FEATURE: Enable auto dark mode on new instances (discourse#14208)

db/fixtures/600_themes.rb

@@ -18,4 +18,12 @@
   name = I18n.t('color_schemes.default_theme_name')
   default_theme = Theme.create!(name: name, user_id: -1)
   default_theme.set_default!
+
+  if SiteSetting.default_dark_mode_color_scheme_id == SiteSetting.defaults[:default_dark_mode_color_scheme_id]
+    dark_scheme_id = ColorScheme.where(base_scheme_id: "Dark").pluck_first(:id)
+
+    if dark_scheme_id.present?
+      SiteSetting.default_dark_mode_color_scheme_id = dark_scheme_id
+    end
+  end
 end

lib/wizard/builder.rb

@@ -203,6 +203,14 @@ def build
           updater.update_setting(:base_font, updater.fields[:body_font])
           updater.update_setting(:heading_font, updater.fields[:heading_font])
 
+          if updater.fields[:homepage_style] == 'latest'
+            top_menu = "latest|new|unread|top|categories"
+          else
+            top_menu = "categories|latest|new|unread|top"
+            updater.update_setting(:desktop_category_page_style, updater.fields[:homepage_style])
+          end
+          updater.update_setting(:top_menu, top_menu)
+
           scheme_name = (
             (updater.fields[:color_scheme] || "") ||
             ColorScheme::LIGHT_THEME_ID
@@ -228,13 +236,9 @@ def build
             theme.set_default!
           end
 
-          if updater.fields[:homepage_style] == 'latest'
-            top_menu = "latest|new|unread|top|categories"
-          else
-            top_menu = "categories|latest|new|unread|top"
-            updater.update_setting(:desktop_category_page_style, updater.fields[:homepage_style])
+          if scheme.is_dark?
+            updater.update_setting(:default_dark_mode_color_scheme_id, -1)
           end
-          updater.update_setting(:top_menu, top_menu)
         end
       end
 

spec/components/wizard/step_updater_spec.rb

@@ -169,7 +169,11 @@
 
   context "styling step" do
     it "updates fonts" do
-      updater = wizard.create_updater('styling', body_font: 'open_sans', heading_font: 'oswald')
+      updater = wizard.create_updater('styling',
+        body_font: 'open_sans',
+        heading_font: 'oswald',
+        homepage_style: 'latest'
+      )
       updater.update
       expect(updater.success?).to eq(true)
       expect(wizard.completed_steps?('styling')).to eq(true)
@@ -182,7 +186,12 @@
         fab!(:color_scheme) { Fabricate(:color_scheme, name: 'existing', via_wizard: true) }
 
         it "updates the scheme" do
-          updater = wizard.create_updater('styling', color_scheme: 'Dark', body_font: 'arial', heading_font: 'arial', homepage_style: 'latest')
+          updater = wizard.create_updater('styling',
+            color_scheme: 'Dark',
+            body_font: 'arial',
+            heading_font: 'arial',
+            homepage_style: 'latest'
+          )
           updater.update
           expect(updater.success?).to eq(true)
           expect(wizard.completed_steps?('styling')).to eq(true)
@@ -277,12 +286,41 @@
           expect(theme.color_scheme_id).to eq(color_scheme.id)
         end
       end
+
+      context "auto dark mode" do
+        before do
+          dark_scheme = ColorScheme.where(name: "Dark").first
+          SiteSetting.default_dark_mode_color_scheme_id = dark_scheme.id
+        end
+
+        it "does nothing when selected scheme is light" do
+          updater = wizard.create_updater('styling',
+            color_scheme: 'Neutral',
+            body_font: 'arial',
+            heading_font: 'arial',
+            homepage_style: 'latest'
+          )
+
+          expect { updater.update }.not_to change { SiteSetting.default_dark_mode_color_scheme_id }
+        end
+
+        it "unsets auto dark mode site setting when default selected scheme is also dark" do
+          updater = wizard.create_updater('styling',
+            color_scheme: 'Latte',
+            body_font: 'arial',
+            heading_font: 'arial',
+            homepage_style: 'latest'
+          )
+
+          expect { updater.update }.to change { SiteSetting.default_dark_mode_color_scheme_id }.to(-1)
+        end
+      end
+
     end
 
     context "homepage style" do
       it "updates the fields correctly" do
         updater = wizard.create_updater('styling',
-          color_scheme: 'Dark',
           body_font: 'arial',
           heading_font: 'arial',
           homepage_style: "categories_and_top_topics"
@@ -295,7 +333,6 @@
         expect(SiteSetting.desktop_category_page_style).to eq('categories_and_top_topics')
 
         updater = wizard.create_updater('styling',
-          color_scheme: 'Dark',
           body_font: 'arial',
           heading_font: 'arial',
           homepage_style: "latest"