FIX: Regression in custom homepage modifier used in theme components (#27569)

app/controllers/application_controller.rb

@@ -492,7 +492,7 @@ class ApplicationController < ActionController::Base
   end
 
   def current_homepage
-    current_user&.user_option&.homepage || HomepageHelper.resolve(@theme_id, current_user)
+    current_user&.user_option&.homepage || HomepageHelper.resolve(request, current_user)
   end
 
   def serialize_data(obj, serializer, opts = nil)

app/helpers/application_helper.rb

@@ -560,7 +560,7 @@ module ApplicationHelper
   end
 
   def current_homepage
-    current_user&.user_option&.homepage || HomepageHelper.resolve(theme_id, current_user)
+    current_user&.user_option&.homepage || HomepageHelper.resolve(request, current_user)
   end
 
   def build_plugin_html(name)

lib/homepage_constraint.rb

@@ -9,11 +9,10 @@ class HomePageConstraint
     return @filter == "finish_installation" if SiteSetting.has_login_hint?
 
     current_user = CurrentUser.lookup_from_env(request.env)
-
     # ensures we resolve the theme id as early as possible
-    theme_id = ThemeResolver.resolve_theme_id(request, Guardian.new(current_user), current_user)
+    ThemeResolver.resolve_theme_id(request, Guardian.new(current_user), current_user)
 
-    homepage = current_user&.user_option&.homepage || HomepageHelper.resolve(theme_id, current_user)
+    homepage = current_user&.user_option&.homepage || HomepageHelper.resolve(request, current_user)
     homepage == @filter
   rescue Discourse::InvalidAccess, Discourse::ReadOnly
     false

lib/homepage_helper.rb

@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
 class HomepageHelper
-  def self.resolve(theme_id = nil, current_user = nil)
-    return "custom" if ThemeModifierHelper.new(theme_ids: theme_id).custom_homepage
+  def self.resolve(request = nil, current_user = nil)
+    return "custom" if ThemeModifierHelper.new(request: request).custom_homepage
 
     current_user ? SiteSetting.homepage : SiteSetting.anonymous_homepage
   end

spec/system/homepage_spec.rb

@@ -53,29 +53,6 @@ describe "Homepage", type: :system do
     expect(page).to have_css(".navigation-container .categories.active", text: "Categories")
   end
 
-  context "when default theme uses a custom_homepage modifier" do
-    before do
-      theme.theme_modifier_set.custom_homepage = true
-      theme.theme_modifier_set.save!
-      theme.set_default!
-    end
-
-    it "shows empty state to regular users" do
-      sign_in user
-      visit "/"
-
-      expect(page).to have_no_css(".list-container")
-      expect(page).to have_no_css(".alert-info")
-    end
-
-    it "shows empty state and notice to admins" do
-      sign_in admin
-      visit "/"
-
-      expect(page).to have_no_css(".list-container")
-      expect(page).to have_css(".alert-info")
-    end
-
   shared_examples "a custom homepage" do
     it "shows the custom homepage component" do
       visit "/"
@@ -134,6 +111,29 @@ describe "Homepage", type: :system do
     end
   end
 
+  context "when default theme uses a custom_homepage modifier" do
+    before do
+      theme.theme_modifier_set.custom_homepage = true
+      theme.theme_modifier_set.save!
+      theme.set_default!
+    end
+
+    it "shows empty state to regular users" do
+      sign_in user
+      visit "/"
+
+      expect(page).to have_no_css(".list-container")
+      expect(page).to have_no_css(".alert-info")
+    end
+
+    it "shows empty state and notice to admins" do
+      sign_in admin
+      visit "/"
+
+      expect(page).to have_no_css(".list-container")
+      expect(page).to have_css(".alert-info")
+    end
+
     context "when the theme adds content to the [custom-homepage] connector" do
       let!(:basic_html_field) do
         Fabricate(
@@ -175,4 +175,31 @@ describe "Homepage", type: :system do
       include_examples "a custom homepage"
     end
   end
+
+  context "when a theme component uses the custom_homepage modifier" do
+    let!(:component) { Fabricate(:theme, component: true) }
+    let!(:component_html_field) do
+      Fabricate(
+        :theme_field,
+        theme: component,
+        type_id: ThemeField.types[:html],
+        target_id: Theme.targets[:common],
+        name: "head_tag",
+        value: <<~HTML,
+            <script type="text/x-handlebars" data-template-name="/connectors/custom-homepage/new-home">
+              <div class="new-home">Hi friends!</div>
+            </script>
+          HTML
+      )
+    end
+
+    before do
+      component.theme_modifier_set.custom_homepage = true
+      component.theme_modifier_set.save!
+      theme.add_relative_theme!(:child, component)
+      theme.set_default!
+    end
+
+    include_examples "a custom homepage"
+  end
 end