TS misunderstands types

[babakfp]

Hi

export type Config = {
    presets?: {
        /** @default false */
        flexGrid?: boolean
        /** @default false */
        fontWeightRegular?: boolean
        /** @default true */
        moreDefaultValues?: boolean
        /** @default false */
        screenToDynamicScreen?: boolean
    }
    utilities?: {
        /** @default true */
        bgGrid?: boolean
        /** @default true */
        bgRadial?: boolean
        /** @default true */
        dir?: boolean
        /** @default true */
        drag?: boolean
        /** @default true */
        flip?: boolean
        /** @default true */
        hideShow?: boolean
        /** @default true */
        inputResets?: boolean
        /** @default true */
        insetCenter?: boolean
        /** @default true */
        overflowUnset?: boolean
        /** @default true */
        tapHighlight?: boolean
    }
    variants?: {
        /** @default true */
        notVariants?: boolean
    }
}

const defaultConfig = {
    presets: {
        flexGrid: false,
        fontWeightRegular: false,
        moreDefaultValues: true,
        screenToDynamicScreen: false,
    },
    utilities: {
        bgGrid: true,
        bgRadial: true,
        dir: true,
        drag: true,
        flip: true,
        hideShow: true,
        inputResets: true,
        insetCenter: true,
        overflowUnset: true,
        tapHighlight: true,
    },
    variants: {
        notVariants: true,
    },
} satisfies Config

export default (userConfig?: Config) => {
    const config = merge(defaultConfig, userConfig || {})
}

The issue is, TS shows me this error, for example, fontWeightRegular in config.presets?.fontWeightRegular can be undefined.

It's expected that fontWeightRegular will always have a value. But TS doesn't know that.

I want to merge the default options with the same options (with custom values) added by the user.

[voodoocreation]

Hey! This appears to be a duplicate of issues #28 and #30 - it's a known gap in the type inferring that's provided within this package, but I haven't been able to rewrite it in a way where TS is able to be more aware of what the value will be based on the order of events within the unlimited objects and recursion that's going on within the runtime code, which is why it can results in a union of all possible values (which will include undefined if that's a possible value with what's being passed in). Though your declared Config type won't be helping things, as you've marked everything as being optional, which will result in everything being possibly undefined. A lot of the type inferring that this package does won't be doing too much due to your example working with declared types rather than inferring based on the runtime declaration.

What I would suggest is to declare your Config type with all properties that you know will always be defined without marking them as optional with ?, then for your function parameter, assign the parameter userConfig?: Partial<Config> (or DeepPartial if using utility-types), then you can just assign the return type as Config which is more accurate for what you're trying to achieve.

More context is available in issues #28 and #30 though, and PRs are always welcome if you'd like to try and improve the type inferring.

[babakfp]

Thanks.