如何缩小来自 Firebase Cloud Function 的 HttpsError？

Question

I have an onCall Firebase Cloud Function named getZohoDeskTicketById that throws an error like this:

throw new functions.https.HttpsError(
      'unknown',
      error.response.data.errorCode,
      error.response.data
);

And I am calling it like this:

import { httpsCallable, FunctionsError } from 'firebase/functions';    
// ...
const getZohoDeskTicketById = httpsCallable(functions, 'getZohoDeskTicketById');
const handleClick = async () => {
  try {
    const result = await getZohoDeskTicketById({
      ticketId: '345112301899997',
    });
    console.log(result);
  } catch (error) {
    if (error instanceof FunctionsError) { // TypeScript warning here
      console.log(error.code); // TypeScript warning here
      console.log(error.message); // TypeScript warning here
      console.log(error.details); // TypeScript warning here
    }
  }
};

But I'm having trouble with narrowing down the catch .

FunctionsError has a TypeScript warning of 'FunctionsError' only refers to a type, but is being used as a value here. ts(2693) 'FunctionsError' only refers to a type, but is being used as a value here. ts(2693)

and

error on each of my console.log's has a TypeScript warning of Object is of type 'unknown'.ts(2571)

So what is the correct way of narrowing down this error?

Answer 1

I created a user-defined type guard like so:

function isFunctionsError(error: unknown): error is FunctionsError {
  return (error as FunctionsError).details !== undefined;
}

const handleClick = async () => {
  try {
    const result = await getZohoDeskTicketById({
      ticketId: '345112301899997',
    });
    console.log(result);
  } catch (error) {
    if (isFunctionsError(error)) {
      console.log(error.code);
      console.log(error.message);
      console.log(error.details);
    }
  }
};

But if anyone knows of a better way, please post it!