legend key does not respect `scale_fill_manual(..., drop = FALSE)`

[davidhodge931]

In the below example, the legend key for female should be red with a black border.

I'm using the latest DEV version of ggplot2. It works correctly in 3.4.4.

library(tidyverse)
library(palmerpenguins)

penguins |>
  mutate(sex = factor(sex)) |>
  filter(sex == "male") |>
  ggplot() +
  geom_violin(aes(
    x = sex,
    y = body_mass_g,
    fill = sex,
  )) +
  scale_fill_manual(values = c("red", "blue"), drop = FALSE)

^{Created on 2023-12-15 with reprex v2.0.2}

[thomasp85]

This is due to a new feature where layers only contribute legends to the data that is shown in the layer. You can reinstate the old behaviour by setting show.legend = TRUE in the layer

[teunbrand]

Yeah this is intended behaviour from #5502, which you can indeed revert by using show.legend as Thomas says.