TTC
Theo's Typesafe Cult•3y ago
CuriouslyCory

Best practices - defining types when lib doesn't export the type

I'm writing a hook that wraps a transaction from another library. The library returns a Promise<SendTransactionResult>, but SendTransactoinResult is not exported from the library. I'm writing a handler for the promise but I'm struggling with what the best practice would be for defining the type that this callback should expect. 
 /*...inside hook...*/
// my function
const afterContractWrite = useCallback(
  (result: <HowWouldYouDefineThisType?>) => {
    onSettled?.();
    return result.wait();
  },
  [onSettled]
); 

//this method returns a Promise<SendTransactionResult> but the type is not exported from the lib so I can't just import it.
writeAsync?.() 
      .then(afterContractWrite)
 /*...inside hook...*/
// my function
const afterContractWrite = useCallback(
  (result: <HowWouldYouDefineThisType?>) => {
    onSettled?.();
    return result.wait();
  },
  [onSettled]
); 

//this method returns a Promise<SendTransactionResult> but the type is not exported from the lib so I can't just import it.
writeAsync?.() 
      .then(afterContractWrite)
How would you handle this?
3 Replies
CuriouslyCory
CuriouslyCoryOP•3y ago
I found Awaited<ReturnType<typeof writeAsync>>, but it's throwing a type error: 
Type '((overrideConfig?: { recklesslySetUnpreparedArgs?: undefined; recklesslySetUnpreparedOverrides?: (Overrides & { from?: `0x${string}` | undefined; }) | undefined; } | undefined) => Promise<...>) | undefined' does not satisfy the constraint '(...args: any) => any'.
  Type 'undefined' is not assignable to type '(...args: any) => any'.
Type '((overrideConfig?: { recklesslySetUnpreparedArgs?: undefined; recklesslySetUnpreparedOverrides?: (Overrides & { from?: `0x${string}` | undefined; }) | undefined; } | undefined) => Promise<...>) | undefined' does not satisfy the constraint '(...args: any) => any'.
  Type 'undefined' is not assignable to type '(...args: any) => any'.
So, writeAsync can either be a function, or undefined, and the type error is complaining that it can't infer the return type of undefined since it's not a function. Any suggestions on how I would gate that so I can get the result assuming it's not undefined?
Unknown User
Unknown User•3y ago
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CuriouslyCory
CuriouslyCoryOP•3y ago
Thanks! I'll give this a shot.

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