A nested execution of functions with a custom decorator does not log functions name from separate module

Question

I have a sequence of nested function calls in my Typescript project. As Typescript does not support function level decorator, I wrote a customer decorator function to use with my functions.

(This is a sample scenario of files I am trying to sketch below to help you understand the structure of the actual project.)

decorator.ts:

const functionLoggingDecorator = (fn: Function) => 
    (...args: any) => {
        logger.info(`${fn.name} is called with args ${args}`);
        return fn(...args);
    }

Now, my functions are in different files.

file1.ts

const func1 = (a: number, b: number) => {
    const sumWithLoggingDecorator  = functionLoggingDecorator(sum);

    const mulWithLoggingDecorator  = functionLoggingDecorator(mul);

    return sumWithLoggingDecorator(a, b) + mulWithLoggingDecorator(a, b)
}

const mainDriver = (a: number, b: number) => {
    const withLoggingDecorator = functionLoggingDecorator(func1);
    return withLoggingDecorator(a, b)
}

mainDriver(5, 6);

sum.ts

const sum = (a: number, b: number) => a + b;

mul.ts

const mul = (a: number, b: number) => a * b;

So... when it is executing, I get the first log as

'func1 is called with args 5,6'

But then in the next logs, the name of the functions are missing. The logs are:

This is for the sum

' is called with args 5,6

and, this is for the mul

' is called with args 5,6'

What I found is, if I use the decorator with functions that are in the same module i.e. in the same file, the log has the function name. But if they are in a separate file as I mentioned above, I don't get the function name.

I am not entirely sure, henceforth, asking the question here.

Is it happening because of hoisting functions? As a result, the names are missing?

I know, with strict mode I can't use callee, caller, argument. I also tried fn.toString() then apply a regex to extract the function name. But did not work as I used the arrow function pattern.

I found another way with creating an Error stack object mentioned in this StackOverflow answer. But I am not confident if this should be used in production code and if stack.split('\n')[2].trim() mentioned in the answer is always true for all cases.

A nested execution of functions with a custom decorator does not log functions name from separate module

0 Answers0