I have a function which manipulates a ggplot object, by converting it to a grob and then modifying the layers. I would like the function to return a ggplot object not a grob
You can try the following:
p = ggplotify::as.ggplot(g)
For more info, see https://cran.r-project.org/web/packages/ggplotify/vignettes/ggplotify.html
It involves a little bit of a cheat annotation_custom(as.grob(plot),...), so it may not work for all circumstances: https://github.com/GuangchuangYu/ggplotify/blob/master/R/as-ggplot.R