Improve the mountby selector

Using symbols instead of strings for its items key.

src/lib/autoinstall/widgets/storage/filesystem_attrs.rb

@@ -89,7 +89,7 @@ def values
             "filesystem"    => filesystem_widget.value,
             "label"         => label_widget.value,
             "mount"         => mount_point_widget.value,
-            "mountby"       => mountby_widget.value&.to_sym,
+            "mountby"       => mountby_widget.value,
             "fstab_options" => fstab_options_widget.value,
             "mkfs_options"  => mkfs_options_widget.value
           }

src/lib/autoinstall/widgets/storage/mountby.rb

@@ -40,19 +40,10 @@ def label
         # @macro seeComboBox
         def items
           @items ||= [
-            ["", ""],
-            *Y2Storage::Filesystems::MountByType.all.map { |i| [i.to_s, i.to_human_string] }
+            [nil, ""],
+            *Y2Storage::Filesystems::MountByType.all.map { |i| [i.to_sym, i.to_human_string] }
           ]
         end
-
-        # Returns selected type
-        #
-        # @return [String, nil] selected type; nil if none
-        def value
-          result = super
-
-          result.to_s.empty? ? nil : result
-        end
       end
     end
   end

test/lib/widgets/storage/mountby_test.rb

@@ -24,33 +24,33 @@
 describe Y2Autoinstallation::Widgets::Storage::Mountby do
   subject(:widget) { described_class.new }
 
-  include_examples "CWM::ComboBox"
-
-  let(:items) { widget.items.map { |i| i[0] } }
+  include_examples "CWM::AbstractWidget"
 
   describe "#items" do
+    let(:items) { widget.items.map { |i| i[0] } }
+
     it "includes an empty option" do
-      expect(items).to include("")
+      expect(items).to include(nil)
     end
 
-    it "includes 'device'" do
-      expect(items).to include("device")
+    it "includes :device" do
+      expect(items).to include(:device)
     end
 
-    it "includes 'label'" do
-      expect(items).to include("label")
+    it "includes :label" do
+      expect(items).to include(:label)
     end
 
-    it "includes 'uuid'" do
-      expect(items).to include("uuid")
+    it "includes :uuid" do
+      expect(items).to include(:uuid)
     end
 
-    it "includes 'path'" do
-      expect(items).to include("path")
+    it "includes :path" do
+      expect(items).to include(:path)
     end
 
-    it "includes 'id'" do
-      expect(items).to include("id")
+    it "includes :id" do
+      expect(items).to include(:id)
     end
   end
 
@@ -61,15 +61,15 @@
     end
 
     describe "when none is selected" do
-      let(:selected_value) { "" }
+      let(:selected_value) { nil }
 
       it "returns nil" do
         expect(widget.value).to be_nil
       end
     end
 
     describe "when any is selected" do
-      let(:selected_value) { "path" }
+      let(:selected_value) { :path }
 
       it "returns selected value" do
         expect(widget.value).to eq(selected_value)