T
tRPC

How to Type a Middleware factory?

How to Type a Middleware factory?

NNeoBean
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7/27/2023
Lemme first show you what I want, so you can get the gist of it. (Consider me less experienced in typescript) 
publicProcedure
    .input(z.object({ test: z.boolean() }))
    .use(middlewareFactory( /** TO GET INPUT TYPECHECKING HERE */ ))
publicProcedure
    .input(z.object({ test: z.boolean() }))
    .use(middlewareFactory( /** TO GET INPUT TYPECHECKING HERE */ ))
This is what I put together. This almost works 
/// types
type CustomPParams<T> = ProcedureParams<AnyRootConfig,unknown,unknown,T,unknown,unknown,unknown>
type MiddlewareFactory = <T>(input: T) => MiddlewareFunction<CustomPParams<T>, ProcedureParams>

/// a middleware factory
export const middlewareFactory: MiddlewareFactory = input => ({ next }) => { return next() }
/// types
type CustomPParams<T> = ProcedureParams<AnyRootConfig,unknown,unknown,T,unknown,unknown,unknown>
type MiddlewareFactory = <T>(input: T) => MiddlewareFunction<CustomPParams<T>, ProcedureParams>

/// a middleware factory
export const middlewareFactory: MiddlewareFactory = input => ({ next }) => { return next() }
I get autocompletion in vscode, but when I press tab and proceed with the autocompletion, I get an error that looks like this (the screenshot attached). Feels like i'm in the right path but cant exactly make a solid type out it. Now, for my very specific use case, i did make an workaround by making that T generic partial 
type MiddlewareFactory = <T>(input: Partial<T>) => MiddlewareFunction<CustomPParams<T>, ProcedureParams>
type MiddlewareFactory = <T>(input: Partial<T>) => MiddlewareFunction<CustomPParams<T>, ProcedureParams>
But this feels like a half measure. And provided that different validation libs might affect the type of input in subtle ways, I need to know how to properly type this thing. Thank you
No description
NNeoBean
View on Discord
7/28/2023
please expand this thread panel horizontally. easier to read without the code getting wrapped Well, ctx doesnt get typed in this way, look at this code 
type CustomPParams<T> = ProcedureParams<
    AnyRootConfig,
    MyCustomContext, /** PUTTING CONTEXT TYPE HERE DOESNT WORK */
    unknown,
    T,
    unknown,
    unknown,
    unknown
>
type CustomPParams<T> = ProcedureParams<
    AnyRootConfig,
    MyCustomContext, /** PUTTING CONTEXT TYPE HERE DOESNT WORK */
    unknown,
    T,
    unknown,
    unknown,
    unknown
>
I think I'm supposed to use t.middleware, this way I do get the context/meta types, but i cant seem to make a custom factory. Modifying above code like this throws an error 
export const middlewareFactory: MiddlewareFactory = input => t.middleware(({ next }) => { return next() })
export const middlewareFactory: MiddlewareFactory = input => t.middleware(({ next }) => { return next() })
MiddlewareBuilder is not assignable .. such and such

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How to Type a Middleware factory?

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