Summary

In R, the return statement is not strictly required in functions.

# this returns NULL
gives_nothing <- function(x, y){
    print(x)
    print(y)
}

# this returns the value of n
gives_sum <- function(x, y){
    n <- x + y
    n
}

This means that it can sometimes be difficult to understand, from looking at the code, what a function will return.

How to close this issue

To close this issue, make sure that every function in the R package is explicitly using a return statement. The R package's code can all be found in R-package/R.

For functions which look like they should not return anything, please add a new statement at the end:

    return(invisible(NULL))

How this improves LightGBM

This fix will make the R package a little bit more explicit, reducing the risk of mistakes during future development.