chore: Enable return of dependency CSS as Sass files (#4044)

* chore: Enable return of dependency CSS as Sass files

Makes it possible to extract the Sass files prior to compilation for the following CSS:

* shiny
* selectize
* ionrangeslider
* daterange picker

* refactor: Take a more functional approach

* fix: missing selectizeDir

* rename: __SassLayer --> __Sass

R/input-date.R

@@ -153,6 +153,12 @@ datePickerDependency <- function(theme) {
   )
 }
 
+datePickerSass <- function() {
+  sass::sass_file(
+    system_file(package = "shiny", "www/shared/datepicker/scss/build3.scss")
+  )
+}
+
 datePickerCSS <- function(theme) {
   if (!is_bs_theme(theme)) {
     return(htmlDependency(
@@ -164,10 +170,8 @@ datePickerCSS <- function(theme) {
     ))
   }
 
-  scss_file <- system_file(package = "shiny", "www/shared/datepicker/scss/build3.scss")
-
   bslib::bs_dependency(
-    input = sass::sass_file(scss_file),
+    input = datePickerSass(),
     theme = theme,
     name = "bootstrap-datepicker",
     version = version_bs_date_picker,

R/input-select.R

@@ -241,22 +241,20 @@ selectizeDependencyFunc <- function(theme) {
     return(selectizeStaticDependency(version_selectize))
   }
 
-  selectizeDir <- system_file(package = "shiny", "www/shared/selectize/")
   bs_version <- bslib::theme_version(theme)
-  stylesheet <- file.path(
-    selectizeDir, "scss", paste0("selectize.bootstrap", bs_version, ".scss")
-  )
+
   # It'd be cleaner to ship the JS in a separate, href-based,
   # HTML dependency (which we currently do for other themable widgets),
   # but DT, crosstalk, and maybe other pkgs include selectize JS/CSS
   # in HTML dependency named selectize, so if we were to change that
   # name, the JS/CSS would be loaded/included twice, which leads to
   # strange issues, especially since we now include a 3rd party
   # accessibility plugin https://github.com/rstudio/shiny/pull/3153
+  selectizeDir <- system_file(package = "shiny", "www/shared/selectize/")
   script <- file.path(selectizeDir, selectizeScripts())
 
   bslib::bs_dependency(
-    input = sass::sass_file(stylesheet),
+    input = selectizeSass(bs_version),
     theme = theme,
     name = "selectize",
     version = version_selectize,
@@ -265,6 +263,14 @@ selectizeDependencyFunc <- function(theme) {
   )
 }
 
+selectizeSass <- function(bs_version) {
+  selectizeDir <- system_file(package = "shiny", "www/shared/selectize/")
+  stylesheet <- file.path(
+    selectizeDir, "scss", paste0("selectize.bootstrap", bs_version, ".scss")
+  )
+  sass::sass_file(stylesheet)
+}
+
 selectizeStaticDependency <- function(version) {
   htmlDependency(
     "selectize",

R/input-slider.R

@@ -222,6 +222,15 @@ ionRangeSliderDependency <- function() {
   )
 }
 
+ionRangeSliderDependencySass <- function() {
+  list(
+    list(accent = "$component-active-bg"),
+    sass::sass_file(
+      system_file(package = "shiny", "www/shared/ionrangeslider/scss/shiny.scss")
+    )
+  )
+}
+
 ionRangeSliderDependencyCSS <- function(theme) {
   if (!is_bs_theme(theme)) {
     return(htmlDependency(
@@ -234,12 +243,7 @@ ionRangeSliderDependencyCSS <- function(theme) {
   }
 
   bslib::bs_dependency(
-    input = list(
-      list(accent = "$component-active-bg"),
-      sass::sass_file(
-        system_file(package = "shiny", "www/shared/ionrangeslider/scss/shiny.scss")
-      )
-    ),
+    input = ionRangeSliderDependencySass(),
     theme = theme,
     name = "ionRangeSlider",
     version = version_ion_range_slider,

R/shinyui.R

@@ -135,6 +135,14 @@ shinyDependencies <- function() {
   )
 }
 
+shinyDependencySass <- function(bs_version) {
+  bootstrap_scss <- paste0("shiny.bootstrap", bs_version, ".scss")
+
+  scss_home <- system_file("www/shared/shiny_scss", package = "shiny")
+  scss_files <- file.path(scss_home, c(bootstrap_scss, "shiny.scss"))
+  lapply(scss_files, sass::sass_file)
+}
+
 shinyDependencyCSS <- function(theme) {
   version <- get_package_version("shiny")
 
@@ -150,14 +158,9 @@ shinyDependencyCSS <- function(theme) {
   }
 
   bs_version <- bslib::theme_version(theme)
-  bootstrap_scss <- paste0("shiny.bootstrap", bs_version, ".scss")
-
-  scss_home <- system_file("www/shared/shiny_scss", package = "shiny")
-  scss_files <- file.path(scss_home, c(bootstrap_scss, "shiny.scss"))
-  scss_files <- lapply(scss_files, sass::sass_file)
 
   bslib::bs_dependency(
-    input = scss_files,
+    input = shinyDependencySass(bs_version),
     theme = theme,
     name = "shiny-sass",
     version = version,