"stage()" does not work properly when prefixed with "ggplot2::"

[HMU-WH]

When I use a function from ggplot2 in my own R package, I need to prefix it with "ggplot2::". I found that, in this case, "stage()" does not work properly!

Here is the code to reproduce the bug:
This is the original example in ggplot2. I just changed "stage" to "ggplot2::stage".

ggplot(mpg, aes(class, displ)) +
  geom_violin() +
  stat_summary(
    aes(
      y = ggplot2::stage(displ, after_stat = 8),
      label = after_stat(paste(mean, "±", sd))
    ),
    geom = "text",
    fun.data = ~ round(data.frame(mean = mean(.x), sd = sd(.x)), 2)
  )

Throws the following error：

Error in `stat_summary()`:
! Problem while mapping stat to aesthetics.
ℹ Error occurred in the 2nd layer.
Caused by error:
! object 'displ' not found

[yutannihilation]

I need to prefix it with "ggplot2::"

While I agree ggplot2::stage() should work, I think you can import it to avoid the "Undefined global functions or variables" warnings.

#' @importFrom ggplot2 stage

[HMU-WH]

I need to prefix it with "ggplot2::"

While I agree ggplot2::stage() should work, I think you can import it to avoid the "Undefined global functions or variables" warnings.

#' @importFrom ggplot2 stage

I agree with your suggestion, but I still hope that ggplot2::stage() can work properly, because according to the R language specification, this should not cause an error. After all, this is not a symbolic function.

[teunbrand]

I think what is happening is that the stage() function is masked here to evaluate the after_stat component, but this masking doesn't work due to the ggplot2::-prefix, which uses the original unmasked stage() and thus evaluates the wrong component. I'm not sure yet what would be the best way to fix this.

[HMU-WH]

I think what is happening is that the stage() function is masked here to evaluate the after_stat component, but this masking doesn't work due to the ggplot2::-prefix, which uses the original unmasked stage() and thus evaluates the wrong component. I'm not sure yet what would be the best way to fix this.

Sorry, with my current ability, I am not capable of understanding the source code you pointed out in a short period of time.

However, it can be confirmed that there are indeed some flaws in the evaluation operation of the stage( ) function.

In addition to the issues I mentioned earlier, I have also noticed the following situations:

library(ggplot2)
library(patchwork)

by <- "cut"
p <- ggplot(diamonds, aes(x = cut, y = price))

p1 <- p + geom_violin(aes(colour = .data[[by]], fill = after_scale(color)), trim = FALSE)
p2 <- p + geom_violin(aes(colour = .data[[by]], fill = stage(!!sym(by), after_scale = color)), trim = FALSE)
p3 <- p + geom_violin(aes(colour = .data[[by]], fill = stage(.data[[by]], after_scale = color)), trim = FALSE)

p1 | p2 | p3

The legend of "P3" is inconsistent with "P1" and "P2". Of course, I understand that it can be corrected using p3 + labs(fill = by), but in my opinion, these three methods should produce the same image.

[teunbrand]

I have also noticed the following situations:

This particular situation should already be fixed in the current development version of ggplot2.

[yutannihilation]

To be comprehensive, I think we have three options about the level of fix.

1. Not fix. We can say, for example, after_scale() is a syntax rather than a usual function, so qualified form (ggplot2::) is not intended. cf. tidyselect didn't even export where() for a long time (Export where() r-lib/tidyselect#201).
2. Fix only ggplot2::.
3. Fix all cases including when stage() is re-exported.

I'd vote for 3 or 1. So, I like #6107 more because the approach of #6108 probably cannot handle the re-export cases.

[teunbrand]

Yeah you make a good point. So if we want this:

library(ggplot2)

ggplot(mpg, aes(displ, hwy)) +
  geom_point(
    aes(fill = stage(drv, after_scale = alpha(fill, 0.3))),
    shape = 21
  )

We cannot do.call() or otherwise construct stage(). Note that the points are not transparent.

ggplot(mpg, aes(displ, hwy)) +
  geom_point(
    aes(fill = do.call("stage", list(start = drv, after_scale = quote(alpha(fill, 0.5))))),
    shape = 21
  ) +
  labs(fill = "drv")

Nor can we use stage wrappers. Again, points are not transparent.

restage <- function(...) stage(...)

ggplot(mpg, aes(displ, hwy)) +
  geom_point(
    aes(fill = restage(drv, after_scale = alpha(fill, 0.3))),
    shape = 21
  ) +
  labs(fill = "drv")

^{Created on 2024-09-16 with reprex v2.1.1}

[thomasp85]

I personally holds the position that stage(), after_stat(), the old stat(), etc are all decorators, more than actual functions, that instructs aes() how to interpret the mapping.

I know this is a distinction we cannot necessary expect the users to know or understand, but I do think we can make a case for not allowing alternate call constructions

[teunbrand]

I don't think that is unreasonable. But if these are just syntax instead of functions, then I think the following should also work:

ggplot2::ggplot(ggplot2::mpg, ggplot2::aes(displ, hwy)) +
  ggplot2::geom_point(
    ggplot2::aes(fill = stage(drv, after_scale = scales::alpha(fill, 0.3))),
    shape = 21
  )
#> Error in `ggplot2::geom_point()`:
#> ! Problem while computing aesthetics.
#> ℹ Error occurred in the 1st layer.
#> Caused by error in `stage()`:
#> ! could not find function "stage"

^{Created on 2024-09-16 with reprex v2.1.1}

[thomasp85]

That I agree on

[yutannihilation]

Sorry for replying late. While I support @thomasp85's argument, I was thinking about the consistency with the rest of tidyverse. As dplyr allows using these special syntax with dplyr::, it might be a bit confusing if ggplot2 doesn't allow ggplot2::. (My personal preference is not to allow either dplyr:: or ggplot2::, but probably it's a bit too late).

data.frame(x = 1) |> 
  dplyr::select(dplyr::everything())
#>   x
#> 1 1

^{Created on 2024-09-23 with reprex v2.1.1}