Assigning a type to a property that is a nested type of a Maybe type

Question

I'm trying to assign to a property a type generated by the graphql-codegen tool. The type I'm trying to assign is a nested type. Given the following type:

type SomeType = {
  someKey: Maybe<
    { __typename?: "OtherType" | undefined } & 
    { someNestedKey: ({ __typename?: "AnotherType" | undefined } & Pick<AnotherType, "prop1" | "prop2">)[] } 
  >
}

I need to be able to do:

myProperty: SomeType['someKey']['someNestedKey'] = []

However, the problem I'm running into is that the type of someKey is a Maybe type, so Typescript is complaining that there is no someNestedKey property on the <Maybe { __typename?: "OtherType" | ...} & { someNestedKey: (...)[] }> type (i.e., the type of someKey).

In Typescript, you can use the ! method to state that you know for sure that the property value of a type that is union'ed with undefined and/or null does, in fact, exist in this case. Is there a way to do something similar when assigning a type?

Since I'm using the graphql-codegen tool, I don't have control of these types.

Answer 1

I just found the answer in the documentation. I need to use the NonNullable type.

myProperty: NonNullable<SomeType['someKey']>['someNestedKey'] = []

Reference: https://www.typescriptlang.org/docs/handbook/utility-types.html#nonnullablet