change regex pattern to match valid css class names (#69)

* The style functions are now more permissive about color names in the `color` argument. Color names should be valid CSS classes that can also be used as CSS variable names, but the `style_` function only stops with an error if the color name contains spaces. (@jdlom #69)

R/color.R

@@ -121,8 +121,13 @@ prepare_colors <- function(colors = NULL) {
       call. = FALSE)
   }
 
-  if (any(grepl("[^[:alpha:]_-]", names(colors)))) {
-    stop("Color names in `colors` must be valid CSS classes", call. = FALSE)
+  maybe_bad_css <- unique(grep("^[_-]|[ .>~*:|+}/]", names(colors), value = TRUE))
+  if (length(maybe_bad_css) > 0) {
+    warning(
+      "Color names in `colors` should be valid CSS classes: ",
+      paste0("'", maybe_bad_css, "'", collapse = ", "),
+      call. = FALSE
+    )
   }
 
   whisker::iteratelist(colors, "color_name")

tests/testthat/test-color.R

@@ -13,9 +13,23 @@ describe("prepare_colors()", {
 
   it("requires valid CSS names", {
     expect_error(prepare_colors(c("light blue" = "#88f")))
-    expect_error(prepare_colors(c("light/blue" = "#88f")))
+    expect_warning(prepare_colors(c("light/blue" = "#88f")), "light/blue")
+    expect_warning(prepare_colors(c("-lightblue" = "#88f")), "-lightblue")
+    expect_warning(prepare_colors(c("_lightblue" = "#88f")), "_lightblue")
+    
+    colors <- c("light_blue" = "#88f", "light-blue" = "#88f")
+    expect_silent(
+      expect_equal(
+        prepare_colors(colors),
+        list(
+          list(color_name = "light_blue", value = "#88f"),
+          list(color_name = "light-blue", value = "#88f")
+        )
+      )
+    )
   })
 
+
   it("returns list with color_name and value for each color", {
     colors <- c('test' = "#4ed4ed")
     prepared <- prepare_colors(colors)