使用 Firebase 可调用函数使用 TypeScript 进行类型检查

Question

I am using TypeScript to write callable Cloud Functions with Firebase, and it is important that I receive data of a certain type.

My function declaration is as follows:

export const questionnaireSubmit = https.onCall(async (data: questionnaireDoc): Promise<apiOut> => {})

Because I defined questionnaireDoc as an interface, using data instanceof questionnaireDoc gives the following error in my IDE:

'questionnaireDoc' only refers to a type, but is being used as a value here.ts(2693)

When calling this function in a TypeScript program, I can use the HttpsCallable<parameterType,returnType> type from "firebase/functions" to define its input type, but this relies on the client code explicitly setting the type and using a language that supports explicit types.

Right now, I am checking the existence of necessary properties using the following within my cloud function:

        switch (undefined) {
            case <unknown>data.property1:
            case <unknown>data.property2:
            case <unknown>data.property3:
            case <unknown>data.property4:
            case <unknown>data.property5:
            case <unknown>data.property6:
            case <unknown>data.property7:
            case <unknown>data.property8:
            case <unknown>data.property9:
                throw new https.HttpsError("invalid-argument", "Missing required field(s)");
        }

But this workaround does not seem necessary or scalable.

What is the best practice to ensure inputs passed to Firebase Callable functions are correct within the function using TypeScript?

Thanks!

Answer 1

The onCall function is generic and can take both a request and a return type. I think this might help:

export const questionnaireSubmit = 
  https.onCall<questionnaireDoc,apiOut>(async (data) => {
    // ...
  })