Make DeviceList test pass

Includes making saveIfDirty() return a promise in case you care
about when changes got saved (which the test does).

spec/unit/crypto/DeviceList.spec.js

@@ -1,6 +1,7 @@
 import DeviceList from '../../../lib/crypto/DeviceList';
 import MockStorageApi from '../../MockStorageApi';
 import WebStorageSessionStore from '../../../lib/store/session/webstorage';
+import MemoryCryptoStore from '../../../lib/crypto/store/memory-crypto-store.js';
 import testUtils from '../../test-utils';
 import utils from '../../../lib/utils';
 
@@ -40,6 +41,7 @@ const signedDeviceList = {
 describe('DeviceList', function() {
     let downloadSpy;
     let sessionStore;
+    let cryptoStore;
 
     beforeEach(function() {
         testUtils.beforeEach(this); // eslint-disable-line no-invalid-this
@@ -47,6 +49,7 @@ describe('DeviceList', function() {
         downloadSpy = expect.createSpy();
         const mockStorage = new MockStorageApi();
         sessionStore = new WebStorageSessionStore(mockStorage);
+        cryptoStore = new MemoryCryptoStore(mockStorage);
     });
 
     function createTestDeviceList() {
@@ -56,7 +59,7 @@ describe('DeviceList', function() {
         const mockOlm = {
             verifySignature: function(key, message, signature) {},
         };
-        return new DeviceList(baseApis, sessionStore, mockOlm);
+        return new DeviceList(baseApis, cryptoStore, sessionStore, mockOlm);
     }
 
     it("should successfully download and store device keys", function() {
@@ -72,7 +75,7 @@ describe('DeviceList', function() {
         queryDefer1.resolve(utils.deepCopy(signedDeviceList));
 
         return prom1.then(() => {
-            const storedKeys = sessionStore.getEndToEndDevicesForUser('@test1:sw1v.org');
+            const storedKeys = dl.getRawStoredDevicesForUser('@test1:sw1v.org');
             expect(Object.keys(storedKeys)).toEqual(['HGKAWHRVJQ']);
         });
     });
@@ -97,14 +100,15 @@ describe('DeviceList', function() {
         dl.invalidateUserDeviceList('@test1:sw1v.org');
         dl.refreshOutdatedDeviceLists();
 
+        dl.saveIfDirty().then(() => {
             // the first request completes
             queryDefer1.resolve({
                 device_keys: {
                     '@test1:sw1v.org': {},
                 },
             });
-
-        return prom1.then(() => {
+            return prom1;
+        }).then(() => {
             // uh-oh; user restarts before second request completes. The new instance
             // should know we never got a complete device list.
             console.log("Creating new devicelist to simulate app reload");
@@ -121,7 +125,7 @@ describe('DeviceList', function() {
             // allow promise chain to complete
             return prom3;
         }).then(() => {
-            const storedKeys = sessionStore.getEndToEndDevicesForUser('@test1:sw1v.org');
+            const storedKeys = dl.getRawStoredDevicesForUser('@test1:sw1v.org');
             expect(Object.keys(storedKeys)).toEqual(['HGKAWHRVJQ']);
         });
     });

src/crypto/DeviceList.js

@@ -91,6 +91,8 @@ export default class DeviceList {
 
         // Timeout for a scheduled save
         this._saveTimer = null;
+        // Promise resolved when device data is saved
+        this._savePromise = null;
     }
 
     /**
@@ -141,14 +143,18 @@ export default class DeviceList {
     /**
      * Save the device tracking state to storage, if any changes are
      * pending other than updating the sync token
+     *
+     * @return {Promise<bool>} True is the data was saved, false if
+     *     it was not (eg. because no changes were pending)
      */
     async saveIfDirty() {
-        if (!this._dirty) return;
+        if (!this._dirty) return Promise.resolve(False);
 
         if (this._saveTimer === null) {
             this._saveTimer = setTimeout(() => {
+                console.log('Saving device tracking data...');
                 this._saveTimer = null;
-                this._cryptoStore.doTxn(
+                this._savePromise = this._cryptoStore.doTxn(
                     'readwrite', [IndexedDBCryptoStore.STORE_DEVICE_DATA], (txn) => {
                         this._cryptoStore.storeEndToEndDeviceData({
                             devices: this._devices,
@@ -158,8 +164,11 @@ export default class DeviceList {
                     },
                 ).then(() => {
                     this._dirty = false;
+                    return True;
                 });
             }, 500);
+        } else {
+            return this._savePromise;
         }
     }