Add intercept to list of known y aesthetics (#4434)

Author: thomasp85

NEWS.md

@@ -1,5 +1,8 @@
 # ggplot2 (development version)
 
+* Fix a bug in `geom_abline()` that resulted in `intercept` not being subjected
+  to the transformation of the y scale (@thomasp85, #3741)
+
 * Fix bug in `guide_coloursteps()` that would repeat the terminal bins if the
   breaks coincided with the limits of the scale (@thomasp85, #4019)
 

R/ggplot-global.R

@@ -20,7 +20,8 @@ ggplot_global$element_tree <- list()
   "colour", "fg", "fill", "group", "hjust", "label", "linetype", "lower",
   "lty", "lwd", "max", "middle", "min", "pch", "radius", "sample", "shape",
   "size", "srt", "upper", "vjust", "weight", "width", "x", "xend", "xmax",
-  "xmin", "xintercept", "y", "yend", "ymax", "ymin", "yintercept", "z"
+  "xmin", "xintercept", "y", "yend", "ymax", "ymin", "yintercept", "z",
+  "intercept"
 )
 
 ggplot_global$all_aesthetics <- .all_aesthetics
@@ -49,4 +50,4 @@ ggplot_global$x_aes <- c("x", "xmin", "xmax", "xend", "xintercept",
   "xmin_final", "xmax_final", "xlower", "xmiddle", "xupper", "x0")
 
 ggplot_global$y_aes <- c("y", "ymin", "ymax", "yend", "yintercept", "ymin_final",
-  "ymax_final", "lower", "middle", "upper", "y0")
+  "ymax_final", "lower", "middle", "upper", "y0", "intercept")