Should dir_walk have a glob argument?

[cboettig]

It's not obvious to me why dir_walk and dir_map lack the glob and pattern argument present in the other list functions (dir_ls() and friends).

For example, I'd like to have travis check if all Rmds can render in a given git repo.

Something like:

fs::dir_walk(glob = "*.Rmd", fun = rmarkdown::render,  recursive = TRUE)

seems like a nice alternative to:

lapply(list.files(pattern = ".*.Rmd", recursive = TRUE, full.names = TRUE), rmarkdown::render)

In general, I can imagine many other scenarios where I'd want to walk a directory for it's side effect based on a globbing pattern. Maybe I'm just failing to understand the logic of dir_walk and dir_map, but they seem like attractive alternatives to piping dir_ls() version into a purrr function (and thus introducing a purrr dependency).

[jimhester]

The implementation doesn't really make this easy to do, the mapping is done in C++, so there is no (easy) way to match against a glob or regex pattern without adding a dependency to a regex library.

You can always do the filtering in the function, e.g.

render_rmd <- function(file) {
  if (endsWith(file, ".Rmd")) {
    rmarkdown::render(file)
  }
}

fs::dir_walk(fun = render_rmd, recursive = TRUE)

[cboettig]

thanks, that makes sense; if it's not in the C++. The filtering approach is nice (though I was hoping for a one-liner for my .travis.yml).

[jimhester]

fs::dir_walk(fun = function(f) if (endsWith(f, ".Rmd")) rmarkdown::render(file), recursive = TRUE)

😉