Get and check aes params

[skaltman]

It would be useful to be able to check for aesthetic parameters (i.e., aesthetics that have been set and not mapped), such as fill = "blue":

library(ggcheck)
library(ggplot2)

p <-
  ggplot(mpg, aes(manufacturer)) +
  geom_bar(fill = "blue", width = 0.5)

^{Created on 2021-11-16 by the reprex package (v2.0.1)}

uses_geom_param() checks "geom params", (binwidth, etc.), but not "aes params" (fill = "blue"):

uses_geom_param(p, "bar", params = list(fill = "blue"))
#> Error in uses_geom_param(p, "bar", params = list(fill = "blue")): Grading error: the supplied parameters 'fill' are invalid.
uses_geom_param(p, "bar", params = list(width = 0.5))
#> [1] TRUE

It would also be nice to be able to easily get aes params. You can do:

get_geom_layer(p, geom = "bar")$layer$aes_params
#> $fill
#> [1] "blue"

but it would be nice to have a function.

[rossellhayes]

Would you envision this as one function that can check both geom params and aes params, like uses_geom_param(p, "bar", params = list(fill = "blue")), or a new function to check aes params, like uses_aes_param()?

[skaltman]

I think it would be easier if it was one function, but it does mess with the naming convention a bit since fill is not technically a geom param.

It would also be nice if the function used ... so you don't have to put the parameters in a list (like what you did with the labels functions).

[rossellhayes]

Looking at the documentation, it seems that the function is already a bit overloaded. It currently checks for geom_params and stat_params, so I don't think adding aes_params would cause much issue.

[rossellhayes]

@skaltman Currently, uses_labels() returns a named vector if you check more than one label. uses_geom_params() returns a single logical value indicating if all params match. Should uses_geom_params() return a named vector as well?

library(ggcheck)
library(ggplot2)

p <- ggplot(mpg, aes(x = manufacturer, y = hwy)) +
  geom_boxplot(width = 0.5, na.rm = TRUE) +
  labs(x = "Manufacturer", y = "MPG")

uses_labels(p, x = "Manufacturer", y = "MPG")
#>    x    y 
#> TRUE TRUE
uses_geom_param(p, "boxplot", width = 0.5, na.rm = TRUE)
#> [1] TRUE

^{Created on 2021-11-30 by the reprex package (v2.0.1)}

[skaltman]

@rossellhayes Yeah, I think a named vector would work well. It seems like it would be good if both functions worked similarly. And if uses_geom_param() returns a named vector, you can check where exactly the student code went wrong without writing multiple calls to uses_geom_param().

[rossellhayes]

@skaltman Thank you! The PR should now be ready to go, let me know how it looks!