I have a React component called HandleQuery
that handles the results of an Apollo GraphQL query:
import React, { ReactNode } from 'react';
import { CenteredMessage } from './centered-message';
export interface HandleQueryProps {
loading: boolean,
error?: Error,
children: ReactNode
}
export const HandleQuery = ({ loading, error, children }: HandleQueryProps) => {
if (loading) {
return <CenteredMessage>Loading...</CenteredMessage>;
}
if (error) {
return <CenteredMessage>{error.message}</CenteredMessage>;
}
return children;
};
When this component is used in another component it does not compile:
import React from 'react';
import { useQuery } from 'react-apollo-hooks';
import gql from 'graphql-tag';
import { HandleQuery } from '..';
import { MutationType } from '../../graphql-types';
import { AuthorsPanel } from './authors-panel';
import { GET_AUTHORS } from './authors-queries';
import { AuthorMutated } from './__generated__/AuthorMutated';
export class AuthorsContainer extends React.Component {
render() {
const { loading, error, data } = useQuery(GET_AUTHORS);
return (
<!-- THIS LINE PRODUCES A COMPILER ERROR -->
<HandleQuery loading={loading} error={error}>
<AuthorsPanel data={data} />
</HandleQuery>
);
}
}
The use of HandleQuery
above produces the following error:
Type error: JSX element type '{} | null | undefined' is not a constructor function for JSX elements. Type 'undefined' is not assignable to type 'Element | null'. TS2605
What does this mean and how can I get rid of it?
Update
Converting AuthorsContainer to a function component does not eliminate the error:
export const AuthorsContainer = () => {
const { loading, error, data } = useQuery(GET_AUTHORS);
return (
<HandleQuery loading={loading} error={error}>
<AuthorsPanel data={data} />
</HandleQuery>
);
};
Update 2 Implemented suggestion from @FredyC:
import React from 'react';
import { CenteredMessage } from './centered-message';
export interface HandleQueryProps {
loading: boolean;
error?: Error;
}
export const HandleQuery: React.FC<HandleQueryProps> = ({
loading,
error,
children
}) => {
if (loading) {
return <CenteredMessage>Loading...</CenteredMessage>;
}
if (error) {
return <CenteredMessage>{error.message}</CenteredMessage>;
}
return children;
};
Now the error on the container component has gone away, but a new compiler error has popped up on the HandleQuery
component:
Type error: Type '({ loading, error, children }: PropsWithChildren<HandleQueryProps>) => {} | null | undefined' is not assignable to type 'FunctionComponent<HandleQueryProps>'.
Type '{} | null | undefined' is not assignable to type 'ReactElement<any, string | ((props: any) => ReactElement<any, string | ... | (new (props: any) => Component<any, any, any>)> | null) | (new (props: any) => Component<any, any, any>)> | null'.
Type 'undefined' is not assignable to type 'ReactElement<any, string | ((props: any) => ReactElement<any, string | ... | (new (props: any) => Component<any, any, any>)> | null) | (new (props: any) => Component<any, any, any>)> | null'. TS2322
There is a long term issue regarding ReactNode. I don't understand specifics, but it's something hard-wired in TypeScript itself and is being worked on.
Either way, a solution should be easy. Don't use ReactNode with functional components :) The children
prop is implicitly included in React.FC type.
The same problem goes with returning children. It can be either overcome by wrapping into <React.Fragment>
or <div>
if you prefer, but since it's just a type error, you can convince TypeScript that you know what you are doing :)
import React, { ReactNode } from 'react';
import { CenteredMessage } from './centered-message';
export interface HandleQueryProps {
loading: boolean,
error?: Error,
}
export const HandleQuery: React.FC<HandleQueryProps> = ({ loading, error, children }) => {
if (loading) {
return <CenteredMessage>Loading...</CenteredMessage>;
}
if (error) {
return <CenteredMessage>{error.message}</CenteredMessage>;
}
return children as ReactElement<any>;
};