UX: Conditionally refresh page on wizard styling step (#31193)

Previously, were always forcing the page to reload
for the wizard after pressing Next for the styling step,
with the logic that if style changes are being made,
the admin needs to see them straight away.

However this doesn't make sense if nothing changes on
that step. This commit makes the change to only refresh
the page if any of the settings on the step changed,
bringing it in line with other steps.

lib/wizard/builder.rb

@@ -265,6 +265,10 @@ class Wizard
 
           scheme_name = ((updater.fields[:color_scheme] || "") || ColorScheme::LIGHT_THEME_ID)
 
+          if updater.setting_changed?(:base_font) || updater.setting_changed?(:heading_font)
+            updater.refresh_required = true
+          end
+
           next unless scheme_name.present? && ColorScheme.is_base?(scheme_name)
 
           name = I18n.t("color_schemes.#{scheme_name.downcase.gsub(" ", "_")}_theme_name")
@@ -273,9 +277,13 @@ class Wizard
           scheme ||=
             ColorScheme.create_from_base(name: name, via_wizard: true, base_scheme_id: scheme_name)
 
+          theme_changed = false
           if default_theme
-            default_theme.color_scheme_id = scheme.id
-            default_theme.save!
+            if default_theme.color_scheme_id != scheme.id
+              default_theme.color_scheme_id = scheme.id
+              default_theme.save!
+              theme_changed = true
+            end
           else
             theme =
               Theme.create!(
@@ -285,10 +293,14 @@ class Wizard
               )
 
             theme.set_default!
+            theme_changed = true
           end
 
           updater.update_setting(:default_dark_mode_color_scheme_id, -1) if scheme.is_dark?
-          updater.refresh_required = true
+
+          if updater.setting_changed?(:default_dark_mode_color_scheme_id) || theme_changed
+            updater.refresh_required = true
+          end
         end
       end
     end

lib/wizard/step_updater.rb

@@ -11,6 +11,7 @@ class Wizard
       @step = step
       @refresh_required = false
       @fields = fields
+      @settings_changed = Set.new
     end
 
     def update
@@ -30,6 +31,10 @@ class Wizard
       @refresh_required
     end
 
+    def setting_changed?(id)
+      @settings_changed.include?(id)
+    end
+
     def update_setting(id, value)
       value = value.strip if value.is_a?(String)
 
@@ -37,7 +42,10 @@ class Wizard
         value = Upload.get_from_url(value) || ""
       end
 
-      SiteSetting.set_and_log(id, value, @current_user) if SiteSetting.get(id) != value
+      if SiteSetting.get(id) != value
+        SiteSetting.set_and_log(id, value, @current_user)
+        @settings_changed << id
+      end
     end
 
     def apply_setting(id)

spec/lib/wizard/step_updater_spec.rb

@@ -91,6 +91,7 @@ RSpec.describe Wizard::StepUpdater do
         )
       updater.update
       expect(updater.success?).to eq(true)
+      expect(updater.refresh_required?).to eq(true)
       expect(wizard.completed_steps?("styling")).to eq(true)
       expect(SiteSetting.base_font).to eq("open_sans")
       expect(SiteSetting.heading_font).to eq("oswald")
@@ -100,11 +101,32 @@ RSpec.describe Wizard::StepUpdater do
       updater = wizard.create_updater("styling", site_font: "open_sans", homepage_style: "latest")
       updater.update
       expect(updater.success?).to eq(true)
+      expect(updater.refresh_required?).to eq(true)
       expect(wizard.completed_steps?("styling")).to eq(true)
       expect(SiteSetting.base_font).to eq("open_sans")
       expect(SiteSetting.heading_font).to eq("open_sans")
     end
 
+    it "does not require refresh if the font, color scheme, or theme are unchanged" do
+      SiteSetting.base_font = "open_sans"
+      SiteSetting.heading_font = "open_sans"
+      SiteSetting.top_menu = "latest|categories|unread|top"
+      dark_scheme = ColorScheme.find_by(name: "Dark")
+      Theme.find_default.update!(color_scheme: dark_scheme)
+      SiteSetting.default_dark_mode_color_scheme_id = -1
+      updater =
+        wizard.create_updater(
+          "styling",
+          color_scheme: "Dark",
+          site_font: "open_sans",
+          heading_font: "open_sans",
+          homepage_style: "latest",
+        )
+      updater.update
+      expect(updater.success?).to eq(true)
+      expect(updater.refresh_required?).to eq(false)
+    end
+
     context "with colors" do
       context "with an existing color scheme" do
         fab!(:color_scheme) { Fabricate(:color_scheme, name: "existing", via_wizard: true) }