geom_hline() and geom_vline() overwrite provided data frame

[dariyasydykova]

This comes from a discussion with @clauswilke. The issue here is related to #2950 but somewhat different.

When a data frame is provided to geom_hline(), it is overwritten. The problem seems to be in the following code chunk:

ggplot2/R/geom-hline.r

Lines 12 to 17 in 3c3062d

	# Act like an annotation
	if (!missing(yintercept)) {
	data <- new_data_frame(list(yintercept = yintercept))
	mapping <- aes(yintercept = yintercept)
	show.legend <- FALSE
	}

Here is a reprex to demonstrate this issue:

This works as expected

library(ggplot2)
library(tidyr)

d <- data.frame(c = c("a", "b"),
                y = c(1, 3))

d %>% ggplot() +
  geom_hline(data = d, aes(yintercept = y, color = c)) +
  facet_wrap(~c)

This doesn't work as expected. The provided data frame is dropped, and colors aren't mapped.

d %>% ggplot() +
  geom_hline(data = d, aes(color = c), yintercept = 1) +
  facet_wrap(~c)

^{Created on 2019-01-19 by the reprex package (v0.2.1)}

No warning is given when the original data frame is being overwritten.

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