geom_qq_line() issues warning since #4866

[capnrefsmmat]

Consider the first example on the geom_qq documentation page:

df <- data.frame(y = rt(200, df = 5))
p <- ggplot(df, aes(sample = y))
p + stat_qq() + stat_qq_line()

In the released version of ggplot2, this issues no warning. On the v3.4.0-rc branch, this produces the warning

Warning message:
The following aesthetics were dropped during statistical transformation: sample
ℹ This can happen when ggplot fails to infer the correct grouping structure in the data.
ℹ Did you forget to specify a `group` aesthetic or to convert a numerical variable into a
  factor? 

Removing stat_qq_line() eliminates the warning. I believe this is due to #4866. I believe the warning is spurious, since no grouping aesthetics are necessary here.

[clauswilke]

Thanks for pointing this out.

@thomasp85 We should fix this before the 3.4.0 release. It's a simple dropped_aes = "sample" inserted somewhere here:

ggplot2/R/stat-qq-line.R

Lines 47 to 49 in a58b48c

	default_aes = aes(x = after_stat(x), y = after_stat(y)),
	required_aes = c("sample"),

[thomasp85]

Thanks - there have been one more of these already with weight and stat_count()... will fix this in the rc-branch