FEATURE: support custom icons in themes (#7155)

* First take

* Add support for sprites in themes

Automatically register any custom icons added via themes or plugins

* Fix theme sprite caching

* Simplify test

* Update lib/svg_sprite/svg_sprite.rb

Co-Authored-By: pmusaraj <pmusaraj@gmail.com>

* Fix /svg-sprite/search request

lib/svg_sprite/svg_sprite.rb

@@ -189,8 +189,28 @@ module SvgSprite
 
   FA_ICON_MAP = { 'far fa-' => 'far-', 'fab fa-' => 'fab-', 'fas fa-' => '', 'fa-' => '' }
 
-  SVG_SPRITE_PATHS = Dir.glob(["#{Rails.root}/vendor/assets/svg-icons/**/*.svg",
-                               "#{Rails.root}/plugins/*/svg-icons/*.svg"])
+  CORE_SVG_SPRITES = Dir.glob("#{Rails.root}/vendor/assets/svg-icons/**/*.svg")
+
+  THEME_SPRITE_VAR_NAME = "icons-sprite"
+
+  def self.custom_svg_sprites(theme_ids = [])
+    custom_sprite_paths = Dir.glob("#{Rails.root}/plugins/*/svg-icons/*.svg")
+
+    ThemeField.where(type_id: ThemeField.types[:theme_upload_var], name: THEME_SPRITE_VAR_NAME, theme_id: Theme.transform_ids(theme_ids))
+      .pluck(:upload_id).each do |upload_id|
+
+      upload = Upload.find(upload_id)
+      original_path = Discourse.store.path_for(upload)
+      if original_path.blank?
+        external_copy = Discourse.store.download(upload) rescue nil
+        original_path = external_copy.try(:path)
+      end
+
+      custom_sprite_paths << Discourse.store.path_for(upload) if original_path.present?
+    end
+
+    custom_sprite_paths
+  end
 
   def self.all_icons(theme_ids = [])
     get_set_cache("icons_#{Theme.transform_ids(theme_ids).join(',')}") do
@@ -200,6 +220,7 @@ module SvgSprite
         .merge(badge_icons)
         .merge(group_icons)
         .merge(theme_icons(theme_ids))
+        .merge(custom_icons(theme_ids))
         .delete_if { |i| i.blank? || i.include?("/") }
         .map! { |i| process(i.dup) }
         .merge(SVG_ICONS)
@@ -221,11 +242,13 @@ module SvgSprite
     cache&.clear
   end
 
+  def self.sprite_sources(theme_ids)
+    CORE_SVG_SPRITES | custom_svg_sprites(theme_ids)
+  end
+
   def self.bundle(theme_ids = [])
     icons = all_icons(theme_ids)
 
-    doc = File.open("#{Rails.root}/vendor/assets/svg-icons/fontawesome/solid.svg") { |f| Nokogiri::XML(f) }
-
     svg_subset = """<!--
 Discourse SVG subset of Font Awesome Free by @fontawesome - https://fontawesome.com
 License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License)
@@ -233,7 +256,7 @@ License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL
 <svg xmlns='http://www.w3.org/2000/svg' style='display: none;'>
 """.dup
 
-    SVG_SPRITE_PATHS.each do |fname|
+    sprite_sources(theme_ids).each do |fname|
       svg_file = Nokogiri::XML(File.open(fname)) do |config|
         config.options = Nokogiri::XML::ParseOptions::NOBLANKS
       end
@@ -256,7 +279,7 @@ License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL
   def self.search(searched_icon)
     searched_icon = process(searched_icon.dup)
 
-    SVG_SPRITE_PATHS.each do |fname|
+    sprite_sources([SiteSetting.default_theme_id]).each do |fname|
       svg_file = Nokogiri::XML(File.open(fname))
       svg_filename = "#{File.basename(fname, ".svg")}"
 
@@ -274,6 +297,10 @@ License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL
     false
   end
 
+  def self.theme_sprite_variable_name
+    THEME_SPRITE_VAR_NAME
+  end
+
   def self.prepare_symbol(symbol, svg_filename)
     icon_id = symbol.attr('id')
 
@@ -331,6 +358,19 @@ License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL
     theme_icon_settings
   end
 
+  def self.custom_icons(theme_ids)
+    # Automatically register icons in sprites added via themes or plugins
+    icons = []
+    custom_svg_sprites(theme_ids).each do |fname|
+      svg_file = Nokogiri::XML(File.open(fname))
+
+      svg_file.css('symbol').each do |sym|
+        icons << sym.attributes['id'].value
+      end
+    end
+    icons
+  end
+
   def self.fa4_shim_file
     "#{Rails.root}/lib/svg_sprite/fa4-renames.json"
   end