ESlint error, Type '() => Promise<void>' is missing the following properties from type 'Promise<void>': then, catch, [Symbol.toStringTag], finally

Question

I'm getting an error that I can only fix with adding any as the return value.

export const dbConnections: any = {};

export const connectDb: Promise<void> = async () => {
    if (dbConnections.isConnected) {
        return;
    }

    try {
        const db = await mongoose.connect(config.get('mongoURI'), {
            useNewUrlParser: true,
            useUnifiedTopology: true,
            useFindAndModify: false,
            useCreateIndex: true,
        });

        dbConnections.isConnected = db.connections[0].readyState;
    } catch (err) {
        createError('Error caught connecting to db!', err);
    }
};

This throws an error,

export const connectDb: Promise<void> = async () => {
                                        ^^^^^^^^^^^^^
Type '() => Promise<void>' is missing the following properties
  from type 'Promise<void>': then, catch, [Symbol.toStringTag], finally

If I do any instead of Promise<void>, then the error disappears, but that's obviously not how I'm trying to go about this. How can I fix this lint error?

Answer 1

Issue is in function declaration. You need to give the return type as Promise<void>.

export const connectDb = async (): Promise<void> => {
    if (dbConnections.isConnected) {
        return;
    }

    try {
        const db = await mongoose.connect(config.get('mongoURI'), {
            useNewUrlParser: true,
            useUnifiedTopology: true,
            useFindAndModify: false,
            useCreateIndex: true,
        });

        dbConnections.isConnected = db.connections[0].readyState;
    } catch (err) {
        createError('Error caught connecting to db!', err);
    }
};

Answer 2

Asynchronous functions in typescript return promise value.

like this:

export const dbConnections: any = {};

export const connectDb: () => Promise<void> = async () => {
    ...
};