardizing on TypeFest naming reduces semantic drift between
utility libraries.
โ Incorrectโ
import type { RequiredBy } from "type-aliases";
type CompleteUser = RequiredBy<User, "id">;
โ Correctโ
import type { SetRequired } from "type-fest";
type CompleteUser = SetRequired<User, "id">;
Behavior and migration notesโ
SetRequired<T, Keys>forces selected optional keys to be required.- This rule targets imported aliases with equivalent semantics (
RequiredBy). - Use this utility in post-validation and persisted-domain types where selected fields become mandatory.
Additional examplesโ
โ Incorrect โ Additional exampleโ
import type { RequiredBy } from "type-aliases";
type Complete = RequiredBy<User, "id">;
โ Correct โ Additional exampleโ
import type { SetRequired } from "type-fest";
type Complete = SetRequired<User, "id">;
โ Correct โ Repository-wide usageโ
type Persisted = SetRequired<Order, "id" | "status">;
ESLint flat config exampleโ
import typefest from "eslint-plugin-typefest";
export default [
{
plugins: { typefest },
rules: {
"typefest/prefer-type-fest-set-required": "error",
},
},
];
When not to use itโ
Disable this rule if existing exported alias names are part of a compatibility contract.
Package documentationโ
TypeFest package documentation:
Source file: source/set-required.d.ts
/**
* Create a type that makes the given keys required. The remaining keys are kept
* as is. The sister of the `SetOptional` type.
*
* Use-case: You want to define a single model where the only thing that changes
* is whether or not some of the keys are required.
*
* @category Object
*
* @example
* ```
* import type {SetRequired} from 'type-fest';
*
* type Foo = {
* a?: number;
* b: string;
* c?: boolean;
* };
*
* type SomeRequired = SetRequired<Foo, 'b' | 'c'>;
* // type SomeRequired = {
* // a?: number;
* // b: string; // Was already required and still is.
* // c: boolean; // Is now required.
* // }
*
* // Set specific indices in an array to be required.
* type ArrayExample = SetRequired<[number?, number?, number?], 0 | 1>;
* //=> [number, number, number?]
* ```;
*/
Rule catalog ID: R065