{ggplot2} theme_set() with {targets} and crew_controller_local()

[gregrs-uk]

Thanks for creating this package, which I'm hoping to use alongside the excellent {targets} package to speed up some pipelines.

I'm having difficulty setting a global {ggplot2} theme when using crew_controller_local. I've attached a MWE _targets.R below. When the controller option is commented out, the theme is correctly set. When crew_controller_local is used, it's not.

I assume this might be something to do with the ggplot_global environment used within ggplot2::theme_set().

I tried setting reset_globals = FALSE in the crew_controller_local call but this didn't help. Do you have any suggestions that would allow this to work?

(By the way, I'm using the version from the current main branch on Github: 87f4824.)

library(targets)
library(crew)
library(ggplot2)

tar_option_set(
  # controller = crew_controller_local()
)

theme_set(theme_dark())

list(
  tar_target(
    plot_file,
    ggsave(
      "plot.png",
      ggplot(iris, aes(Sepal.Width, Sepal.Length)) + geom_point()
    ),
    format = "file"
  )
)

[wlandau]

I think this is because ggplot2::theme_set() sets the theme in a local package environment inside ggplot2 instead the environment that targets ships to the workers (tar_option_get("envir"), which is usually .GlobalEnv).

> ggplot2::theme_set
function (new) 
{
    old <- ggplot_global$theme_current
    ggplot_global$theme_current <- new
    invisible(old)
}

On each worker, ggplot2 is loaded from scratch and does not know the modifications to the ggplot_global object hidden inside the ggplot2 package environment. As an alternative, you could encapsulate theme_set() inside a global function and then call it in each ggplot target.

library(targets)
library(crew)
library(ggplot2)

tar_option_set(
   controller = crew_controller_local()
)

set_theme <- function() {
  theme_set(theme_dark())
}

list(
  tar_target(
    name = plot_file,
    command = {
      set_theme()
      ggsave(
        "plot.png",
        ggplot(iris, aes(Sepal.Width, Sepal.Length)) + geom_point()
      )
    },
    format = "file"
  )
)

If you have many such targets, then tarchetypes::tar_hook_before() could make this process convenient.

[gregrs-uk]

Brilliant, thanks. tarchetypes::tar_hook_before() has done the job nicely.