Convert linetype NAs to blank lines

NEWS.md

@@ -1,5 +1,7 @@
 # ggplot2 (development version)
 
+* `linetype = NA` is now interpreted to mean 'no line' instead of raising errors
+  (@teunbrand, #6269).
 * New parameters for `geom_label()` (@teunbrand and @steveharoz, #5365):
   * The `linewidth` aesthetic is now applied and replaces the `label.size` 
     argument.

R/legend-draw.R

@@ -199,8 +199,6 @@ draw_key_crossbar <- function(data, params, size) {
 draw_key_path <- function(data, params, size) {
   if (is.null(data$linetype)) {
     data$linetype <- 0
-  } else {
-    data$linetype[is.na(data$linetype)] <- 0
   }
   grob <- segmentsGrob(0.1, 0.5, 0.9, 0.5,
     gp = gg_par(
@@ -388,8 +386,6 @@ draw_key_vline <- function(data, params, size) {
 draw_key_timeseries <- function(data, params, size) {
   if (is.null(data$linetype)) {
     data$linetype <- 0
-  } else {
-    data$linetype[is.na(data$linetype)] <- 0
   }
 
   grid::linesGrob(

R/scale-linetype.R

@@ -7,8 +7,15 @@
 #'
 #' @inheritParams discrete_scale
 #' @inheritDotParams discrete_scale -expand -position -na.value -scale_name -palette
-#' @param na.value The linetype to use for `NA` values.
 #' @rdname scale_linetype
+#' @details
+#' Lines can be referred to by number, name or hex code. Contrary to base R
+#' graphics, `NA`s are interpreted as blanks.
+#'
+#' \if{html}{\figure{linetype_table.svg}{Named linetypes by number and name}}
+#' \if{latex}{\figure{linetype_table.pdf}}
+#'
+#'
 #' @seealso
 #' The documentation for [differentiation related aesthetics][aes_linetype_size_shape].
 #'
@@ -35,22 +42,20 @@
 #'   scale_linetype_identity() +
 #'   facet_grid(linetype ~ .) +
 #'   theme_void(20)
-scale_linetype <- function(name = waiver(), ..., na.value = NA, aesthetics = "linetype") {
+scale_linetype <- function(name = waiver(), ..., aesthetics = "linetype") {
   discrete_scale(
     aesthetics, name = name,
     palette = NULL,
-    na.value = na.value,
     ...
   )
 }
 
 #' @rdname scale_linetype
 #' @export
-scale_linetype_binned <- function(name = waiver(), ..., na.value = NA, aesthetics = "linetype") {
+scale_linetype_binned <- function(name = waiver(), ..., aesthetics = "linetype") {
   binned_scale(
     aesthetics, name = name,
     palette = NULL,
-    na.value = na.value,
     ...
   )
 }

R/utilities-grid.R

@@ -41,6 +41,9 @@
     stroke[is.na(stroke)] <- 0
     args$fontsize <- pointsize * .pt + stroke * .stroke / 2
   }
+  if (!is.null(args$lty) && anyNA(args$lty)) {
+    args$lty[is.na(args$lty)] <- if (is.character(args$lty)) "blank" else 0
+  }
 
   inject(gpar(!!!args))
 }