Add error to `direction` argument of guide_*()

[charliejhadley]

The direction argument of guide_*() functions can only be "horizontal" or "vertical". At present an unhelpful error message is returned in case of error:

library("ggplot2")

ggplot(quakes,
       aes(x = long,
           y = lat,
           colour = mag)) +
  geom_point() +
  guides(colour = guide_colorbar(direction = "horiz"))
#> Error in if (!g$title.position %in% c("top", "bottom", "left", "right")) {: argument is of length zero

In line with the tidyverse style guide an error like this would be more suitable:

library("ggplot2")

ggplot(quakes,
       aes(x = long,
           y = lat,
           colour = mag)) +
  geom_point() +
  guides(colour = guide_colorbar(direction = "horiz"))
#> Error: The direction argument of guide_colorbar() must be either "vertical" or "horizontal"  

[teunbrand]

Thanks, that is indeed an inelegant error message. After #4879 gets merged, this will return the following error message:

Error in guide_colorbar():
! direction must be one of "horizontal" or
"vertical", not "horiz".
ℹ Did you mean "horizontal"?