core(driver): don't clear indexedb, websql, or localstorage before run

lighthouse-core/audits/multi-check-audit.js

@@ -53,7 +53,7 @@ class MultiCheckAudit extends Audit {
     if (result.failures.length > 0) {
       return {
         score: 0,
-        // TODO(#7238): make this i18n-able.
+        // TODO(#11495): make this i18n-able.
         explanation: `Failures: ${result.failures.join(',\n')}.`,
         details,
       };

lighthouse-core/gather/driver.js

@@ -12,6 +12,7 @@ const LHElement = require('../lib/lh-element.js');
 const LHError = require('../lib/lh-error.js');
 const NetworkRequest = require('../lib/network-request.js');
 const EventEmitter = require('events').EventEmitter;
+const i18n = require('../lib/i18n/i18n.js');
 const URL = require('../lib/url-shim.js');
 const constants = require('../config/constants.js');
 
@@ -24,6 +25,24 @@ const pageFunctions = require('../lib/page-functions.js');
 // eslint-disable-next-line no-unused-vars
 const Connection = require('./connections/connection.js');
 
+const UIStrings = {
+  /**
+   * @description A warning that previously-saved data may have affected the measured performance and instructions on how to avoid the problem. "locations" will be a list of possible types of data storage locations, e.g. "IndexedDB",  "Local Storage", or "Web SQL".
+   * @example {IndexedDB, Local Storage} locations
+   */
+  warningData: `{locationCount, plural,
+    =1 {There may be stored data affecting loading performance in this location: {locations}. ` +
+      `Audit this page in an incognito window to prevent those resources ` +
+      `from affecting your scores.}
+    other {There may be stored data affecting loading ` +
+      `performance in these locations: {locations}. ` +
+      `Audit this page in an incognito window to prevent those resources ` +
+      `from affecting your scores.}
+  }`,
+};
+
+const str_ = i18n.createMessageInstanceIdFn(__filename, UIStrings);
+
 // Controls how long to wait after FCP before continuing
 const DEFAULT_PAUSE_AFTER_FCP = 0;
 // Controls how long to wait after onLoad before continuing
@@ -1445,16 +1464,15 @@ class Driver {
   async clearDataForOrigin(url) {
     const origin = new URL(url).origin;
 
-    // Clear all types of storage except cookies, so the user isn't logged out.
+    // Clear some types of storage.
+    // Cookies are not cleared, so the user isn't logged out.
+    // indexeddb, websql, and localstorage are not cleared to prevent loss of potentially important data.
     //   https://chromedevtools.github.io/debugger-protocol-viewer/tot/Storage/#type-StorageType
     const typesToClear = [
       'appcache',
       // 'cookies',
       'file_systems',
-      'indexeddb',
-      'local_storage',
       'shader_cache',
-      'websql',
       'service_workers',
       'cache_storage',
     ].join(',');
@@ -1477,6 +1495,33 @@ class Driver {
     }
   }
 
+  /**
+   * @param {string} url
+   * @return {Promise<LH.IcuMessage | undefined>}
+   */
+  async getImportantStorageWarning(url) {
+    const usageData = await this.sendCommand('Storage.getUsageAndQuota', {
+      origin: url,
+    });
+    /** @type {Record<string, string>} */
+    const storageTypeNames = {
+      local_storage: 'Local Storage',
+      indexeddb: 'IndexedDB',
+      websql: 'Web SQL',
+    };
+    const locations = usageData.usageBreakdown
+      .filter(usage => usage.usage)
+      .map(usage => storageTypeNames[usage.storageType] || '')
+      .filter(Boolean);
+    if (locations.length) {
+      // TODO(#11495): Use Intl.ListFormat with Node 12
+      return str_(
+        UIStrings.warningData,
+        {locations: locations.join(', '), locationCount: locations.length}
+      );
+    }
+  }
+
   /**
    * Cache native functions/objects inside window
    * so we are sure polyfills do not overwrite the native implementations
@@ -1549,3 +1594,4 @@ class Driver {
 }
 
 module.exports = Driver;
+module.exports.UIStrings = UIStrings;

lighthouse-core/gather/gather-runner.js

@@ -105,9 +105,10 @@ class GatherRunner {
   /**
    * @param {Driver} driver
    * @param {{requestedUrl: string, settings: LH.Config.Settings}} options
+   * @param {(string | LH.IcuMessage)[]} LighthouseRunWarnings
    * @return {Promise<void>}
    */
-  static async setupDriver(driver, options) {
+  static async setupDriver(driver, options, LighthouseRunWarnings) {
     const status = {msg: 'Initializing…', id: 'lh:gather:setupDriver'};
     log.time(status);
     const resetStorage = !options.settings.disableStorageReset;
@@ -119,7 +120,13 @@ class GatherRunner {
     await driver.registerPerformanceObserver();
     await driver.dismissJavaScriptDialogs();
     await driver.registerRequestIdleCallbackWrap(options.settings);
-    if (resetStorage) await driver.clearDataForOrigin(options.requestedUrl);
+    if (resetStorage) {
+      const warning = await driver.getImportantStorageWarning(options.requestedUrl);
+      if (warning) {
+        LighthouseRunWarnings.push(warning);
+      }
+      await driver.clearDataForOrigin(options.requestedUrl);
+    }
     log.timeEnd(status);
   }
 
@@ -654,7 +661,7 @@ class GatherRunner {
       const baseArtifacts = await GatherRunner.initializeBaseArtifacts(options);
       baseArtifacts.BenchmarkIndex = await options.driver.getBenchmarkIndex();
 
-      await GatherRunner.setupDriver(driver, options);
+      await GatherRunner.setupDriver(driver, options, baseArtifacts.LighthouseRunWarnings);
 
       let isFirstPass = true;
       for (const passConfig of passConfigs) {

lighthouse-core/test/gather/driver-test.js

@@ -913,6 +913,64 @@ describe('.goOnline', () => {
   });
 });
 
+describe('.clearDataForOrigin', () => {
+  it('only clears data from certain locations', async () => {
+    let foundStorageTypes;
+    connectionStub.sendCommand = createMockSendCommandFn()
+      .mockResponse('Storage.clearDataForOrigin', ({storageTypes}) => {
+        foundStorageTypes = storageTypes;
+      });
+    await driver.clearDataForOrigin('https://example.com');
+    // Should not see cookies, websql, indexeddb, or local_storage.
+    // Cookies are not cleared to preserve login.
+    // websql, indexeddb, and local_storage are not cleared to preserve important user data.
+    expect(foundStorageTypes).toMatchInlineSnapshot(
+      `"appcache,file_systems,shader_cache,service_workers,cache_storage"`
+    );
+  });
+});
+
+describe('.getImportantDataWarning', () => {
+  it('properly returns warning', async () => {
+    connectionStub.sendCommand = createMockSendCommandFn()
+      .mockResponse('Storage.getUsageAndQuota', {usageBreakdown: [
+        {storageType: 'local_storage', usage: 5},
+        {storageType: 'indexeddb', usage: 5},
+        {storageType: 'websql', usage: 0},
+        {storageType: 'appcache', usage: 5},
+        {storageType: 'cookies', usage: 5},
+        {storageType: 'file_systems', usage: 5},
+        {storageType: 'shader_cache', usage: 5},
+        {storageType: 'service_workers', usage: 5},
+        {storageType: 'cache_storage', usage: 0},
+      ]});
+    const warning = await driver.getImportantStorageWarning('https://example.com');
+    expect(warning).toBeDisplayString(
+      'There may be stored data affecting loading performance in ' +
+      'these locations: Local Storage, IndexedDB. ' +
+      'Audit this page in an incognito window to prevent those resources ' +
+      'from affecting your scores.'
+    );
+  });
+
+  it('only warn for certain locations', async () => {
+    connectionStub.sendCommand = createMockSendCommandFn()
+      .mockResponse('Storage.getUsageAndQuota', {usageBreakdown: [
+        {storageType: 'local_storage', usage: 0},
+        {storageType: 'indexeddb', usage: 0},
+        {storageType: 'websql', usage: 0},
+        {storageType: 'appcache', usage: 5},
+        {storageType: 'cookies', usage: 5},
+        {storageType: 'file_systems', usage: 5},
+        {storageType: 'shader_cache', usage: 5},
+        {storageType: 'service_workers', usage: 5},
+        {storageType: 'cache_storage', usage: 5},
+      ]});
+    const warning = await driver.getImportantStorageWarning('https://example.com');
+    expect(warning).toBeUndefined();
+  });
+});
+
 describe('Domain.enable/disable State', () => {
   it('dedupes (simple)', async () => {
     connectionStub.sendCommand = createMockSendCommandFn()

lighthouse-core/test/gather/fake-driver.js

@@ -62,6 +62,9 @@ function makeFakeDriver({protocolGetVersionResponse}) {
     },
     cleanBrowserCaches() {},
     clearDataForOrigin() {},
+    getImportantStorageWarning() {
+      return Promise.resolve(undefined);
+    },
     cacheNatives() {
       return Promise.resolve();
     },

lighthouse-core/test/gather/gather-runner-test.js

@@ -111,6 +111,9 @@ class EmulationDriver extends Driver {
   registerRequestIdleCallbackWrap() {
     return Promise.resolve();
   }
+  getImportantStorageWarning() {
+    return Promise.resolve(undefined);
+  }
 }
 
 const fakeDriver = require('./fake-driver.js');
@@ -415,6 +418,7 @@ describe('GatherRunner', function() {
       clearDataForOrigin: createCheck('calledClearStorage'),
       blockUrlPatterns: asyncFunc,
       setExtraHTTPHeaders: asyncFunc,
+      getImportantStorageWarning: asyncFunc,
     };
 
     return GatherRunner.setupDriver(driver, {settings: {}}).then(_ => {

types/jest.d.ts

@@ -20,6 +20,6 @@ declare namespace jest {
     /**
      * Asserts that an i18n string (using en-US) matches an expected pattern.
      */
-    toBeDisplayString: (pattern: RegExp) => R;
+    toBeDisplayString: (pattern: RegExp | string) => R;
   }
 }