Compose React context providers

README.md

Example

See it in action at https://codesandbox.io/s/n6txl.

The Problem

Have you ever come across a tree like this:

<ContextA.Provider>
  <ContextB.Provider>
    <ContextC.Provider>
      ...
    </ContextC.Provider>
  </ContextB.Provider>
</ContextA.Provider>

Instead, we can compose/combine this list of providers:

<Compose items={[
  [ContextA, props],
  [ContextB, props],
  [ContextC, props],
]}>
  ...
</Compose>

App.js

import React from "react";
import Compose from "./Compose.js";
import Context from "./Context.js";

export default function App() {
  const [foo] = React.useState(1);
  const [bar] = React.useState(2);

  return (
    <Compose
      items={[
        [Context, { foo, bar }],
      ]}
    >
      <Context.Consumer />
    </Compose>
  );
}

Compose.js

import React from "react";

export default function Compose({ items, children }) {
  return items.reduceRight(
    (acc, [Context, props]) =>
      React.createElement(Context.Provider, props, acc),
    children
  );
}

Context.js

import React from "react";

const Context = React.createContext();

function Consumer() {
  const value = React.useContext(Context);

  return <pre>Value: {JSON.stringify(value)}</pre>;
  // Value: {"foo":1,"bar":2}
}

function Provider({ children, ...props }) {
  return <Context.Provider value={props}>{children}</Context.Provider>;
}

export default { Context, Provider, Consumer };

thanks!!!, it was helpful to me, I'm using jest to test, now with this gist I can compose different wrapper depending of the test 👏 👏 👏

Hey! Here is a TS version. Could be helpful for someone:

interface ComponentComposerProps<T> {
  items: Array<[FC<T>, T] | FC<PropsWithChildren>>;
  children: ReactNode;
}

const ComponentComposer = <T extends PropsWithChildren>({
  items,
  children,
}: ComponentComposerProps<T>): ReactNode =>
  items.reduceRight<ReactNode>((acc, item) => {
    if (Array.isArray(item)) {
      const [Component, props] = item;

      return <Component {...props} />;
    }

    const Component = item;

    return <Component>{acc}</Component>;
  }, children);

Or the tough way for typescript compose

type JEC<T> = JSXElementConstructor<T>;
type CP<T extends keyof JSX.IntrinsicElements | JEC<any>> = Partial<ComponentProps<T>>;
interface ComposeFn {
  <
    A extends JEC<any>,
    B extends JEC<any>,
    C extends JEC<any>,
    D extends JEC<any>,
    E extends JEC<any>,
    F extends JEC<any>,
  >(p: {
    providers: [[A, CP<A>], [B, CP<B>], [C, CP<C>], [D, CP<D>], [E, CP<E>], [F, CP<F>]];
    children?: ReactNode;
  }): ReactElement;
  <A extends JEC<any>, B extends JEC<any>, C extends JEC<any>, D extends JEC<any>, E extends JEC<any>>(p: {
    providers: [[A, CP<A>], [B, CP<B>], [C, CP<C>], [D, CP<D>], [E, CP<E>]];
    children?: ReactNode;
  }): ReactElement;
  <A extends JEC<any>, B extends JEC<any>, C extends JEC<any>, D extends JEC<any>>(p: {
    providers: [[A, CP<A>], [B, CP<B>], [C, CP<C>], [D, CP<D>]];
    children?: ReactNode;
  }): ReactElement;
  <A extends JEC<any>, B extends JEC<any>, C extends JEC<any>>(p: {
    providers: [[A, CP<A>], [B, CP<B>], [C, CP<C>]];
    children?: ReactNode;
  }): ReactElement;
  <A extends JEC<any>, B extends JEC<any>>(p: {
    providers: [[A, CP<A>], [B, CP<B>]];
    children?: ReactNode;
  }): ReactElement;
  <A extends JEC<any>>(p: { providers: [[A, CP<A>]]; children?: ReactNode }): ReactElement;
  <T extends JEC<any>>(p: { providers: [T, CP<T>][]; children?: ReactNode }): ReactElement;
}
const Compose: ComposeFn = ({ providers, children }: { providers: [JEC<any>, any][]; children?: ReactNode }) =>
  providers.reduceRight((acc, [Wrapper, props]) => React.createElement(Wrapper, props, acc), children) as ReactElement;

Hey @samMeow! Could you please explain what the advantages of this approach are? Your code looks much complicated than my and has restriction - only 6 nested components. And what is the type ComponentsProps?

Hey @samMeow! Could you please explain what the advantages of this approach are? Your code looks much complicated than my and has restriction - only 6 nested components. And what is the type ComponentsProps?

The advantage of above code is to allow Providers to have different type, and each items would check against itself for props, while using only one generic T, will limit to only one kind of Provider
https://codesandbox.io/p/sandbox/sharp-bohr-cwh4ff?file=%2Fsrc%2FApp.tsx%3A27%2C19

It actually support more than 6 nested components with last bit T type as fallback, but it will lose the ability to check type for each items. I use 6 here just good enough for most case, so feel free to add more.

ComponentsProps my bad typos, changed to ComponentProps,

// https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/react/index.d.ts#L1653
type ComponentProps<T extends keyof JSX.IntrinsicElements | JSXElementConstructor<any>> = T extends
        JSXElementConstructor<infer P> ? P
        : T extends keyof JSX.IntrinsicElements ? JSX.IntrinsicElements[T]
        : {};

p.s. still waiting a better Utility Type for compose in typescript (ref: https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/lodash/fp.d.ts#L304)