--- /dev/null
+import {Except} from './except';
+
+/**
+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.
+
+@example
+```
+import {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.
+// }
+```
+*/
+export type SetRequired<BaseType, Keys extends keyof BaseType = keyof BaseType> =
+ // Pick just the keys that are not required from the base type.
+ Except<BaseType, Keys> &
+ // Pick the keys that should be required from the base type and make them required.
+ Required<Pick<BaseType, Keys>> extends
+ // If `InferredType` extends the previous, then for each key, use the inferred type key.
+ infer InferredType
+ ? {[KeyType in keyof InferredType]: InferredType[KeyType]}
+ : never;