FEATURE: backend support for user-selectable components

* FEATURE: backend support for user-selectable components

* fix problems with previewing default theme

* rename preview_key => preview_theme_id

* omit default theme from child themes dropdown and try a different fix

* cache & freeze stylesheets arrays

app/assets/javascripts/admin/controllers/admin-customize-themes-show.js.es6

@@ -1,4 +1,7 @@
-import { default as computed } from "ember-addons/ember-computed-decorators";
+import {
+  default as computed,
+  observes
+} from "ember-addons/ember-computed-decorators";
 import { url } from "discourse/lib/computed";
 import { popupAjaxError } from "discourse/lib/ajax-error";
 import showModal from "discourse/lib/show-modal";
@@ -9,6 +12,18 @@ const THEME_UPLOAD_VAR = 2;
 export default Ember.Controller.extend({
   editRouteName: "adminCustomizeThemes.edit",
 
+  @observes("allowChildThemes")
+  setSelectedThemeId() {
+    const available = this.get("selectableChildThemes");
+    if (
+      !this.get("selectedChildThemeId") &&
+      available &&
+      available.length > 0
+    ) {
+      this.set("selectedChildThemeId", available[0].get("id"));
+    }
+  },
+
   @computed("model", "allThemes")
   parentThemes(model, allThemes) {
     let parents = allThemes.filter(theme =>
@@ -64,16 +79,21 @@ export default Ember.Controller.extend({
 
     let themes = [];
     available.forEach(t => {
-      if (!childThemes || childThemes.indexOf(t) === -1) {
+      if (
+        (!childThemes || childThemes.indexOf(t) === -1) &&
+        Em.isEmpty(t.get("childThemes")) &&
+        !t.get("user_selectable") &&
+        !t.get("default")
+      ) {
         themes.push(t);
       }
     });
     return themes.length === 0 ? null : themes;
   },
 
-  @computed("allThemes", "allThemes.length", "model")
+  @computed("allThemes", "allThemes.length", "model", "parentThemes")
   availableChildThemes(allThemes, count) {
-    if (count === 1) {
+    if (count === 1 || this.get("parentThemes")) {
       return null;
     }
 

app/assets/javascripts/admin/models/theme.js.es6

@@ -1,5 +1,6 @@
 import RestModel from "discourse/models/rest";
 import { default as computed } from "ember-addons/ember-computed-decorators";
+import { popupAjaxError } from "discourse/lib/ajax-error";
 
 const THEME_UPLOAD_VAR = 2;
 
@@ -150,7 +151,9 @@ const Theme = RestModel.extend({
 
   saveChanges() {
     const hash = this.getProperties.apply(this, arguments);
-    return this.save(hash).then(() => this.set("changed", false));
+    return this.save(hash)
+      .finally(() => this.set("changed", false))
+      .catch(popupAjaxError);
   },
 
   saveSettings(name, value) {

app/assets/javascripts/admin/templates/customize-themes-show.hbs

@@ -137,7 +137,7 @@
     {{/unless}}
     {{#if selectableChildThemes}}
       <p>
-        {{combo-box content=selectableChildThemes value=selectedChildThemeId}}
+        {{combo-box filterable=true content=selectableChildThemes value=selectedChildThemeId}}
         {{#d-button action="addChildTheme" icon="plus"}}{{i18n "admin.customize.theme.add"}}{{/d-button}}
       </p>
     {{/if}}

app/assets/javascripts/discourse/controllers/preferences/interface.js.es6

@@ -66,7 +66,7 @@ export default Ember.Controller.extend(PreferencesTabController, {
   @observes("themeId")
   themeIdChanged() {
     const id = this.get("themeId");
-    previewTheme(id);
+    previewTheme([id]);
   },
 
   homeChanged() {

app/assets/javascripts/discourse/initializers/live-development.js.es6

@@ -1,5 +1,5 @@
 import DiscourseURL from "discourse/lib/url";
-import { currentThemeId, refreshCSS } from "discourse/lib/theme-selector";
+import { currentThemeIds, refreshCSS } from "discourse/lib/theme-selector";
 
 //  Use the message bus for live reloading of components for faster development.
 export default {
@@ -58,12 +58,16 @@ export default {
           // Refresh if necessary
           document.location.reload(true);
         } else {
-          let themeId = currentThemeId();
+          const themeIds = currentThemeIds();
-
           $("link").each(function() {
             if (me.hasOwnProperty("theme_id") && me.new_href) {
-              let target = $(this).data("target");
+              const target = $(this).data("target");
-              if (me.theme_id === themeId && target === me.target) {
+              const themeId = $(this).data("theme-id");
+              if (
+                themeIds.indexOf(me.theme_id) !== -1 &&
+                target === me.target &&
+                (!themeId || themeId === me.theme_id)
+              ) {
                 refreshCSS(this, null, me.new_href);
               }
             } else if (this.href.match(me.name) && (me.hash || me.new_href)) {

app/assets/javascripts/discourse/lib/theme-selector.js.es6

@@ -1,7 +1,7 @@
 import { ajax } from "discourse/lib/ajax";
 import deprecated from "discourse-common/lib/deprecated";
 
-const keySelector = "meta[name=discourse_theme_id]";
+const keySelector = "meta[name=discourse_theme_ids]";
 
 export function currentThemeKey() {
   if (console && console.warn && console.trace) {
@@ -12,21 +12,26 @@ export function currentThemeKey() {
   }
 }
 
-export function currentThemeId() {
+export function currentThemeIds() {
-  let themeId = null;
+  const themeIds = [];
-  let elem = _.first($(keySelector));
+  const elem = _.first($(keySelector));
   if (elem) {
-    themeId = elem.content;
+    elem.content.split(",").forEach(num => {
-    if (_.isEmpty(themeId)) {
+      num = parseInt(num, 10);
-      themeId = null;
+      if (!isNaN(num)) {
-    } else {
+        themeIds.push(num);
-      themeId = parseInt(themeId);
+      }
-    }
+    });
   }
-  return themeId;
+  return themeIds;
+}
+
+export function currentThemeId() {
+  return currentThemeIds()[0];
 }
 
 export function setLocalTheme(ids, themeSeq) {
+  ids = ids.reject(id => !id);
   if (ids && ids.length > 0) {
     $.cookie("theme_ids", `${ids.join(",")}|${themeSeq}`, {
       path: "/",
@@ -76,23 +81,28 @@ export function refreshCSS(node, hash, newHref, options) {
   $orig.data("copy", reloaded);
 }
 
-export function previewTheme(id) {
+export function previewTheme(ids = []) {
-  if (currentThemeId() !== id) {
+  ids = ids.reject(id => !id);
+  if (!ids.includes(currentThemeId())) {
     Discourse.set("assetVersion", "forceRefresh");
 
-    ajax(`/themes/assets/${id ? id : "default"}`).then(results => {
+    ajax(`/themes/assets/${ids.length > 0 ? ids.join("-") : "default"}`).then(
-      let elem = _.first($(keySelector));
+      results => {
-      if (elem) {
+        const elem = _.first($(keySelector));
-        elem.content = id;
+        if (elem) {
-      }
+          elem.content = ids.join(",");
-
-      results.themes.forEach(theme => {
-        let node = $(`link[rel=stylesheet][data-target=${theme.target}]`)[0];
-        if (node) {
-          refreshCSS(node, null, theme.url, { force: true });
         }
-      });
+
-    });
+        results.themes.forEach(theme => {
+          const node = $(
+            `link[rel=stylesheet][data-target=${theme.target}]`
+          )[0];
+          if (node) {
+            refreshCSS(node, null, theme.new_href, { force: true });
+          }
+        });
+      }
+    );
   }
 }
 

app/controllers/admin/themes_controller.rb

@@ -182,11 +182,13 @@ class Admin::ThemesController < Admin::AdminController
         log_theme_change(original_json, @theme)
         format.json { render json: @theme, status: :ok }
       else
-        format.json {
+        format.json do
+          error = @theme.errors.full_messages.join(", ").presence
+          error = I18n.t("themes.bad_color_scheme") if @theme.errors[:color_scheme].present?
+          error ||= I18n.t("themes.other_error")
 
-          error = @theme.errors[:color_scheme] ? I18n.t("themes.bad_color_scheme") : I18n.t("themes.other_error")
           render json: { errors: [ error ] }, status: :unprocessable_entity
-        }
+        end
       end
     end
   end

app/controllers/application_controller.rb

@@ -22,7 +22,7 @@ class ApplicationController < ActionController::Base
   include GlobalPath
   include Hijack
 
-  attr_reader :theme_id
+  attr_reader :theme_ids
 
   serialization_scope :guardian
 
@@ -62,8 +62,8 @@ class ApplicationController < ActionController::Base
     after_action :remember_theme_id
 
     def remember_theme_id
-      if @theme_id
+      if @theme_ids.present?
-        Stylesheet::Watcher.theme_id = @theme_id if defined? Stylesheet::Watcher
+        Stylesheet::Watcher.theme_id = @theme_ids.first if defined? Stylesheet::Watcher
       end
     end
   end
@@ -331,28 +331,33 @@ class ApplicationController < ActionController::Base
     resolve_safe_mode
     return if request.env[NO_CUSTOM]
 
-    theme_id = request[:preview_theme_id]&.to_i
+    theme_ids = []
+
+    if preview_theme_id = request[:preview_theme_id]&.to_i
+      theme_ids << preview_theme_id
+    end
 
     user_option = current_user&.user_option
 
-    unless theme_id
+    if theme_ids.blank?
       ids, seq = cookies[:theme_ids]&.split("|")
       ids = ids&.split(",")&.map(&:to_i)
-      if ids && ids.size > 0 && seq && seq.to_i == user_option&.theme_key_seq.to_i
+      if ids.present? && seq && seq.to_i == user_option&.theme_key_seq.to_i
-        theme_id = ids.first
+        theme_ids = ids if guardian.allow_themes?(ids)
       end
     end
 
-    theme_id ||= user_option&.theme_ids&.first
+    theme_ids = user_option&.theme_ids || [] if theme_ids.blank?
 
-    if theme_id && !guardian.allow_themes?(theme_id)
+    unless guardian.allow_themes?(theme_ids)
-      theme_id = nil
+      theme_ids = []
     end
 
-    theme_id ||= SiteSetting.default_theme_id
+    if theme_ids.blank? && SiteSetting.default_theme_id != -1
-    theme_id = nil if theme_id.blank? || theme_id == -1
+      theme_ids << SiteSetting.default_theme_id
+    end
 
-    @theme_id = request.env[:resolved_theme_id] = theme_id
+    @theme_ids = request.env[:resolved_theme_ids] = theme_ids
   end
 
   def guardian
@@ -502,10 +507,10 @@ class ApplicationController < ActionController::Base
     target = view_context.mobile_view? ? :mobile : :desktop
 
     data =
-      if @theme_id
+      if @theme_ids.present?
         {
-         top: Theme.lookup_field(@theme_id, target, "after_header"),
+         top: Theme.lookup_field(@theme_ids, target, "after_header"),
-         footer: Theme.lookup_field(@theme_id, target, "footer")
+         footer: Theme.lookup_field(@theme_ids, target, "footer")
         }
       else
         {}

app/controllers/stylesheets_controller.rb

@@ -29,7 +29,7 @@ class StylesheetsController < ApplicationController
       # we hold of re-compilation till someone asks for asset
       if target.include?("theme")
         split_target, theme_id = target.split(/_(-?[0-9]+)/)
-        theme = Theme.find(theme_id) if theme_id
+        theme = Theme.find_by(id: theme_id) if theme_id.present?
       else
         split_target, color_scheme_id = target.split(/_(-?[0-9]+)/)
         theme = Theme.find_by(color_scheme_id: color_scheme_id)

app/controllers/themes_controller.rb

@@ -1,27 +1,26 @@
 class ThemesController < ::ApplicationController
   def assets
-    theme_id = params[:id].to_i
+    theme_ids = params[:ids].to_s.split("-").map(&:to_i)
 
-    if params[:id] == "default"
+    if params[:ids] == "default"
-      theme_id = nil
+      theme_ids = nil
     else
-      raise Discourse::NotFound unless Theme.where(id: theme_id).exists?
+      raise Discourse::NotFound unless guardian.allow_themes?(theme_ids)
     end
 
-    object = [:mobile, :desktop, :desktop_theme, :mobile_theme].map do |target|
+    targets = view_context.mobile_view? ? [:mobile, :mobile_theme] : [:desktop, :desktop_theme]
-      link = Stylesheet::Manager.stylesheet_link_tag(target, 'all', params[:id])
+    targets << :admin if guardian.is_staff?
-      if link
+
-        href = link.split(/["']/)[1]
+    object = targets.map do |target|
-        if Rails.env.development?
+      Stylesheet::Manager.stylesheet_data(target, theme_ids).map do |hash|
-          href << (href.include?("?") ? "&" : "?")
+        return hash unless Rails.env.development?
-          href << SecureRandom.hex
+
-        end
+        dup_hash = hash.dup
-        {
+        dup_hash[:new_href] << (dup_hash[:new_href].include?("?") ? "&" : "?")
-          target: target,
+        dup_hash[:new_href] << SecureRandom.hex
-          url: href
+        dup_hash
-        }
       end
-    end.compact
+    end.flatten
 
     render json: object.as_json
   end

app/helpers/application_helper.rb

@@ -350,11 +350,11 @@ module ApplicationHelper
     end
   end
 
-  def theme_id
+  def theme_ids
     if customization_disabled?
       nil
     else
-      request.env[:resolved_theme_id]
+      request.env[:resolved_theme_ids]
     end
   end
 
@@ -378,17 +378,17 @@ module ApplicationHelper
   end
 
   def theme_lookup(name)
-    lookup = Theme.lookup_field(theme_id, mobile_view? ? :mobile : :desktop, name)
+    lookup = Theme.lookup_field(theme_ids, mobile_view? ? :mobile : :desktop, name)
     lookup.html_safe if lookup
   end
 
   def discourse_stylesheet_link_tag(name, opts = {})
-    if opts.key?(:theme_id)
+    if opts.key?(:theme_ids)
-      id = opts[:theme_id] unless customization_disabled?
+      ids = opts[:theme_ids] unless customization_disabled?
     else
-      id = theme_id
+      ids = theme_ids
     end
 
-    Stylesheet::Manager.stylesheet_link_tag(name, 'all', id)
+    Stylesheet::Manager.stylesheet_link_tag(name, 'all', ids)
   end
 end

app/models/child_theme.rb

@@ -1,6 +1,24 @@
 class ChildTheme < ActiveRecord::Base
   belongs_to :parent_theme, class_name: 'Theme'
   belongs_to :child_theme, class_name: 'Theme'
+
+  validate :child_validations
+
+  private
+
+  def child_validations
+    if ChildTheme.exists?(["parent_theme_id = ? OR child_theme_id = ?", child_theme_id, parent_theme_id])
+      errors.add(:base, I18n.t("themes.errors.no_multilevels_components"))
+    end
+
+    if Theme.exists?(id: child_theme_id, user_selectable: true)
+      errors.add(:base, I18n.t("themes.errors.component_no_user_selectable"))
+    end
+
+    if child_theme_id == SiteSetting.default_theme_id
+      errors.add(:base, I18n.t("themes.errors.component_no_default"))
+    end
+  end
 end
 
 # == Schema Information

app/models/color_scheme.rb

@@ -241,12 +241,15 @@ class ColorScheme < ActiveRecord::Base
 
   def publish_discourse_stylesheet
     if self.id
-      themes = Theme.where(color_scheme_id: self.id).to_a
+      theme_ids = Theme.where(color_scheme_id: self.id).pluck(:id)
-      if themes.present?
+      if theme_ids.present?
         Stylesheet::Manager.cache.clear
-        themes.each do |theme|
+        Theme.notify_theme_change(
-          theme.notify_scheme_change(_clear_manager_cache = false)
+          theme_ids,
-        end
+          with_scheme: true,
+          clear_manager_cache: false,
+          all_themes: true
+        )
       end
     end
   end

app/models/theme.rb

@@ -20,6 +20,12 @@ class Theme < ActiveRecord::Base
   has_many :color_schemes
   belongs_to :remote_theme
 
+  validate :user_selectable_validation
+
+  scope :user_selectable, ->() {
+    where('user_selectable OR id = ?', SiteSetting.default_theme_id)
+  }
+
   def notify_color_change(color)
     changed_colors << color
   end
@@ -45,7 +51,6 @@ class Theme < ActiveRecord::Base
 
     remove_from_cache!
     clear_cached_settings!
-    notify_scheme_change if saved_change_to_color_scheme_id?
   end
 
   after_destroy do
@@ -70,29 +75,37 @@ class Theme < ActiveRecord::Base
   end
 
   after_commit ->(theme) do
-    theme.notify_theme_change
+    theme.notify_theme_change(with_scheme: theme.saved_change_to_color_scheme_id?)
-  end, on: :update
+  end, on: [:create, :update]
+
+  def self.get_set_cache(key, &blk)
+    if val = @cache[key]
+      return val
+    end
+    @cache[key] = blk.call
+  end
 
   def self.theme_ids
-    if ids = @cache["theme_ids"]
+    get_set_cache "theme_ids" do
-      return ids
+      Theme.pluck(:id)
     end
-    @cache["theme_ids"] = Set.new(Theme.pluck(:id))
   end
 
   def self.user_theme_ids
-    if ids = @cache["user_theme_ids"]
+    get_set_cache "user_theme_ids" do
-      return ids
+      Theme.user_selectable.pluck(:id)
+    end
+  end
+
+  def self.components_for(theme_id)
+    get_set_cache "theme_components_for_#{theme_id}" do
+      ChildTheme.where(parent_theme_id: theme_id).distinct.pluck(:child_theme_id)
     end
-    @cache["user_theme_ids"] = Set.new(
-      Theme
-      .where('user_selectable OR id = ?', SiteSetting.default_theme_id)
-      .pluck(:id)
-    )
   end
 
   def self.expire_site_cache!
     Site.clear_anon_cache!
+    clear_cache!
     ApplicationSerializer.expire_cache_fragment!("user_themes")
   end
 
@@ -101,7 +114,25 @@ class Theme < ActiveRecord::Base
     expire_site_cache!
   end
 
+  def self.transform_ids(ids, extend: true)
+    return [] if ids.blank?
+
+    ids.uniq!
+    parent = ids.first
+
+    components = ids[1..-1]
+    components.push(*components_for(parent)) if extend
+    components.sort!.uniq!
+
+    [parent, *components]
+  end
+
   def set_default!
+    if component?
+      raise Discourse::InvalidParameters.new(
+        I18n.t("themes.errors.component_no_default")
+      )
+    end
     SiteSetting.default_theme_id = id
     Theme.expire_site_cache!
   end
@@ -110,22 +141,32 @@ class Theme < ActiveRecord::Base
     SiteSetting.default_theme_id == id
   end
 
-  def self.lookup_field(theme_id, target, field)
+  def component?
-    return if theme_id.blank?
+    ChildTheme.exists?(child_theme_id: id)
+  end
 
-    cache_key = "#{theme_id}:#{target}:#{field}:#{ThemeField::COMPILER_VERSION}"
+  def user_selectable_validation
+    if component? && user_selectable
+      errors.add(:base, I18n.t("themes.errors.component_no_user_selectable"))
+    end
+  end
+
+  def self.lookup_field(theme_ids, target, field)
+    return if theme_ids.blank?
+    theme_ids = [theme_ids] unless Array === theme_ids
+
+    theme_ids = transform_ids(theme_ids)
+    cache_key = "#{theme_ids.join(",")}:#{target}:#{field}:#{ThemeField::COMPILER_VERSION}"
     lookup = @cache[cache_key]
     return lookup.html_safe if lookup
 
     target = target.to_sym
-    theme = find_by(id: theme_id)
+    val = resolve_baked_field(theme_ids, target, field)
-
-    val = theme.resolve_baked_field(target, field) if theme
 
     (@cache[cache_key] = val || "").html_safe
   end
 
-  def self.remove_from_cache!(themes = nil)
+  def self.remove_from_cache!
     clear_cache!
   end
 
@@ -141,33 +182,32 @@ class Theme < ActiveRecord::Base
     self.targets.invert[target_id]
   end
 
-  def notify_scheme_change(clear_manager_cache = true)
+  def self.notify_theme_change(theme_ids, with_scheme: false, clear_manager_cache: true, all_themes: false)
-    Stylesheet::Manager.cache.clear if clear_manager_cache
-    message = refresh_message_for_targets(["desktop", "mobile", "admin"], self)
-    MessageBus.publish('/file-change', message)
-  end
-
-  def notify_theme_change
     Stylesheet::Manager.clear_theme_cache!
+    targets = [:mobile_theme, :desktop_theme]
 
-    themes = [self] + dependant_themes
+    if with_scheme
+      targets.prepend(:desktop, :mobile, :admin)
+      Stylesheet::Manager.cache.clear if clear_manager_cache
+    end
+
+    if all_themes
+      message = theme_ids.map { |id| refresh_message_for_targets(targets, id) }.flatten
+    else
+      message = refresh_message_for_targets(targets, theme_ids).flatten
+    end
 
-    message = themes.map do |theme|
-      refresh_message_for_targets([:mobile_theme, :desktop_theme], theme)
-    end.compact.flatten
     MessageBus.publish('/file-change', message)
   end
 
-  def refresh_message_for_targets(targets, theme)
+  def notify_theme_change(with_scheme: false)
+    theme_ids = (dependant_themes&.pluck(:id) || []).unshift(self.id)
+    self.class.notify_theme_change(theme_ids, with_scheme: with_scheme)
+  end
+
+  def self.refresh_message_for_targets(targets, theme_ids)
     targets.map do |target|
-      href = Stylesheet::Manager.stylesheet_href(target.to_sym, theme.id)
+      Stylesheet::Manager.stylesheet_data(target.to_sym, theme_ids)
-      if href
-        {
-          target: target,
-          new_href: href,
-          theme_id: theme.id
-        }
-      end
     end
   end
 
@@ -180,48 +220,34 @@ class Theme < ActiveRecord::Base
   end
 
   def resolve_dependant_themes(direction)
-
-    select_field, where_field = nil
-
     if direction == :up
-      select_field = "parent_theme_id"
+      join_field = "parent_theme_id"
       where_field = "child_theme_id"
     elsif direction == :down
-      select_field = "child_theme_id"
+      join_field = "child_theme_id"
       where_field = "parent_theme_id"
     else
       raise "Unknown direction"
     end
 
-    themes = []
     return [] unless id
 
-    uniq = Set.new
+    Theme.joins("JOIN child_themes ON themes.id = child_themes.#{join_field}").where("#{where_field} = ?", id)
-    uniq << id
+  end
 
-    iterations = 0
+  def self.resolve_baked_field(theme_ids, target, name)
-    added = [id]
+    list_baked_fields(theme_ids, target, name).map { |f| f.value_baked || f.value }.join("\n")
+  end
 
-    while added.length > 0 && iterations < 5
+  def self.list_baked_fields(theme_ids, target, name)
+    target = target.to_sym
 
-      iterations += 1
+    fields = ThemeField.find_by_theme_ids(theme_ids)
+      .where(target_id: [Theme.targets[target], Theme.targets[:common]])
+      .where(name: name.to_s)
 
-      new_themes = Theme.where("id in (SELECT #{select_field}
+    fields.each(&:ensure_baked!)
-                                  FROM child_themes
+    fields
-                                  WHERE #{where_field} in (?))", added).to_a
-
-      added = []
-      new_themes.each do |theme|
-        unless uniq.include?(theme.id)
-          added << theme.id
-          uniq << theme.id
-          themes << theme
-        end
-      end
-
-    end
-
-    themes
   end
 
   def resolve_baked_field(target, name)
@@ -229,22 +255,8 @@ class Theme < ActiveRecord::Base
   end
 
   def list_baked_fields(target, name)
-
+    theme_ids = (included_themes&.pluck(:id) || []).unshift(self.id)
-    target = target.to_sym
+    self.class.list_baked_fields(theme_ids, target, name)
-
-    theme_ids = [self.id] + (included_themes.map(&:id) || [])
-    fields = ThemeField.where(target_id: [Theme.targets[target], Theme.targets[:common]])
-      .where(name: name.to_s)
-      .includes(:theme)
-      .joins("
-        JOIN (
-          SELECT #{theme_ids.map.with_index { |id, idx| "#{id} AS theme_id, #{idx} AS sort_column" }.join(" UNION ALL SELECT ")}
-        ) as X ON X.theme_id = theme_fields.theme_id"
-      )
-      .order('sort_column, target_id')
-
-    fields.each(&:ensure_baked!)
-    fields
   end
 
   def remove_from_cache!
@@ -288,21 +300,23 @@ class Theme < ActiveRecord::Base
 
   def all_theme_variables
     fields = {}
-    ([self] + (included_themes || [])).each do |theme|
+    ids = (included_themes&.pluck(:id) || []).unshift(self.id)
-      theme&.theme_fields.each do |field|
+    ThemeField.find_by_theme_ids(ids).where(type_id: ThemeField.theme_var_type_ids).each do |field|
-        next unless ThemeField.theme_var_type_ids.include?(field.type_id)
+      next if fields.key?(field.name)
-        next if fields.key?(field.name)
+      fields[field.name] = field
-        fields[field.name] = field
-      end
     end
     fields.values
   end
 
   def add_child_theme!(theme)
-    child_theme_relation.create!(child_theme_id: theme.id)
+    new_relation = child_theme_relation.new(child_theme_id: theme.id)
-    @included_themes = nil
+    if new_relation.save
-    child_themes.reload
+      @included_themes = nil
-    save!
+      child_themes.reload
+      save!
+    else
+      raise Discourse::InvalidParameters.new(new_relation.errors.full_messages.join(", "))
+    end
   end
 
   def settings

app/models/theme_field.rb

@@ -4,6 +4,17 @@ class ThemeField < ActiveRecord::Base
 
   belongs_to :upload
 
+  scope :find_by_theme_ids, ->(theme_ids) {
+    return none unless theme_ids.present?
+
+    where(theme_id: theme_ids)
+      .joins(
+        "JOIN (
+          SELECT #{theme_ids.map.with_index { |id, idx| "#{id.to_i} AS theme_id, #{idx} AS sort_column" }.join(" UNION ALL SELECT ")}
+        ) as X ON X.theme_id = theme_fields.theme_id")
+      .order("sort_column")
+  }
+
   def self.types
     @types ||= Enum.new(html: 0,
                         scss: 1,

app/views/common/_discourse_stylesheet.html.erb

@@ -8,6 +8,6 @@
   <%= discourse_stylesheet_link_tag(:admin) %>
 <%- end %>
 
-<%- if theme_id %>
+<%- if theme_ids.present? %>
   <%= discourse_stylesheet_link_tag(mobile_view? ? :mobile_theme : :desktop_theme) %>
 <%- end %>

app/views/layouts/application.html.erb

@@ -4,7 +4,7 @@
     <meta charset="utf-8">
     <title><%= content_for?(:title) ? yield(:title) : SiteSetting.title %></title>
     <meta name="description" content="<%= @description_meta || SiteSetting.site_description %>">
-    <meta name="discourse_theme_id" content="<%= theme_id %>">
+    <meta name="discourse_theme_ids" content="<%= theme_ids&.join(",") %>">
     <meta name="discourse_current_homepage" content="<%= current_homepage %>">
     <%= render partial: "layouts/head" %>
     <%= discourse_csrf_tags %>

app/views/layouts/crawler.html.erb

@@ -10,7 +10,7 @@
     <%- else %>
       <%= discourse_stylesheet_link_tag(mobile_view? ? :mobile : :desktop) %>
     <%- end %>
-    <%- if theme_id %>
+    <%- if theme_ids.present? %>
       <%= discourse_stylesheet_link_tag(mobile_view? ? :mobile_theme : :desktop_theme) %>
     <%- end %>
     <%= theme_lookup("head_tag") %>

app/views/layouts/embed.html.erb

@@ -3,7 +3,7 @@
   <head>
     <meta charset="utf-8">
 
-    <%= discourse_stylesheet_link_tag 'embed', theme_id: nil %>
+    <%= discourse_stylesheet_link_tag 'embed', theme_ids: nil %>
     <%- unless customization_disabled? %>
       <%= discourse_stylesheet_link_tag  :embedded_theme %>
     <%- end %>

app/views/layouts/finish_installation.html.erb

@@ -1,6 +1,6 @@
 <html>
   <head>
-    <%= discourse_stylesheet_link_tag 'wizard', theme_id: nil %>
+    <%= discourse_stylesheet_link_tag 'wizard', theme_ids: nil %>
     <%= render partial: "common/special_font_face" %>
     <%= preload_script 'ember_jquery' %>
     <%= preload_script 'wizard-vendor' %>

app/views/wizard/index.html.erb

@@ -1,6 +1,6 @@
 <html>
   <head>
-    <%= discourse_stylesheet_link_tag :wizard, theme_id: nil %>
+    <%= discourse_stylesheet_link_tag :wizard, theme_ids: nil %>
     <%= preload_script 'ember_jquery' %>
     <%= preload_script 'wizard-vendor' %>
     <%= preload_script 'wizard-application' %>

app/views/wizard/qunit.html.erb

@@ -4,7 +4,7 @@
     <title>QUnit Test Runner</title>
     <%= stylesheet_link_tag "qunit" %>
     <%= stylesheet_link_tag "test_helper" %>
-    <%= discourse_stylesheet_link_tag :wizard %>
+    <%= discourse_stylesheet_link_tag :wizard, theme_ids: nil %>
     <%= javascript_include_tag "qunit" %>
     <%= javascript_include_tag "wizard/test/test_helper" %>
     <%= csrf_meta_tags %>

config/locales/server.en.yml

@@ -60,6 +60,10 @@ en:
     bad_color_scheme: "Can not update theme, invalid color scheme"
     other_error: "Something went wrong updating theme"
     error_importing: "Error cloning git repository, access is denied or repository is not found"
+    errors:
+      component_no_user_selectable: "Theme components can't be user-selectable"
+      component_no_default: "Theme components can't be default theme"
+      no_multilevels_components: "Themes with child themes can't be child themes themselves"
     settings_errors:
       invalid_yaml: "Provided YAML is invalid."
       data_type_not_a_number: "Setting `%{name}` type is unsupported. Supported types are `integer`, `bool`, `list` and `enum`"

config/routes.rb

@@ -814,7 +814,7 @@ Discourse::Application.routes.draw do
   get "/safe-mode" => "safe_mode#index"
   post "/safe-mode" => "safe_mode#enter", as: "safe_mode_enter"
 
-  get "/themes/assets/:id" => "themes#assets"
+  get "/themes/assets/:ids" => "themes#assets"
 
   if Rails.env == "test" || Rails.env == "development"
     get "/qunit" => "qunit#index"

db/migrate/20180710172959_disallow_multi_levels_theme_components.rb

@@ -0,0 +1,68 @@
+class DisallowMultiLevelsThemeComponents < ActiveRecord::Migration[5.2]
+  def up
+    @handled = []
+    top_parents = DB.query("
+      SELECT parent_theme_id, child_theme_id
+      FROM child_themes
+      WHERE parent_theme_id NOT IN (SELECT child_theme_id FROM child_themes)
+    ")
+
+    top_parents.each do |top_parent|
+      migrate_child(top_parent, top_parent)
+    end
+
+    if @handled.size > 0
+      execute("
+        DELETE FROM child_themes
+        WHERE parent_theme_id NOT IN (#{top_parents.map(&:parent_theme_id).join(", ")})
+      ")
+    end
+
+    execute("
+      UPDATE themes
+      SET user_selectable = false
+      FROM child_themes
+      WHERE themes.id = child_themes.child_theme_id
+      AND themes.user_selectable = true
+    ")
+
+    default = DB.query_single("SELECT value FROM site_settings WHERE name = 'default_theme_id'").first
+    if default
+      default_child = DB.query("SELECT 1 AS one FROM child_themes WHERE child_theme_id = ?", default.to_i).present?
+      execute("DELETE FROM site_settings WHERE name = 'default_theme_id'") if default_child
+    end
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+
+  private
+
+  def migrate_child(parent, top_parent)
+    unless already_exists?(top_parent.parent_theme_id, parent.child_theme_id)
+      execute("
+        INSERT INTO child_themes (parent_theme_id, child_theme_id, created_at, updated_at)
+        VALUES (#{top_parent.parent_theme_id}, #{parent.child_theme_id}, now(), now())
+      ")
+    end
+
+    @handled << [top_parent.parent_theme_id, parent.parent_theme_id, parent.child_theme_id]
+
+    children = DB.query("
+      SELECT parent_theme_id, child_theme_id
+      FROM child_themes
+      WHERE parent_theme_id = :child", child: parent.child_theme_id
+    )
+
+    children.each do |child|
+      unless @handled.include?([top_parent.parent_theme_id, child.parent_theme_id, child.child_theme_id])
+        migrate_child(child, top_parent)
+      end
+    end
+  end
+
+  def already_exists?(parent, child)
+    DB.query("SELECT 1 AS one FROM child_themes WHERE child_theme_id = :child AND parent_theme_id = :parent", child: child, parent: parent).present?
+  end
+end

lib/guardian.rb

@@ -359,9 +359,15 @@ class Guardian
   end
 
   def allow_themes?(theme_ids)
-    theme_ids = [theme_ids] unless theme_ids.is_a?(Array)
+    if is_staff? && (theme_ids - Theme.theme_ids).blank?
-    allowed_ids = is_staff? ? Theme.theme_ids : Theme.user_theme_ids
+      return true
-    (theme_ids - allowed_ids.to_a).empty?
+    end
+
+    parent = theme_ids.first
+    components = theme_ids[1..-1] || []
+
+    Theme.user_theme_ids.include?(parent) &&
+      (components - Theme.components_for(parent)).empty?
   end
 
   private

lib/middleware/anonymous_cache.rb

@@ -66,16 +66,16 @@ module Middleware
       end
 
       def cache_key
-        @cache_key ||= "ANON_CACHE_#{@env["HTTP_ACCEPT"]}_#{@env["HTTP_HOST"]}#{@env["REQUEST_URI"]}|m=#{is_mobile?}|c=#{is_crawler?}|b=#{has_brotli?}|t=#{theme_id}"
+        @cache_key ||= "ANON_CACHE_#{@env["HTTP_ACCEPT"]}_#{@env["HTTP_HOST"]}#{@env["REQUEST_URI"]}|m=#{is_mobile?}|c=#{is_crawler?}|b=#{has_brotli?}|t=#{theme_ids.join(",")}"
       end
 
-      def theme_id
+      def theme_ids
         ids, _ = @request.cookies['theme_ids']&.split('|')
         ids = ids&.split(",")&.map(&:to_i)
         if ids && Guardian.new.allow_themes?(ids)
-          ids.first
+          Theme.transform_ids(ids)
         else
-          nil
+          []
         end
       end
 

lib/stylesheet/manager.rb

@@ -8,6 +8,7 @@ class Stylesheet::Manager
   CACHE_PATH ||= 'tmp/stylesheet-cache'
   MANIFEST_DIR ||= "#{Rails.root}/tmp/cache/assets/#{Rails.env}"
   MANIFEST_FULL_PATH ||= "#{MANIFEST_DIR}/stylesheet-manifest"
+  THEME_REGEX ||= /_theme$/
 
   @lock = Mutex.new
 
@@ -19,38 +20,65 @@ class Stylesheet::Manager
     cache.hash.keys.select { |k| k =~ /theme/ }.each { |k|cache.delete(k) }
   end
 
-  def self.stylesheet_href(target = :desktop, theme_id = :missing)
+  def self.stylesheet_data(target = :desktop, theme_ids = :missing)
-    href = stylesheet_link_tag(target, 'all', theme_id)
+    stylesheet_details(target, "all", theme_ids)
-    if href
-      href.split(/["']/)[1]
-    end
   end
 
-  def self.stylesheet_link_tag(target = :desktop, media = 'all', theme_id = :missing)
+  def self.stylesheet_link_tag(target = :desktop, media = 'all', theme_ids = :missing)
+    stylesheets = stylesheet_details(target, media, theme_ids)
+    stylesheets.map do |stylesheet|
+      href = stylesheet[:new_href]
+      theme_id = stylesheet[:theme_id]
+      data_theme_id = theme_id ? "data-theme-id=\"#{theme_id}\"" : ""
+      %[<link href="#{href}" media="#{media}" rel="stylesheet" data-target="#{target}" #{data_theme_id}/>]
+    end.join("\n").html_safe
+  end
+
+  def self.stylesheet_details(target = :desktop, media = 'all', theme_ids = :missing)
+    if theme_ids == :missing
+      theme_ids = [SiteSetting.default_theme_id]
+    end
 
     target = target.to_sym
 
-    if theme_id == :missing
+    theme_ids = [theme_ids] unless Array === theme_ids
-      theme_id = SiteSetting.default_theme_id
+    theme_ids = [theme_ids.first] unless target =~ THEME_REGEX
-    end
+    theme_ids = Theme.transform_ids(theme_ids, extend: false)
 
     current_hostname = Discourse.current_hostname
-    cache_key = "#{target}_#{theme_id}_#{current_hostname}"
-    tag = cache[cache_key]
 
-    return tag.dup.html_safe if tag
+    array_cache_key = "array_themes_#{theme_ids.join(",")}_#{target}_#{current_hostname}"
+    stylesheets = cache[array_cache_key]
+    return stylesheets if stylesheets.present?
 
     @lock.synchronize do
-      builder = self.new(target, theme_id)
+      stylesheets = []
-      if builder.is_theme? && !builder.theme
+      theme_ids.each do |theme_id|
-        tag = ""
+        data = { target: target }
-      else
+        cache_key = "path_#{target}_#{theme_id}_#{current_hostname}"
-        builder.compile unless File.exists?(builder.stylesheet_fullpath)
+        href = cache[cache_key]
-        tag = %[<link href="#{builder.stylesheet_path(current_hostname)}" media="#{media}" rel="stylesheet" data-target="#{target}"/>]
-      end
 
-      cache[cache_key] = tag
+        unless href
-      tag.dup.html_safe
+          builder = self.new(target, theme_id)
+          is_theme = builder.is_theme?
+          has_theme = builder.theme.present?
+
+          if is_theme && !has_theme
+            next
+          else
+            data[:theme_id] = builder.theme.id if has_theme && is_theme
+            builder.compile unless File.exists?(builder.stylesheet_fullpath)
+            href = builder.stylesheet_path(current_hostname)
+          end
+          cache[cache_key] = href
+        end
+
+        data[:theme_id] = theme_id if theme_id.present? && data[:theme_id].blank?
+        data[:new_href] = href
+        stylesheets << data
+      end
+      cache[array_cache_key] = stylesheets.freeze
+      stylesheets
     end
   end
 
@@ -100,6 +128,10 @@ class Stylesheet::Manager
     end.compact.max.to_i
   end
 
+  def self.cache_fullpath
+    "#{Rails.root}/#{CACHE_PATH}"
+  end
+
   def initialize(target = :desktop, theme_id)
     @target = target
     @theme_id = theme_id
@@ -162,10 +194,6 @@ class Stylesheet::Manager
     css
   end
 
-  def self.cache_fullpath
-    "#{Rails.root}/#{CACHE_PATH}"
-  end
-
   def cache_fullpath
     self.class.cache_fullpath
   end
@@ -225,7 +253,7 @@ class Stylesheet::Manager
   end
 
   def is_theme?
-    !!(@target.to_s =~ /_theme$/)
+    !!(@target.to_s =~ THEME_REGEX)
   end
 
   # digest encodes the things that trigger a recompile
@@ -240,7 +268,7 @@ class Stylesheet::Manager
   end
 
   def theme
-    @theme ||= (Theme.find_by(id: @theme_id) || :nil)
+    @theme ||= Theme.find_by(id: @theme_id) || :nil
     @theme == :nil ? nil : @theme
   end
 
@@ -271,7 +299,16 @@ class Stylesheet::Manager
   end
 
   def settings_digest
-    Digest::SHA1.hexdigest((theme&.included_settings || {}).to_json)
+    fields = ThemeField.where(
+      name: "yaml",
+      type_id: ThemeField.types[:yaml],
+      theme_id: @theme_id
+    ).pluck(:updated_at)
+
+    settings = ThemeSetting.where(theme_id: @theme_id).pluck(:updated_at)
+    timestamps = fields.concat(settings).map!(&:to_f).sort!.join(",")
+
+    Digest::SHA1.hexdigest(timestamps)
   end
 
   def uploads_digest

lib/stylesheet/watcher.rb

@@ -8,7 +8,10 @@ module Stylesheet
     end
 
     def self.theme_id
-      @theme_id || SiteSetting.default_theme_id
+      if @theme_id.blank? && SiteSetting.default_theme_id != -1
+        @theme_id = SiteSetting.default_theme_id
+      end
+      @theme_id
     end
 
     def self.watch(paths = nil)
@@ -76,12 +79,8 @@ module Stylesheet
       Stylesheet::Manager.cache.clear
 
       message = ["desktop", "mobile", "admin"].map do |name|
-        {
+        Stylesheet::Manager.stylesheet_data(name.to_sym, Stylesheet::Watcher.theme_id)
-          target: name,
+      end.flatten
-          new_href: Stylesheet::Manager.stylesheet_href(name.to_sym),
-          theme_id: Stylesheet::Watcher.theme_id
-        }
-      end
       MessageBus.publish '/file-change', message
     end
 

spec/components/guardian_spec.rb

@@ -2537,6 +2537,46 @@ describe Guardian do
     end
   end
 
+  describe "#allow_themes?" do
+    let(:theme) { Fabricate(:theme) }
+    let(:theme2) { Fabricate(:theme) }
+
+    it "allows staff to use any themes" do
+      expect(Guardian.new(moderator).allow_themes?([theme.id, theme2.id])).to eq(true)
+      expect(Guardian.new(admin).allow_themes?([theme.id, theme2.id])).to eq(true)
+    end
+
+    it "only allows normal users to use user-selectable themes or default theme" do
+      user_guardian = Guardian.new(user)
+
+      expect(user_guardian.allow_themes?([theme.id, theme2.id])).to eq(false)
+      expect(user_guardian.allow_themes?([theme.id])).to eq(false)
+      expect(user_guardian.allow_themes?([theme2.id])).to eq(false)
+
+      theme.set_default!
+      expect(user_guardian.allow_themes?([theme.id])).to eq(true)
+      expect(user_guardian.allow_themes?([theme2.id])).to eq(false)
+      expect(user_guardian.allow_themes?([theme.id, theme2.id])).to eq(false)
+
+      theme2.update!(user_selectable: true)
+      expect(user_guardian.allow_themes?([theme2.id])).to eq(true)
+      expect(user_guardian.allow_themes?([theme2.id, theme.id])).to eq(false)
+    end
+
+    it "allows child themes to be only used with their parent" do
+      user_guardian = Guardian.new(user)
+
+      theme.update!(user_selectable: true)
+      theme2.update!(user_selectable: true)
+      expect(user_guardian.allow_themes?([theme.id, theme2.id])).to eq(false)
+
+      theme2.update!(user_selectable: false)
+      theme.add_child_theme!(theme2)
+      expect(user_guardian.allow_themes?([theme.id, theme2.id])).to eq(true)
+      expect(user_guardian.allow_themes?([theme2.id])).to eq(false)
+    end
+  end
+
   describe 'can_wiki?' do
     let(:post) { build(:post, created_at: 1.minute.ago) }
 

spec/components/middleware/anonymous_cache_spec.rb

@@ -32,7 +32,7 @@ describe Middleware::AnonymousCache::Helper do
 
   context "per theme cache" do
     it "handles theme keys" do
-      theme = Theme.create(name: "test", user_id: -1, user_selectable: true)
+      theme = Fabricate(:theme, user_selectable: true)
 
       with_bad_theme_key = new_helper("HTTP_COOKIE" => "theme_ids=abc").cache_key
       with_no_theme_key = new_helper().cache_key

spec/components/stylesheet/manager_spec.rb

@@ -8,7 +8,7 @@ describe Stylesheet::Manager do
     link = Stylesheet::Manager.stylesheet_link_tag(:embedded_theme)
     expect(link).to eq("")
 
-    theme = Theme.create(name: "embedded", user_id: -1)
+    theme = Fabricate(:theme)
     SiteSetting.default_theme_id = theme.id
 
     link = Stylesheet::Manager.stylesheet_link_tag(:embedded_theme)
@@ -16,10 +16,7 @@ describe Stylesheet::Manager do
   end
 
   it 'can correctly compile theme css' do
-    theme = Theme.new(
+    theme = Fabricate(:theme)
-      name: 'parent',
-      user_id: -1
-    )
 
     theme.set_field(target: :common, name: "scss", value: ".common{.scss{color: red;}}")
     theme.set_field(target: :desktop, name: "scss", value: ".desktop{.scss{color: red;}}")
@@ -28,10 +25,7 @@ describe Stylesheet::Manager do
 
     theme.save!
 
-    child_theme = Theme.new(
+    child_theme = Fabricate(:theme)
-      name: 'parent',
-      user_id: -1,
-    )
 
     child_theme.set_field(target: :common, name: "scss", value: ".child_common{.scss{color: red;}}")
     child_theme.set_field(target: :desktop, name: "scss", value: ".child_desktop{.scss{color: red;}}")
@@ -72,10 +66,7 @@ describe Stylesheet::Manager do
 
     it 'can correctly account for plugins in digest' do
 
-      theme = Theme.create!(
+      theme = Fabricate(:theme)
-        name: 'parent',
-        user_id: -1
-      )
 
       manager = Stylesheet::Manager.new(:desktop_theme, theme.id)
       digest1 = manager.digest
@@ -92,10 +83,7 @@ describe Stylesheet::Manager do
     let(:image2) { file_from_fixtures("logo-dev.png") }
 
     it 'can correctly account for theme uploads in digest' do
-      theme = Theme.create!(
+      theme = Fabricate(:theme)
-        name: 'parent',
-        user_id: -1
-      )
 
       upload = UploadCreator.new(image, "logo.png").create_for(-1)
       field = ThemeField.create!(
@@ -130,10 +118,7 @@ describe Stylesheet::Manager do
 
   describe 'color_scheme_digest' do
     it "changes with category background image" do
-      theme = Theme.new(
+      theme = Fabricate(:theme)
-        name: 'parent',
-        user_id: -1
-      )
       category1 = Fabricate(:category, uploaded_background_id: 123, updated_at: 1.week.ago)
       category2 = Fabricate(:category, uploaded_background_id: 456, updated_at: 2.days.ago)
 

spec/components/theme_settings_manager_spec.rb

@@ -4,7 +4,7 @@ require 'theme_settings_manager'
 describe ThemeSettingsManager do
 
   let(:theme_settings) do
-    theme = Theme.create!(name: "awesome theme", user_id: -1)
+    theme = Fabricate(:theme)
     yaml = File.read("#{Rails.root}/spec/fixtures/theme_settings/valid_settings.yaml")
     theme.set_field(target: :settings, name: "yaml", value: yaml)
     theme.save!

spec/components/wizard/step_updater_spec.rb

@@ -194,6 +194,7 @@ describe Wizard::StepUpdater do
 
     context "without an existing scheme" do
       it "creates the scheme" do
+        ColorScheme.destroy_all
         updater = wizard.create_updater('colors', theme_previews: 'Dark', allow_dark_light_selection: true)
         updater.update
         expect(updater.success?).to eq(true)

spec/fabricators/theme_fabricator.rb

@@ -0,0 +1,4 @@
+Fabricator(:theme) do
+  name { sequence(:name) { |i| "Cool theme #{i + 1}" } }
+  user
+end

spec/mailers/user_notifications_spec.rb

@@ -191,12 +191,12 @@ describe UserNotifications do
           Fabricate(:color_scheme_color, name: 'header_background', hex: '1E1E1E'),
           Fabricate(:color_scheme_color, name: 'tertiary', hex: '858585')
         ])
-        theme = Theme.create!(
+        theme = Fabricate(:theme,
-          name: 'my name',
-          user_id: Fabricate(:admin).id,
           user_selectable: true,
+          user: Fabricate(:admin),
           color_scheme_id: cs.id
         )
+
         theme.set_default!
 
         html = subject.html_part.body.to_s

spec/models/admin_dashboard_data_spec.rb

@@ -338,7 +338,7 @@ describe AdminDashboardData do
 
   describe '#out_of_date_themes' do
     let(:remote) { RemoteTheme.create!(remote_url: "https://github.com/org/testtheme") }
-    let!(:theme) { Theme.create!(remote_theme_id: remote.id, name: "Test< Theme", user_id: -1) }
+    let!(:theme) { Fabricate(:theme, remote_theme: remote, name: "Test< Theme") }
 
     it "outputs correctly formatted html" do
       remote.update!(local_version: "old version", remote_version: "new version", commits_behind: 2)

spec/models/child_theme_spec.rb

@@ -0,0 +1,43 @@
+require 'rails_helper'
+
+describe ChildTheme do
+  describe "validations" do
+    it "doesn't allow children to become parents or parents to become children" do
+      theme = Fabricate(:theme)
+      child = Fabricate(:theme)
+
+      child_theme = ChildTheme.new(parent_theme: theme, child_theme: child)
+      expect(child_theme.valid?).to eq(true)
+      child_theme.save!
+
+      grandchild = Fabricate(:theme)
+      child_theme = ChildTheme.new(parent_theme: child, child_theme: grandchild)
+      expect(child_theme.valid?).to eq(false)
+      expect(child_theme.errors.full_messages).to contain_exactly(I18n.t("themes.errors.no_multilevels_components"))
+
+      grandparent = Fabricate(:theme)
+      child_theme = ChildTheme.new(parent_theme: grandparent, child_theme: theme)
+      expect(child_theme.valid?).to eq(false)
+      expect(child_theme.errors.full_messages).to contain_exactly(I18n.t("themes.errors.no_multilevels_components"))
+    end
+
+    it "doesn't allow a user selectable theme to be a child" do
+      parent = Fabricate(:theme)
+      selectable_theme = Fabricate(:theme, user_selectable: true)
+
+      child_theme = ChildTheme.new(parent_theme: parent, child_theme: selectable_theme)
+      expect(child_theme.valid?).to eq(false)
+      expect(child_theme.errors.full_messages).to contain_exactly(I18n.t("themes.errors.component_no_user_selectable"))
+    end
+
+    it "doesn't allow a default theme to be child" do
+      parent = Fabricate(:theme)
+      default = Fabricate(:theme)
+      default.set_default!
+
+      child_theme = ChildTheme.new(parent_theme: parent, child_theme: default)
+      expect(child_theme.valid?).to eq(false)
+      expect(child_theme.errors.full_messages).to contain_exactly(I18n.t("themes.errors.component_no_default"))
+    end
+  end
+end

spec/models/color_scheme_spec.rb

@@ -10,15 +10,15 @@ describe ColorScheme do
 
   it "correctly invalidates theme css when changed" do
     scheme = ColorScheme.create_from_base(name: 'Bob')
-    theme = Theme.new(name: 'Amazing Theme', color_scheme_id: scheme.id, user_id: -1)
+    theme = Fabricate(:theme, color_scheme_id: scheme.id)
     theme.set_field(name: :scss, target: :desktop, value: '.bob {color: $primary;}')
     theme.save!
 
-    href = Stylesheet::Manager.stylesheet_href(:desktop_theme, theme.id)
+    href = Stylesheet::Manager.stylesheet_data(:desktop_theme, theme.id)[0][:new_href]
 
     ColorSchemeRevisor.revise(scheme, colors: [{ name: 'primary', hex: 'bbb' }])
 
-    href2 = Stylesheet::Manager.stylesheet_href(:desktop_theme, theme.id)
+    href2 = Stylesheet::Manager.stylesheet_data(:desktop_theme, theme.id)[0][:new_href]
 
     expect(href).not_to eq(href2)
   end

spec/models/remote_theme_spec.rb

@@ -189,7 +189,7 @@ describe RemoteTheme do
 
   context ".out_of_date_themes" do
     let(:remote) { RemoteTheme.create!(remote_url: "https://github.com/org/testtheme") }
-    let!(:theme) { Theme.create!(remote_theme_id: remote.id, name: "Test Theme", user_id: -1) }
+    let!(:theme) { Fabricate(:theme, remote_theme: remote) }
 
     it "finds out of date themes" do
       remote.update!(local_version: "old version", remote_version: "new version", commits_behind: 2)

spec/models/site_spec.rb

@@ -17,9 +17,9 @@ describe Site do
   end
 
   it "includes user themes and expires them as needed" do
-    default_theme = Theme.create!(user_id: -1, name: 'default')
+    default_theme = Fabricate(:theme)
     SiteSetting.default_theme_id = default_theme.id
-    user_theme = Theme.create!(user_id: -1, name: 'user theme', user_selectable: true)
+    user_theme = Fabricate(:theme, user_selectable: true)
 
     anon_guardian = Guardian.new
     user_guardian = Guardian.new(Fabricate(:user))

spec/models/theme_field_spec.rb

@@ -7,6 +7,26 @@ describe ThemeField do
     ThemeField.destroy_all
   end
 
+  describe "scope: find_by_theme_ids" do
+    it "returns result in the specified order" do
+      theme = Fabricate(:theme)
+      theme2 = Fabricate(:theme)
+      theme3 = Fabricate(:theme)
+
+      (0..1).each do |num|
+        ThemeField.create!(theme: theme, target_id: num, name: "header", value: "<a>html</a>")
+        ThemeField.create!(theme: theme2, target_id: num, name: "header", value: "<a>html</a>")
+        ThemeField.create!(theme: theme3, target_id: num, name: "header", value: "<a>html</a>")
+      end
+
+      expect(ThemeField.find_by_theme_ids(
+        [theme3.id, theme.id, theme2.id]
+      ).pluck(:theme_id)).to eq(
+        [theme3.id, theme3.id, theme.id, theme.id, theme2.id, theme2.id]
+      )
+    end
+  end
+
   it "correctly generates errors for transpiled js" do
     html = <<HTML
 <script type="text/discourse-plugin" version="0.8">

spec/models/theme_spec.rb

@@ -19,15 +19,16 @@ describe Theme do
   end
 
   let :customization do
-    Theme.create!(customization_params)
+    Fabricate(:theme, customization_params)
   end
 
+  let(:theme) { Fabricate(:theme, user: user) }
+  let(:child) { Fabricate(:theme, user: user) }
   it 'can properly clean up color schemes' do
-    theme = Theme.create!(name: 'bob', user_id: -1)
     scheme = ColorScheme.create!(theme_id: theme.id, name: 'test')
     scheme2 = ColorScheme.create!(theme_id: theme.id, name: 'test2')
 
-    Theme.create!(name: 'bob', user_id: -1, color_scheme_id: scheme2.id)
+    Fabricate(:theme, color_scheme_id: scheme2.id)
 
     theme.destroy!
     scheme2.reload
@@ -38,8 +39,6 @@ describe Theme do
   end
 
   it 'can support child themes' do
-    child = Theme.new(name: '2', user_id: user.id)
-
     child.set_field(target: :common, name: "header", value: "World")
     child.set_field(target: :desktop, name: "header", value: "Desktop")
     child.set_field(target: :mobile, name: "header", value: "Mobile")
@@ -54,7 +53,7 @@ describe Theme do
 
     expect(Theme.lookup_field(child.id, :mobile, :header)).to eq("Worldie\nMobile")
 
-    parent = Theme.new(name: '1', user_id: user.id)
+    parent = Fabricate(:theme, user: user)
 
     parent.set_field(target: :common, name: "header", value: "Common Parent")
     parent.set_field(target: :mobile, name: "header", value: "Mobile Parent")
@@ -68,18 +67,39 @@ describe Theme do
   end
 
   it 'can correctly find parent themes' do
-    grandchild = Theme.create!(name: 'grandchild', user_id: user.id)
+    theme.add_child_theme!(child)
-    child = Theme.create!(name: 'child', user_id: user.id)
+
-    theme = Theme.create!(name: 'theme', user_id: user.id)
+    expect(child.dependant_themes.length).to eq(1)
+  end
+
+  it "doesn't allow multi-level theme components" do
+    grandchild = Fabricate(:theme, user: user)
+    grandparent = Fabricate(:theme, user: user)
 
     theme.add_child_theme!(child)
-    child.add_child_theme!(grandchild)
+    expect do
+      child.add_child_theme!(grandchild)
+    end.to raise_error(Discourse::InvalidParameters, I18n.t("themes.errors.no_multilevels_components"))
 
-    expect(grandchild.dependant_themes.length).to eq(2)
+    expect do
+      grandparent.add_child_theme!(theme)
+    end.to raise_error(Discourse::InvalidParameters, I18n.t("themes.errors.no_multilevels_components"))
+  end
+
+  it "doesn't allow a child to be user selectable" do
+    theme.add_child_theme!(child)
+    child.update(user_selectable: true)
+    expect(child.errors.full_messages).to contain_exactly(I18n.t("themes.errors.component_no_user_selectable"))
+  end
+
+  it "doesn't allow a child to be set as the default theme" do
+    theme.add_child_theme!(child)
+    expect do
+      child.set_default!
+    end.to raise_error(Discourse::InvalidParameters, I18n.t("themes.errors.component_no_default"))
   end
 
   it 'should correct bad html in body_tag_baked and head_tag_baked' do
-    theme = Theme.new(user_id: -1, name: "test")
     theme.set_field(target: :common, name: "head_tag", value: "<b>I am bold")
     theme.save!
 
@@ -95,7 +115,6 @@ describe Theme do
       {{hello}}
     </script>
 HTML
-    theme = Theme.new(user_id: -1, name: "test")
     theme.set_field(target: :common, name: "header", value: with_template)
     theme.save!
 
@@ -106,8 +125,6 @@ HTML
   end
 
   it 'should create body_tag_baked on demand if needed' do
-
-    theme = Theme.new(user_id: -1, name: "test")
     theme.set_field(target: :common, name: :body_tag, value: "<b>test")
     theme.save
 
@@ -116,6 +133,41 @@ HTML
     expect(Theme.lookup_field(theme.id, :desktop, :body_tag)).to match(/<b>test<\/b>/)
   end
 
+  it 'can find fields for multiple themes' do
+    theme2 = Fabricate(:theme)
+
+    theme.set_field(target: :common, name: :body_tag, value: "<b>testtheme1</b>")
+    theme2.set_field(target: :common, name: :body_tag, value: "<b>theme2test</b>")
+    theme.save!
+    theme2.save!
+
+    field = Theme.lookup_field([theme.id, theme2.id], :desktop, :body_tag)
+    expect(field).to match(/<b>testtheme1<\/b>/)
+    expect(field).to match(/<b>theme2test<\/b>/)
+  end
+
+  describe ".transform_ids" do
+    it "adds the child themes of the parent" do
+      child = Fabricate(:theme, id: 97)
+      child2 = Fabricate(:theme, id: 96)
+
+      theme.add_child_theme!(child)
+      theme.add_child_theme!(child2)
+      expect(Theme.transform_ids([theme.id])).to eq([theme.id, child2.id, child.id])
+      expect(Theme.transform_ids([theme.id, 94, 90])).to eq([theme.id, 90, 94, child2.id, child.id])
+    end
+
+    it "doesn't insert children when extend is false" do
+      child = Fabricate(:theme, id: 97)
+      child2 = Fabricate(:theme, id: 96)
+
+      theme.add_child_theme!(child)
+      theme.add_child_theme!(child2)
+      expect(Theme.transform_ids([theme.id], extend: false)).to eq([theme.id])
+      expect(Theme.transform_ids([theme.id, 94, 90, 70, 70], extend: false)).to eq([theme.id, 70, 90, 94])
+    end
+  end
+
   context "plugin api" do
     def transpile(html)
       f = ThemeField.create!(target_id: Theme.targets[:mobile], theme_id: 1, name: "after_header", value: html)
@@ -152,14 +204,12 @@ HTML
   context 'theme vars' do
 
     it 'works in parent theme' do
-
-      theme = Theme.new(name: 'theme', user_id: -1)
       theme.set_field(target: :common, name: :scss, value: 'body {color: $magic; }')
       theme.set_field(target: :common, name: :magic, value: 'red', type: :theme_var)
       theme.set_field(target: :common, name: :not_red, value: 'red', type: :theme_var)
       theme.save
 
-      parent_theme = Theme.new(name: 'parent theme', user_id: -1)
+      parent_theme = Fabricate(:theme)
       parent_theme.set_field(target: :common, name: :scss, value: 'body {background-color: $not_red; }')
       parent_theme.set_field(target: :common, name: :not_red, value: 'blue', type: :theme_var)
       parent_theme.save
@@ -171,7 +221,6 @@ HTML
     end
 
     it 'can generate scss based off theme vars' do
-      theme = Theme.new(name: 'theme', user_id: -1)
       theme.set_field(target: :common, name: :scss, value: 'body {color: $magic; content: quote($content)}')
       theme.set_field(target: :common, name: :magic, value: 'red', type: :theme_var)
       theme.set_field(target: :common, name: :content, value: 'Sam\'s Test', type: :theme_var)
@@ -187,7 +236,6 @@ HTML
     end
 
     it 'can handle uploads based of ThemeField' do
-      theme = Theme.new(name: 'theme', user_id: -1)
       upload = UploadCreator.new(image, "logo.png").create_for(-1)
       theme.set_field(target: :common, name: :logo, upload_id: upload.id, type: :theme_upload_var)
       theme.set_field(target: :common, name: :scss, value: 'body {background-image: url($logo)}')
@@ -210,7 +258,6 @@ HTML
 
   context "theme settings" do
     it "allows values to be used in scss" do
-      theme = Theme.new(name: "awesome theme", user_id: -1)
       theme.set_field(target: :settings, name: :yaml, value: "background_color: red\nfont_size: 25px")
       theme.set_field(target: :common, name: :scss, value: 'body {background-color: $background_color; font-size: $font-size}')
       theme.save!
@@ -227,7 +274,6 @@ HTML
     end
 
     it "allows values to be used in JS" do
-      theme = Theme.new(name: "awesome theme", user_id: -1)
       theme.set_field(target: :settings, name: :yaml, value: "name: bob")
       theme.set_field(target: :common, name: :after_header, value: '<script type="text/discourse-plugin" version="1.0">alert(settings.name); let a = ()=>{};</script>')
       theme.save!
@@ -263,26 +309,30 @@ HTML
   it 'correctly caches theme ids' do
     Theme.destroy_all
 
-    theme = Theme.create!(name: "bob", user_id: -1)
+    theme
+    theme2 = Fabricate(:theme)
 
-    expect(Theme.theme_ids).to eq(Set.new([theme.id]))
+    expect(Theme.theme_ids).to contain_exactly(theme.id, theme2.id)
-    expect(Theme.user_theme_ids).to eq(Set.new([]))
+    expect(Theme.user_theme_ids).to eq([])
 
-    theme.user_selectable = true
+    theme.update!(user_selectable: true)
-    theme.save
 
-    expect(Theme.user_theme_ids).to eq(Set.new([theme.id]))
+    expect(Theme.user_theme_ids).to contain_exactly(theme.id)
 
-    theme.user_selectable = false
+    theme2.update!(user_selectable: true)
-    theme.save
+    expect(Theme.user_theme_ids).to contain_exactly(theme.id, theme2.id)
+
+    theme.update!(user_selectable: false)
+    theme2.update!(user_selectable: false)
 
     theme.set_default!
-    expect(Theme.user_theme_ids).to eq(Set.new([theme.id]))
+    expect(Theme.user_theme_ids).to contain_exactly(theme.id)
 
     theme.destroy
+    theme2.destroy
 
-    expect(Theme.theme_ids).to eq(Set.new([]))
+    expect(Theme.theme_ids).to eq([])
-    expect(Theme.user_theme_ids).to eq(Set.new([]))
+    expect(Theme.user_theme_ids).to eq([])
   end
 
   it 'correctly caches user_themes template' do
@@ -292,8 +342,7 @@ HTML
     user_themes = JSON.parse(json)["user_themes"]
     expect(user_themes).to eq([])
 
-    theme = Theme.create!(name: "bob", user_id: -1, user_selectable: true)
+    theme = Fabricate(:theme, name: "bob", user_selectable: true)
-    theme.save!
 
     json = Site.json_for(guardian)
     user_themes = JSON.parse(json)["user_themes"].map { |t| t["name"] }
@@ -320,7 +369,6 @@ HTML
   it 'handles settings cache correctly' do
     Theme.destroy_all
 
-    theme = Theme.create!(name: "awesome theme", user_id: -1)
     expect(cached_settings(theme.id)).to eq("{}")
 
     theme.set_field(target: :settings, name: "yaml", value: "boolean_setting: true")
@@ -330,7 +378,6 @@ HTML
     theme.settings.first.value = "false"
     expect(cached_settings(theme.id)).to match(/\"boolean_setting\":false/)
 
-    child = Theme.create!(name: "child theme", user_id: -1)
     child.set_field(target: :settings, name: "yaml", value: "integer_setting: 54")
 
     child.save!
@@ -347,5 +394,4 @@ HTML
     expect(json).not_to match(/\"integer_setting\":54/)
     expect(json).to match(/\"boolean_setting\":false/)
   end
-
 end

spec/requests/admin/staff_action_logs_controller_spec.rb

@@ -30,7 +30,7 @@ describe Admin::StaffActionLogsController do
 
   describe '#diff' do
     it 'can generate diffs for theme changes' do
-      theme = Theme.new(user_id: -1, name: 'bob')
+      theme = Fabricate(:theme)
       theme.set_field(target: :mobile, name: :scss, value: 'body {.up}')
       theme.set_field(target: :common, name: :scss, value: 'omit-dupe')
 

spec/requests/admin/themes_controller_spec.rb

@@ -49,7 +49,7 @@ describe Admin::ThemesController do
 
     it 'can import a theme with an upload' do
       upload = Fabricate(:upload)
-      theme = Theme.new(name: 'with-upload', user_id: -1)
+      theme = Fabricate(:theme)
       upload = UploadCreator.new(image, "logo.png").create_for(-1)
       theme.set_field(target: :common, name: :logo, upload_id: upload.id, type: :theme_upload_var)
       theme.save!
@@ -93,7 +93,7 @@ describe Admin::ThemesController do
       ColorScheme.destroy_all
       Theme.destroy_all
 
-      theme = Theme.new(name: 'my name', user_id: -1)
+      theme = Fabricate(:theme)
       theme.set_field(target: :common, name: :scss, value: '.body{color: black;}')
       theme.set_field(target: :desktop, name: :after_header, value: '<b>test</b>')
 
@@ -141,7 +141,7 @@ describe Admin::ThemesController do
   end
 
   describe '#update' do
-    let(:theme) { Theme.create(name: 'my name', user_id: -1) }
+    let(:theme) { Fabricate(:theme) }
 
     it 'can change default theme' do
       SiteSetting.default_theme_id = -1
@@ -169,7 +169,7 @@ describe Admin::ThemesController do
       theme.set_field(target: :common, name: :scss, value: '.body{color: black;}')
       theme.save
 
-      child_theme = Theme.create(name: 'my name', user_id: -1)
+      child_theme = Fabricate(:theme)
 
       upload = Fabricate(:upload)
 
@@ -198,5 +198,17 @@ describe Admin::ThemesController do
       expect(json["theme"]["child_themes"].length).to eq(1)
       expect(UserHistory.where(action: UserHistory.actions[:change_theme]).count).to eq(1)
     end
+
+    it 'returns the right error message' do
+      parent = Fabricate(:theme)
+      parent.add_child_theme!(theme)
+
+      put "/admin/themes/#{theme.id}.json", params: {
+        theme: { default: true }
+      }
+
+      expect(response.status).to eq(400)
+      expect(JSON.parse(response.body)["errors"].first).to include(I18n.t("themes.errors.component_no_default"))
+    end
   end
 end

spec/requests/application_controller_spec.rb

@@ -33,4 +33,74 @@ RSpec.describe ApplicationController do
     end
   end
 
+  describe "#handle_theme" do
+    let(:theme) { Fabricate(:theme, user_selectable: true) }
+    let(:theme2) { Fabricate(:theme, user_selectable: true) }
+    let(:user) { Fabricate(:user) }
+    let(:admin) { Fabricate(:admin) }
+
+    before do
+      sign_in(user)
+    end
+
+    it "selects the theme the user has selected" do
+      user.user_option.update_columns(theme_ids: [theme.id])
+
+      get "/"
+      expect(response.status).to eq(200)
+      expect(controller.theme_ids).to eq([theme.id])
+
+      theme.update_attribute(:user_selectable, false)
+
+      get "/"
+      expect(response.status).to eq(200)
+      expect(controller.theme_ids).to eq([SiteSetting.default_theme_id])
+    end
+
+    it "can be overridden with a cookie" do
+      user.user_option.update_columns(theme_ids: [theme.id])
+
+      cookies['theme_ids'] = "#{theme2.id}|#{user.user_option.theme_key_seq}"
+
+      get "/"
+      expect(response.status).to eq(200)
+      expect(controller.theme_ids).to eq([theme2.id])
+
+      theme2.update!(user_selectable: false)
+      theme.add_child_theme!(theme2)
+      cookies['theme_ids'] = "#{theme.id},#{theme2.id}|#{user.user_option.theme_key_seq}"
+
+      get "/"
+      expect(response.status).to eq(200)
+      expect(controller.theme_ids).to eq([theme.id, theme2.id])
+    end
+
+    it "falls back to the default theme when the user has no cookies or preferences" do
+      user.user_option.update_columns(theme_ids: [])
+      cookies["theme_ids"] = nil
+      theme2.set_default!
+
+      get "/"
+      expect(response.status).to eq(200)
+      expect(controller.theme_ids).to eq([theme2.id])
+    end
+
+    it "can be overridden with preview_theme_id param" do
+      sign_in(admin)
+      cookies['theme_ids'] = "#{theme.id},#{theme2.id}|#{admin.user_option.theme_key_seq}"
+
+      get "/", params: { preview_theme_id: theme2.id }
+      expect(response.status).to eq(200)
+      expect(controller.theme_ids).to eq([theme2.id])
+    end
+
+    it "cookie can fail back to user if out of sync" do
+      user.user_option.update_columns(theme_ids: [theme.id])
+      cookies['theme_ids'] = "#{theme2.id}|#{user.user_option.theme_key_seq - 1}"
+
+      get "/"
+      expect(response.status).to eq(200)
+      expect(controller.theme_ids).to eq([theme.id])
+    end
+  end
 end

spec/requests/embed_controller_spec.rb

@@ -83,7 +83,7 @@ describe EmbedController do
     end
 
     it "includes CSS from embedded_scss field" do
-      theme = Theme.create!(name: "Awesome blog", user_id: -1)
+      theme = Fabricate(:theme)
       theme.set_default!
 
       ThemeField.create!(

spec/requests/stylesheets_controller_spec.rb

@@ -27,7 +27,7 @@ describe StylesheetsController do
 
   it 'can lookup theme specific css' do
     scheme = ColorScheme.create_from_base(name: "testing", colors: [])
-    theme = Theme.create!(name: "test", color_scheme_id: scheme.id, user_id: -1)
+    theme = Fabricate(:theme, color_scheme_id: scheme.id)
 
     builder = Stylesheet::Manager.new(:desktop, theme.id)
     builder.compile

spec/requests/topics_controller_spec.rb

@@ -1218,48 +1218,6 @@ RSpec.describe TopicsController do
       expect(response.headers['X-Robots-Tag']).to eq(nil)
     end
 
-    describe "themes" do
-      let(:theme) { Theme.create!(user_id: -1, name: 'bob', user_selectable: true) }
-      let(:theme2) { Theme.create!(user_id: -1, name: 'bobbob', user_selectable: true) }
-
-      before do
-        sign_in(user)
-      end
-
-      it "selects the theme the user has selected" do
-        user.user_option.update_columns(theme_ids: [theme.id])
-
-        get "/t/#{topic.id}"
-        expect(response).to be_redirect
-        expect(controller.theme_id).to eq(theme.id)
-
-        theme.update_attribute(:user_selectable, false)
-
-        get "/t/#{topic.id}"
-        expect(response).to be_redirect
-        expect(controller.theme_id).not_to eq(theme.id)
-      end
-
-      it "can be overridden with a cookie" do
-        user.user_option.update_columns(theme_ids: [theme.id])
-
-        cookies['theme_ids'] = "#{theme2.id}|#{user.user_option.theme_key_seq}"
-
-        get "/t/#{topic.id}"
-        expect(response).to be_redirect
-        expect(controller.theme_id).to eq(theme2.id)
-      end
-
-      it "cookie can fail back to user if out of sync" do
-        user.user_option.update_columns(theme_ids: [theme.id])
-        cookies['theme_ids'] = "#{theme2.id}|#{user.user_option.theme_key_seq - 1}"
-
-        get "/t/#{topic.id}"
-        expect(response).to be_redirect
-        expect(controller.theme_id).to eq(theme.id)
-      end
-    end
-
     it "doesn't store an incoming link when there's no referer" do
       expect {
         get "/t/#{topic.id}.json"

spec/requests/users_controller_spec.rb

@@ -1440,7 +1440,7 @@ describe UsersController do
             notification_level: TagUser.notification_levels[:watching]
           ).pluck(:tag_id)).to contain_exactly(tags[0].id, tags[1].id)
 
-          theme = Theme.create(name: "test", user_selectable: true, user_id: -1)
+          theme = Fabricate(:theme, user_selectable: true)
 
           put "/u/#{user.username}.json", params: {
             muted_usernames: "",

spec/services/staff_action_logger_spec.rb

@@ -154,7 +154,7 @@ describe StaffActionLogger do
     end
 
     let :theme do
-      Theme.new(name: 'bob', user_id: -1)
+      Fabricate(:theme)
     end
 
     it "logs new site customizations" do
@@ -188,7 +188,7 @@ describe StaffActionLogger do
     end
 
     it "creates a new UserHistory record" do
-      theme = Theme.new(name: 'Banana')
+      theme = Fabricate(:theme)
       theme.set_field(target: :common, name: :scss, value: "body{margin: 10px;}")
 
       log_record = logger.log_theme_destroy(theme)

spec/services/user_merger_spec.rb

@@ -478,7 +478,7 @@ describe UserMerger do
   end
 
   it "updates themes" do
-    theme = Theme.create!(name: 'my name', user_id: source_user.id)
+    theme = Fabricate(:theme, user: source_user)
     merge_users!
 
     expect(theme.reload.user_id).to eq(target_user.id)

spec/services/user_updater_spec.rb

@@ -82,7 +82,7 @@ describe UserUpdater do
       updater = UserUpdater.new(acting_user, user)
       date_of_birth = Time.zone.now
 
-      theme = Theme.create!(user_id: -1, name: "test", user_selectable: true)
+      theme = Fabricate(:theme, user_selectable: true)
 
       seq = user.user_option.theme_key_seq