Infer types of props returned by getStaticProps

Feature request

Right now I have to redeclare the types for page props injected by getStaticProps, although typescript already infers them correctly. We could create a type that infers them from the locally exported typeof getStaticProps.

Describe alternatives you’ve considered

I am by no means a TS expert, so I am not sure if there are better alternatives for inferring the types.

First working draft:

export type StaticPropsReturnValue<P> = {
    props: P;
    revalidate?: number | boolean;
  };

export type ResolvedGetStaticProps<T extends (...args: any) => any> =
    T extends (...args: any) => Promise<StaticPropsReturnValue<infer U>>
        ? StaticPropsReturnValue<U> : never;
        
export type StaticProps<T extends GetStaticProps> = ResolvedGetStaticProps<T>["props"];

used like this:

export const getStaticProps = async () => ({
    props: {
        propNumberOne: "hello world",
        propNumberTwo: 2,
    },
});


const TypesTest = ({ propNumberOne }: StaticProps<typeof getStaticProps>) => (<div>{propNumberOne}</div>);

we get correct type inference for our props.

Next steps:

• I would love to get feedback from TS experts if there is a better solution to do this
• if you like the feature I will gladly create a PR for this.

[lukebarton]

export const getServerSideProps = async ({ params }) => {
  return { 
    props: { foo: "bar" } 
  }
};

export const Page = (props: InferGetServerSidePropsType<typeof getServerSideProps>) => { ... }

causes props: never however the following works fine:

export const getServerSideProps = async ({ params }: GetServerSidePropsContext) => {
  return { 
    props: { foo: "bar" } 
  }
};

export const Page = (props: InferGetServerSidePropsType<typeof getServerSideProps>) => { ... }

and so does:

export const getServerSideProps = async (ctx) => {
  const params = ctx.params;
  return { 
    props: { foo: "bar" } 
  }
};

export const Page = (props: InferGetServerSidePropsType<typeof getServerSideProps>) => { ... }

[balazsorban44]

This issue has been automatically locked due to no recent activity. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.