`annotate()` with hline and vline geoms

[mikkmart]

I was adding other annotations to a plot, and wanted to add reference lines. I was in the mindset of annotate()ing thigs, so I tried to use it with "hline" and "vline", but discovered that nothing happened. For example:

library(ggplot2)

p <- ggplot(data.frame(x = 1, y = 1), aes(x, y)) + geom_point()

p +
  annotate("hline", yintercept = 0) +
  annotate("vline", xintercept = 0)

What I expected:

p +
  annotate("segment", x = -Inf, xend = Inf, y = 0, yend = 0) +
  annotate("segment", x = 0, xend = 0, y = -Inf, yend = Inf)

I realize the “solution” here is to use the geoms directly with fixed values:

p +
  geom_hline(yintercept = 0) +
  geom_vline(xintercept = 0)

But annotate() not working seems like an unexpected inconsistency.

[smouksassi]

dup of #1052

[mikkmart]

Thanks @smouksassi, I didn't think to look that far back. If this is indeed expected behaviour, perhaps a documentation patch would be in order? I could prepare something.

[mikkmart]

And/or, indeed, a warning if "abline", "hline" or "vline" are passed to annotate() as the geom, with instructions to use the corresponding geom directly.

[mikkmart]

(Also a duplicate of #2011. I should definitely have included "hline" in my initial search, rather than just "annotate".)