Fix expression labels in guide_coloursteps() and guide_bins() (#6007)

* cast expressions to lists

* additional workaround for expressions

* linearise discrete `get_labels()` logic

* scales cast expressions as lists

* alleviate wrangling label expressions

* fix deprecated argument name

* add news bullets

* revert even.steps logic

Author: teunbrand

NEWS.md

@@ -1,5 +1,7 @@
 # ggplot2 (development version)
 
+* Binned guides now accept expressions as labels (@teunbrand, #6005)
+* (internal) `Scale$get_labels()` format expressions as lists.
 * In non-orthogonal coordinate systems (`coord_sf()`, `coord_polar()` and 
   `coord_radial()`), using 'AsIs' variables escape transformation when
   both `x` and `y` is an 'AsIs' variable (@teunbrand, #6205).

R/guide-.R

@@ -225,13 +225,8 @@ Guide <- ggproto(
 
     mapped <- scale$map(breaks)
     labels <- scale$get_labels(breaks)
-    # {vctrs} doesn't play nice with expressions, convert to list.
-    # see also https://github.com/r-lib/vctrs/issues/559
-    if (is.expression(labels)) {
-      labels <- as.list(labels)
-    }
 
-    key <- data_frame(mapped, .name_repair = ~ aesthetic)
+    key <- data_frame(!!aesthetic := mapped)
     key$.value <- breaks
     key$.label <- labels
 

R/guide-axis-theta.R

@@ -110,7 +110,7 @@ GuideAxisTheta <- ggproto(
       # labels of these positions
       ends_apart <- (key$theta[n] - key$theta[1]) %% (2 * pi)
       if (n > 0 && ends_apart < 0.05 && !is.null(key$.label)) {
-        if (is.expression(key$.label)) {
+        if (is.expression(key$.label[[1]])) {
           combined <- substitute(
             paste(a, "/", b),
             list(a = key$.label[[1]], b = key$.label[[n]])

R/guide-bins.R

@@ -161,7 +161,7 @@ GuideBins <- ggproto(
     key$.show  <- NA
 
     labels <- scale$get_labels(breaks)
-    if (is.character(scale$labels) || is.numeric(scale$labels)) {
+    if (is.character(scale$labels) || is.numeric(scale$labels) || is.expression(scale$labels)) {
       limit_lab <- c(NA, NA)
     } else {
       limit_lab <- scale$get_labels(limits)
@@ -265,7 +265,7 @@ GuideBins <- ggproto(
 
     list(labels = flip_element_grob(
       elements$text,
-      label = key$.label,
+      label = validate_labels(key$.label),
       x = unit(key$.value, "npc"),
       margin_x = FALSE,
       margin_y = TRUE,

R/scale-.R

@@ -861,12 +861,9 @@ ScaleContinuous <- ggproto("ScaleContinuous", Scale,
       labels[lengths(labels) == 0] <- ""
       # Make sure each element is scalar
       labels <- lapply(labels, `[`, 1)
-
-      if (any(vapply(labels, is.language, logical(1)))) {
-        labels <- inject(expression(!!!labels))
-      } else {
-        labels <- unlist(labels)
-      }
+    }
+    if (is.expression(labels)) {
+      labels <- as.list(labels)
     }
 
     labels
@@ -1074,48 +1071,42 @@ ScaleDiscrete <- ggproto("ScaleDiscrete", Scale,
       return(NULL)
     }
 
-    if (is.null(self$labels)) {
+    labels <- self$labels
+    if (is.null(labels)) {
       return(NULL)
     }
 
-    if (identical(self$labels, NA)) {
+    if (identical(labels, NA)) {
       cli::cli_abort(
         "Invalid {.arg labels} specification. Use {.code NULL}, not {.code NA}.",
         call = self$call
       )
     }
 
-    if (is.waiver(self$labels)) {
+    if (is.waiver(labels)) {
       if (!is.null(names(breaks))) {
-        return(names(breaks))
-      }
-      if (is.numeric(breaks)) {
+        labels <- names(breaks)
+      } else if (is.numeric(breaks)) {
         # Only format numbers, because on Windows, format messes up encoding
-        format(breaks, justify = "none")
+        labels <- format(breaks, justify = "none")
       } else {
-        as.character(breaks)
+        labels <- as.character(breaks)
       }
-    } else if (is.function(self$labels)) {
-      self$labels(breaks)
-    } else {
-      if (!is.null(names(self$labels))) {
-        # If labels have names, use them to match with breaks
-        labels <- breaks
-
-        map <- match(names(self$labels), labels, nomatch = 0)
-        labels[map] <- self$labels[map != 0]
-        labels
-      } else {
-        labels <- self$labels
+    } else if (is.function(labels)) {
+      labels <- labels(breaks)
+    } else if (!is.null(names(labels))) {
+      # If labels have names, use them to match with breaks
+      map <- match(names(self$labels), breaks, nomatch = 0)
+      labels <- replace(breaks, map, labels[map != 0])
+    } else if (!is.null(attr(breaks, "pos"))) {
+      # Need to ensure that if breaks were dropped, corresponding labels are too
+      labels <- labels[attr(breaks, "pos")]
+    }
 
-        # Need to ensure that if breaks were dropped, corresponding labels are too
-        pos <- attr(breaks, "pos")
-        if (!is.null(pos)) {
-          labels <- labels[pos]
-        }
-        labels
-      }
+    if (is.expression(labels)) {
+      labels <- as.list(labels)
     }
+    labels
   },
 
   clone = function(self) {
@@ -1351,6 +1342,9 @@ ScaleBinned <- ggproto("ScaleBinned", Scale,
         call = self$call
       )
     }
+    if (is.expression(labels)) {
+      labels <- as.list(labels)
+    }
     labels
   },