Migrating old package structure to box module

[mpettis]

I have an old package with the classic package structure of one function in one file. So in the below, mymod is a directory containing the R files from the old package. I'd like to access the functions in the file with a syntax like: mymod$fun1(). Is there a way to use box::use() to make that happen? Below is an example of my code layout.

.
|-- R
|   `-- tryBox.R
|-- box-pkg-demo.Rproj
`-- mymod
|   |-- fun1.R
    `-- fun2.R

Thank you

[klmr]

If I understand you correctly, you want to “pool” all the functions defined in the files under mymod inside a single module, correct?

There’s a Stack Overflow question asking something quite similar.

The solution is to add a __init__.R file under mymod which imports and exports the submodules:

# mymod/__init__.R:

#' @export
box::use(
  ./fun1[...],
  ./fun2[...],
)

Afterwards, importing mymod will make all exported objects from the nested modules (= the source files) available.

Now you can use it in R/tryBox.R, for example:

box::use(../mymod)

mymod$fun1()

Note the relative import (../mymod).

[mpettis]

Got it. I did not see this SO answer, but I was trying to figure it out via the __init__.R statements. Now this is clearer, and makes sense. Thanks!

[mpettis]

Also, I assume I'll have to explicitly list them in __init__.R... There's no way to just slurp in the whole directory of files and do that, assuming all the R files in there are of the same form and for the same use? I assume it is probably bad implicit-vs-explicit coding form, but was just curious...

[klmr]

There's no way to just slurp in the whole directory of files and do that …?

I’m afraid not: ‘box’ intentionally does not allow dynamic box::use() statements, because the idea is to treat them as static code, which would in principle be amenable to static analysis down the line.

… but we can cheat. This isn’t pretty, but putting the following in mymod/__init__.R works:

.on_load = function (ns) {
    submodule_files = grep(
        '^__init__\\.[rR]$',
        dir(box::file(), pattern = '\\.[rR]$'),
        value = TRUE,
        invert = TRUE
    )
    module_raw_names = sub('\\.[rR]$', '', submodule_files)
    module_declarations = lapply(
        module_raw_names,
        \(mod) bquote(. / .(as.name(mod))[...])
    )

    do.call(box::use, module_declarations, envir = ns)

    import_env = parent.env(ns)
    do.call(box::export, lapply(ls(import_env), as.name))
}

# Necessary to declare this as a non-legacy mdoule, and ensure that the `.on_load` hook is run.
box::export()

[mpettis]

Wow, thanks! I may try if I get problems maintaining synchronization between __init__.R and the constituent files. I intend to stay clean and hygenic until I'm overwhelmed, then I'll use this.