Type pattern for partial classes override

When using makeStyles with Typescript, it requires all styles as follows:

Argument of type '{ root: { minWidth: number; }; }' is not assignable to parameter of type 'Styles<Theme, {}, ButtonClassKey>'.
  Type '{ root: { minWidth: number; }; }' is missing the following properties from type 'Record<ButtonClassKey, CSSProperties | ((props: {}) => CSSProperties)>': label, text, textPrimary, textSecondary, and 12 more.ts(2345)

In my understanding, only the styles I want can be provided.

• This is not a v0.x issue.
• I have searched the issues of this repository and believe that this is not a duplicate.

Expected Behavior 🤔

No type error occurs.

Current Behavior 😯

Type error occurs.

Steps to Reproduce 🕹

Context 🔦

Your Environment 🌎

Tech	Version
Material-UI	4.0.0-rc.0
React	16.8.6
TypeScript	3.4.5

[stephenh]

It really comes down to someone contributing this change and then seeing how our test suite reacts to it.

Cool! I’ll see if my itch persists and try it out if I get a chance.

[stephenh]

@eps1lon so, I’m not really following; @takakobem and I want to do the same thing, of purposefully restricting our styles def to known-good class keys, i.e. your comment here:

As soon as you would declare a class key that isn’t in the styles of the Button you would get an error anyway when you end up with <Button classes={useStyles()} />

Ah, okay, I see, you’re right; FWIW I’m using createStyles via the withStyles HOC, which doesn’t catch that:

// useStyles has an invalid class key in it
export const MyButton = withStyles(useStyles)(Button);

Granted, it looks like withStyles has some anys in it and HOC’s in general are a pita to get types right, hence why I wanted/expected to do the enforcement on the createStyles side…

I guess also, why not change createStyles to take the a Partial, or is the idea that that would break some of the type inference that is currently happening for the classes={useStyles()} usage?

If it would, then it makes sense to keep as-is since a majority of use cases do what it inferred. I didn’t realize the classes={useStyles()} would catch this.