Fixed custom theme settings disappearing when confirming leave-without-save

refs https://github.com/TryGhost/Team/issues/1149

- `customThemeSettings.rollback()` was not performing the correct job, changed to rollback attributes on each model rather than resetting everything to empty
- moved leave confirmation handling to the `settings.design.index` route so that it's always called when moving to the change-theme route, previously with the behaviour on the main `settings.design` route the willtransition/deactivate was not called when expected because that route is still active when on `settings.design.change-theme`

ghost/admin/app/routes/settings/design.js

@@ -1,17 +1,12 @@
 import AuthenticatedRoute from 'ghost-admin/routes/authenticated';
-import {action} from '@ember/object';
 import {inject as service} from '@ember/service';
 
 export default class SettingsDesignRoute extends AuthenticatedRoute {
-    @service customThemeSettings;
     @service feature;
     @service modals;
     @service settings;
     @service ui;
 
-    confirmModal = null;
-    hasConfirmed = false;
-
     beforeModel() {
         super.beforeModel(...arguments);
 
@@ -32,27 +27,8 @@ export default class SettingsDesignRoute extends AuthenticatedRoute {
         this.ui.contextualNavMenu = 'design';
     }
 
-    @action
-    willTransition(transition) {
-        if (this.hasConfirmed) {
-            return true;
-        }
-
-        // always abort when not confirmed because Ember's router doesn't automatically wait on promises
-        transition.abort();
-
-        this.confirmUnsavedChanges().then((shouldLeave) => {
-            if (shouldLeave) {
-                this.hasConfirmed = true;
-                return transition.retry();
-            }
-        });
-    }
-
     deactivate() {
         this.ui.contextualNavMenu = null;
-        this.confirmModal = null;
-        this.hasConfirmed = false;
     }
 
     buildRouteInfoMetadata() {
@@ -60,25 +36,3 @@ export default class SettingsDesignRoute extends AuthenticatedRoute {
             mainClasses: ['gh-main-fullwidth']
         };
     }
-
-    confirmUnsavedChanges() {
-        if (!this.settings.get('hasDirtyAttributes') && !this.customThemeSettings.isDirty) {
-            return Promise.resolve(true);
-        }
-
-        if (!this.confirmModal) {
-            this.confirmModal = this.modals.open('modals/confirm-unsaved-changes')
-                .then((discardChanges) => {
-                    if (discardChanges === true) {
-                        this.settings.rollbackAttributes();
-                        this.customThemeSettings.rollback();
-                    }
-                    return discardChanges;
-                }).finally(() => {
-                    this.confirmModal = null;
-                });
-        }
-
-        return this.confirmModal;
-    }
-}

ghost/admin/app/routes/settings/design/index.js

@@ -0,0 +1,55 @@
+import AuthenticatedRoute from 'ghost-admin/routes/authenticated';
+import {action} from '@ember/object';
+import {inject as service} from '@ember/service';
+
+export default class SettingsDesignRoute extends AuthenticatedRoute {
+    @service customThemeSettings;
+    @service modals;
+    @service settings;
+
+    confirmModal = null;
+    hasConfirmed = false;
+
+    @action
+    willTransition(transition) {
+        if (this.hasConfirmed) {
+            return true;
+        }
+
+        // always abort when not confirmed because Ember's router doesn't automatically wait on promises
+        transition.abort();
+
+        this.confirmUnsavedChanges().then((shouldLeave) => {
+            if (shouldLeave) {
+                this.hasConfirmed = true;
+                return transition.retry();
+            }
+        });
+    }
+
+    deactivate() {
+        this.confirmModal = null;
+        this.hasConfirmed = false;
+    }
+
+    confirmUnsavedChanges() {
+        if (!this.settings.get('hasDirtyAttributes') && !this.customThemeSettings.isDirty) {
+            return Promise.resolve(true);
+        }
+
+        if (!this.confirmModal) {
+            this.confirmModal = this.modals.open('modals/confirm-unsaved-changes')
+                .then((discardChanges) => {
+                    if (discardChanges === true) {
+                        this.settings.rollbackAttributes();
+                        this.customThemeSettings.rollback();
+                    }
+                    return discardChanges;
+                }).finally(() => {
+                    this.confirmModal = null;
+                });
+        }
+
+        return this.confirmModal;
+    }
+}

ghost/admin/app/services/custom-theme-settings.js

@@ -79,10 +79,7 @@ export default class CustomThemeSettingsServices extends Service {
     }
 
     rollback() {
-        run(() => this.store.unloadAll('custom-theme-setting'));
-
-        this.settings = [];
-        this.settingGroups = [];
+        this.settings.forEach(setting => setting.rollbackAttributes());
     }
 
     _buildSettingGroups(settings) {