allow guide_axis_nested(key) to be a sep argument

R/guide_axis_nested.R

@@ -5,9 +5,12 @@
 #' This axis guide gives extra range annotations to position scales. It can
 #' be used to infer nesting structure from labels or annotate ranges.
 #'
-#' @param key A [range key][key_range] specification. If not
-#'   `key = "range_auto"`, additional labels will be inserted to represent
-#'   point values.
+#' @param key One of the following:
+#'   * A [range key][key_range] specification. If not `key = "range_auto"`,
+#'     additional labels will be inserted to represent point values.
+#'   * A `<character[1]>` passed to the [`key_range_auto(sep)`][key_range_auto]
+#'     argument. An exception is made when the string is a valid key
+#'     specification.
 #' @param regular_key A [standard key][key_standard] specification for the
 #'   appearance of regular tick marks.
 #' @param type Appearance of ranges, either `"box"` to put text in boxes or
@@ -106,6 +109,9 @@ guide_axis_nested <- function(
   )
   pad_discrete <- pad_discrete %||% switch(type, fence = 0.5, 0.4)
 
+  if (is_string(key) && !is_key_string(key)) {
+    key <- key_range_auto(sep = key)
+  }
   if (identical(key, "range_auto") ||
       inherits(key, "key_range_auto_function")) {
     labels <- guide_none()

R/key-.R

@@ -219,6 +219,14 @@ resolve_key <- function(x, allow_null = FALSE) {
   cli::cli_abort("Unknown key specification: {x}.")
 }
 
+is_key_string <- function(x) {
+  if (!is_bare_string(x)) {
+    return(FALSE)
+  }
+  fun <- find_global(paste0("key_", x), env = global_env(), mode = "function")
+  is.function(fun)
+}
+
 log10_keys <- function(scale, aesthetic,
                        prescale_base = NULL,
                        negative_small = 0.1,