gganimate doesn't correctly render text in expression()

[moondog1969]

Plotmath text with expression() is not working on axes in animations. For instance, the 2 is not super-scripted for the equation on the y-axis label in the plot below.

library(gganimate)

ggplot(mtcars, aes(mpg, disp)) +
  geom_point(aes(color = gear)) +
  transition_states(gear, transition_length = 2, state_length = 1) +
  enter_fade() +
  ylab(expression(E = mc^2)) +
  exit_fade()

I'm using:

R version 4.4.2 (2024-10-31 ucrt)
Platform: x86_64-w64-mingw32/x64
Running under: Windows 10 x64 (build 17134)

gganimate version: 1.0.9.

This seems to be a new issue, as gganimate axes were using expression() correctly until recently.

Thanks

[moondog1969]

Will work correctly using bquote() instead of expression():

e <- bquote(E == mc^2)

ggplot(mtcars, aes(mpg, disp)) +
  geom_point(aes(color = gear)) +
  transition_states(gear, transition_length = 2, state_length = 1) +
  enter_fade() +
  ylab(e) +
  exit_fade()