Prevent level order to be modified (#8821)

(cherry picked from commit b87c537885)

src/settings/SettingsStore.ts

@@ -80,7 +80,8 @@ export const LEVEL_ORDER = [
 function getLevelOrder(setting: ISetting): SettingLevel[] {
     // Settings which support only a single setting level are inherently ordered
     if (setting.supportedLevelsAreOrdered || setting.supportedLevels.length === 1) {
-        return setting.supportedLevels;
+        // return a copy to prevent callers from modifying the array
+        return [...setting.supportedLevels];
     }
     return LEVEL_ORDER;
 }
@@ -359,7 +360,7 @@ export default class SettingsStore {
         if (!levelOrder.includes(SettingLevel.DEFAULT)) levelOrder.push(SettingLevel.DEFAULT); // always include default
 
         const minIndex = levelOrder.indexOf(level);
-        if (minIndex === -1) throw new Error("Level " + level + " is not prioritized");
+        if (minIndex === -1) throw new Error(`Level "${level}" for setting "${settingName}" is not prioritized`);
 
         const handlers = SettingsStore.getHandlers(settingName);
 

test/settings/SettingsStore-test.ts

@@ -0,0 +1,61 @@
+/*
+Copyright 2022 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import BasePlatform from "../../src/BasePlatform";
+import { SettingLevel } from "../../src/settings/SettingLevel";
+import SettingsStore from "../../src/settings/SettingsStore";
+import { mockPlatformPeg } from "../test-utils";
+
+const TEST_DATA = [
+    {
+        name: "Electron.showTrayIcon",
+        level: SettingLevel.PLATFORM,
+        value: true,
+    },
+];
+
+describe("SettingsStore", () => {
+    let platformSettings: object;
+
+    beforeAll(() => {
+        jest.clearAllMocks();
+        platformSettings = {};
+        mockPlatformPeg({
+            isLevelSupported: jest.fn().mockReturnValue(true),
+            supportsSetting: jest.fn().mockReturnValue(true),
+            setSettingValue: jest.fn().mockImplementation((settingName: string, value: any) => {
+                platformSettings[settingName] = value;
+            }),
+            getSettingValue: jest.fn().mockImplementation((settingName: string) => {
+                return platformSettings[settingName];
+            }),
+        } as unknown as BasePlatform);
+
+        TEST_DATA.forEach(d => {
+            SettingsStore.setValue(d.name, null, d.level, d.value);
+        });
+    });
+
+    describe("getValueAt", () => {
+        TEST_DATA.forEach(d => {
+            it(`should return the value "${d.level}"."${d.name}"`, () => {
+                expect(SettingsStore.getValueAt(d.level, d.name)).toBe(d.value);
+                // regression test #22545
+                expect(SettingsStore.getValueAt(d.level, d.name)).toBe(d.value);
+            });
+        });
+    });
+});