Enable the rust-crypto labs button (#12114)

* `LabsUserSettingsTab-test.tsx`: use a real `SdkConfig`

... instead of mocking it out. Doing so allows us more flexibility, and gives a
more realistic test.

* Enable the rust-crypto labs button

* fix up a test

src/MatrixClientPeg.ts

@@ -52,6 +52,7 @@ import ErrorDialog from "./components/views/dialogs/ErrorDialog";
 import PlatformPeg from "./PlatformPeg";
 import { formatList } from "./utils/FormattingUtils";
 import SdkConfig from "./SdkConfig";
+import { Features } from "./settings/Settings";
 
 export interface IMatrixClientCreds {
     homeserverUrl: string;
@@ -301,7 +302,7 @@ class MatrixClientPegClass implements IMatrixClientPeg {
             throw new Error("createClient must be called first");
         }
 
-        const useRustCrypto = SettingsStore.getValue("feature_rust_crypto");
+        const useRustCrypto = SettingsStore.getValue(Features.RustCrypto);
 
         // we want to make sure that the same crypto implementation is used throughout the lifetime of a device,
         // so persist the setting at the device layer

src/i18n/strings/en_EN.json

@@ -1447,7 +1447,10 @@
         "report_to_moderators": "Report to moderators",
         "report_to_moderators_description": "In rooms that support moderation, the “Report” button will let you report abuse to room moderators.",
         "rust_crypto": "Rust cryptography implementation",
-        "rust_crypto_disabled_notice": "Can currently only be enabled via config.json",
+        "rust_crypto_in_config": "Rust cryptography cannot be disabled on this deployment of %(brand)s",
+        "rust_crypto_in_config_description": "Switching to the Rust cryptography requires a migration process that may take several minutes. It cannot be disabled; use with caution!",
+        "rust_crypto_optin_warning": "Switching to the Rust cryptography requires a migration process that may take several minutes. To disable you will need to log out and back in; use with caution!",
+        "rust_crypto_requires_logout": "Once enabled, Rust cryptography can only be disabled by logging out and in again",
         "sliding_sync": "Sliding Sync mode",
         "sliding_sync_checking": "Checking…",
         "sliding_sync_configuration": "Sliding Sync configuration",

src/settings/Settings.tsx

@@ -46,6 +46,7 @@ import RustCryptoSdkController from "./controllers/RustCryptoSdkController";
 import ServerSupportUnstableFeatureController from "./controllers/ServerSupportUnstableFeatureController";
 import { WatchManager } from "./WatchManager";
 import { CustomTheme } from "../theme";
+import SettingsStore from "./SettingsStore";
 
 export const defaultWatchManager = new WatchManager();
 
@@ -94,6 +95,7 @@ export enum Features {
     VoiceBroadcastForceSmallChunks = "feature_voice_broadcast_force_small_chunks",
     NotificationSettings2 = "feature_notification_settings2",
     OidcNativeFlow = "feature_oidc_native_flow",
+    RustCrypto = "feature_rust_crypto",
 }
 
 export const labGroupNames: Record<LabGroup, TranslationKey> = {
@@ -480,15 +482,22 @@ export const SETTINGS: { [setting: string]: ISetting } = {
         description: _td("labs|oidc_native_flow_description"),
         default: false,
     },
-    "feature_rust_crypto": {
-        // use the rust matrix-sdk-crypto-js for crypto.
+    [Features.RustCrypto]: {
+        // use the rust matrix-sdk-crypto-wasm for crypto.
         isFeature: true,
         labsGroup: LabGroup.Developer,
-        configDisablesSetting: true,
+        // unlike most features, `configDisablesSetting` is false here.
         supportedLevels: LEVELS_DEVICE_ONLY_SETTINGS_WITH_CONFIG,
         displayName: _td("labs|rust_crypto"),
-        description: _td("labs|under_active_development"),
-        // shouldWarn: true,
+        description: () => {
+            if (SettingsStore.getValueAt(SettingLevel.CONFIG, Features.RustCrypto)) {
+                // It's enabled in the config, so you can't get rid of it even by logging out.
+                return _t("labs|rust_crypto_in_config_description");
+            } else {
+                return _t("labs|rust_crypto_optin_warning");
+            }
+        },
+        shouldWarn: true,
         default: false,
         controller: new RustCryptoSdkController(),
     },

src/settings/controllers/RustCryptoSdkController.ts

@@ -15,12 +15,35 @@ limitations under the License.
 */
 
 import { _t } from "../../languageHandler";
+import SettingsStore from "../SettingsStore";
+import { SettingLevel } from "../SettingLevel";
+import PlatformPeg from "../../PlatformPeg";
 import SettingController from "./SettingController";
+import { Features } from "../Settings";
+import { MatrixClientPeg } from "../../MatrixClientPeg";
+import SdkConfig from "../../SdkConfig";
 
 export default class RustCryptoSdkController extends SettingController {
+    public onChange(level: SettingLevel, roomId: string | null, newValue: any): void {
+        // If the crypto stack has already been initialized, we'll need to reload the app to make it take effect.
+        if (MatrixClientPeg.get()?.getCrypto()) {
+            PlatformPeg.get()?.reload();
+        }
+    }
+
     public get settingDisabled(): boolean | string {
-        // Currently this can only be changed via config.json. In future, we'll allow the user to *enable* this setting
-        // via labs, which will migrate their existing device to the rust-sdk implementation.
-        return _t("labs|rust_crypto_disabled_notice");
+        if (!SettingsStore.getValueAt(SettingLevel.DEVICE, Features.RustCrypto)) {
+            // If rust crypto has not yet been enabled for this device, you can turn it on, IF YOU DARE
+            return false;
+        }
+
+        if (SettingsStore.getValueAt(SettingLevel.CONFIG, Features.RustCrypto)) {
+            // It's enabled in the config, so you can't get rid of it even by logging out.
+            return _t("labs|rust_crypto_in_config", { brand: SdkConfig.get().brand });
+        }
+
+        // The setting is enabled at the device level, but not mandated at the config level.
+        // You can only turn it off by logging out and in again.
+        return _t("labs|rust_crypto_requires_logout");
     }
 }