geom_raster drops legend when col and fill aesthetics added

[davidhodge931]

legend works with geom_tile when col then fill aesthetics added

library(tidyverse)

#legend works with geom_tile
ggplot2::faithfuld |>
  head(10) |> 
  ggplot() +
  geom_tile(aes(x = waiting, y = eruptions, col = density, fill = density)) 

legend does not work with geom_raster when col then fill aesthetics added

#legend does not work with geom_raster
ggplot2::faithfuld |>
  head(10) |> 
  ggplot() +
  geom_raster(aes(x = waiting, y = eruptions, col = density, fill = density))
#> Warning in geom_raster(aes(x = waiting, y = eruptions, col = density, fill =
#> density)): Ignoring unknown aesthetics: colour

^{Created on 2023-06-15 with reprex v2.0.2}

[davidhodge931]

Works if the order of aesthetics is fill then col, but not the other way around

library(tidyverse)

#legend works if aesthetic order is fill then col
ggplot2::faithfuld |>
  head(10) |>
  ggplot() +
  geom_raster(aes(x = waiting, y = eruptions, fill = density, col = density))
#> Warning in geom_raster(aes(x = waiting, y = eruptions, fill = density, col =
#> density)): Ignoring unknown aesthetics: colour

^{Created on 2023-06-15 with reprex v2.0.2}

[teunbrand]

Good catch! From some brief experimentation, it seems to be dropped due to the legend key data having colour as the aesthetics name after merging fill and colour guides, which then is discarded by the guide_geom()/GuideColourbar$get_layer_key(). I think this should be fixed in the guide_merge()/GuideColourbar$merge() step.