codetools wrongly complains about lazy evaluation in S4 methods

Le 03/06/2023 ? 17:50, Mikael Jagan a ?crit :

In a package, I define a method for not-yet-generic function 'qr.X'
like so:

    > setOldClass("qr")
    > setMethod("qr.X", signature(qr = "qr"), function(qr, complete,

ncol) NULL)

The formals of the newly generic 'qr.X' are inherited from the
non-generic
function in the base namespace.  Notably, the inherited default value of
formal argument 'ncol' relies on lazy evaluation:

    > formals(qr.X)[["ncol"]]

    if (complete) nrow(R) else min(dim(R))

where 'R' must be defined in the body of any method that might
evaluate 'ncol'.
To my surprise, tools:::.check_code_usage_in_package() complains about
the
undefined symbol:

    qr.X: no visible binding for global variable 'R'
    qr.X,qr: no visible binding for global variable 'R'
    Undefined global functions or variables:
      R

I think this issue is similar to the complaints about non defined
variables in expressions involving non standard evaluation, e.g. column
names in a data frame which are used as unquoted symbols. One of
workarounds is simply to declare them somewhere in your code. In your
case, it could be something as simple as:

   R=NULL

Best,
Serguei.

I claim that it should _not_ complain, given that lazy evaluation is a
really
a feature of the language _and_ given that it already does not
complain about
the formals of functions that are not S4 methods.

Having said that, it is not obvious to me what in codetools would need
to change
here.  Any ideas?

I've attached a script that creates and installs a test package and
reproduces
the check output by calling tools:::.check_code_usage_in_package().
Hope it
gets through.

Mikael