fix: allow partial classes prop in withStyles

[Dru89]

The classes prop created by the withStyles function is meant to be an optional parameter where you can provide some or all of the style classes.

Imagine a somewhat contrived snippet like:

import React from "react";
import withStyles, { WithStylesProps } from "react-jss";
import clsx from "clsx";

const styles = {
  root: { display: "block" },
  blue: { color: "blue" },
};

type Props = { blue?: boolean } & WithStylesProps<typeof styles>;
const Component = ({ blue = false, classes }: Props) => (
  <div className={clsx(classes.root, { [classes.blue]: blue })}>
    Hello, world!
  </div>
);

const StyledComponent = withStyles(styles)(Component);

You'd expect to be able to use it in any of the following ways:

<StyledComponent />
<StyledComponent blue />
<StyledComponent classes={{ root: "myClass" }} />

The last use case was broken in TypeScript because, while classes was an optional prop, each key within class was required. So you'd get an error like:

Property 'blue' is missing in type '{ root: string; }' but required in type 'Record<"blue" | "root", string>'.ts(2741)

This changes makes sure that the classes property is still optional, but that each key within it is optional, too. I abstracted a field out so that I could use it in two places. There's probably about a dozen ways to set something like this up, though, so if you'd prefer it formatted in a different way let me know.

[Dru89]

As a side note, I tried following all of the steps in CONTRIBUTING.md, but several of the steps don't seem to work anymore.

There's no item in package.json for yarn lint or yarn typecheck. If there's something else I should do to check these files, let me know. I did run yarn build and yarn format, though since the TypeScript files are separate from the main code I'm not sure what else I should be looking for. 😄

[kof]

makes sense to me

[moshest]

lgtm

[kof]

merged, thanks

[kof]

Released in v10.6.0