Callback to promise

callback-to-promise.ts

function make_wrapper<T extends { [k: string]: any }>(root: T) {
    type VHWithoutLastElement<T extends [...args: any]> = T extends [...args: infer P, last: any] ? P : never;
    type VHLastElement<T extends [...args: any]> = T extends [...args: any, last: infer LastType] ? LastType : never;
    type VHCallbackExtractValue<T extends any> = T extends ((err: any, value: infer ValueType) => void) ? (ValueType extends unknown ? void : ValueType) : never;
    type VHPromisifier<T extends (...args: any) => any> = T extends (...args: infer P) => any ? ((...args: VHWithoutLastElement<P>) => Promise<VHCallbackExtractValue<VHLastElement<P>>>) : never;
    return <fn_t extends keyof T>(fn: fn_t): VHPromisifier<T[fn_t]> => {
        return promisify(root[fn]).bind(root);
    };
}

const pm2_ = make_wrapper(pm2);
await pm2_('connect')()