feat: support skipping cache and storage clear

lighthouse-cli/bin.ts

@@ -65,6 +65,7 @@ const cliFlags = yargs
     'port'
   ], 'Configuration:')
   .describe({
+    'disable-cache-clearing': 'Disable clearing of cache and storage before the run',
     'disable-device-emulation': 'Disable Nexus 5X emulation',
     'disable-cpu-throttling': 'Disable CPU throttling',
     'disable-network-throttling': 'Disable network throttling',
@@ -92,6 +93,7 @@ Example: --output-path=./lighthouse-results.html`
 
   // boolean values
   .boolean([
+    'disable-cache-clearing',
     'disable-device-emulation',
     'disable-cpu-throttling',
     'disable-network-throttling',

lighthouse-core/gather/gather-runner.js

@@ -91,13 +91,14 @@ class GatherRunner {
 
   static setupDriver(driver, options) {
     log.log('status', 'Initializing…');
+    const clearCache = !(options.flags && options.flags.disableCacheClearing);
     // Enable emulation based on flags
     return driver.assertNoSameOriginServiceWorkerClients(options.url)
       .then(_ => driver.beginEmulation(options.flags))
       .then(_ => driver.enableRuntimeEvents())
       .then(_ => driver.cacheNatives())
-      .then(_ => driver.cleanAndDisableBrowserCaches())
-      .then(_ => driver.clearDataForOrigin(options.url))
+      .then(_ => clearCache && driver.cleanAndDisableBrowserCaches())
+      .then(_ => clearCache && driver.clearDataForOrigin(options.url))
       .then(_ => driver.blockUrlPatterns(options.flags.blockedUrlPatterns || []));
   }
 

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

@@ -225,6 +225,60 @@ describe('GatherRunner', function() {
     });
   });
 
+  it('clears the network cache and origin storage', () => {
+    const asyncFunc = () => Promise.resolve();
+    const tests = {
+      calledDisableNetworkCache: false,
+      calledClearStorage: false,
+    };
+    const createCheck = variable => () => {
+      tests[variable] = true;
+      return Promise.resolve();
+    };
+    const driver = {
+      assertNoSameOriginServiceWorkerClients: asyncFunc,
+      beginEmulation: asyncFunc,
+      enableRuntimeEvents: asyncFunc,
+      cacheNatives: asyncFunc,
+      cleanAndDisableBrowserCaches: createCheck('calledDisableNetworkCache'),
+      clearDataForOrigin: createCheck('calledClearStorage'),
+      blockUrlPatterns: asyncFunc,
+    };
+
+    return GatherRunner.setupDriver(driver, {flags: {}}).then(_ => {
+      assert.equal(tests.calledDisableNetworkCache, true);
+      assert.equal(tests.calledClearStorage, true);
+    });
+  });
+
+  it('does not clear the network cache and origin storage when flag is set', () => {
+    const asyncFunc = () => Promise.resolve();
+    const tests = {
+      calledDisableNetworkCache: false,
+      calledClearStorage: false,
+    };
+    const createCheck = variable => () => {
+      tests[variable] = true;
+      return Promise.resolve();
+    };
+    const driver = {
+      assertNoSameOriginServiceWorkerClients: asyncFunc,
+      beginEmulation: asyncFunc,
+      enableRuntimeEvents: asyncFunc,
+      cacheNatives: asyncFunc,
+      cleanAndDisableBrowserCaches: createCheck('calledDisableNetworkCache'),
+      clearDataForOrigin: createCheck('calledClearStorage'),
+      blockUrlPatterns: asyncFunc,
+    };
+
+    return GatherRunner.setupDriver(driver, {
+      flags: {disableCacheClearing: true}
+    }).then(_ => {
+      assert.equal(tests.calledDisableNetworkCache, false);
+      assert.equal(tests.calledClearStorage, false);
+    });
+  });
+
   it('tells the driver to block given URL patterns when blockedUrlPatterns is given', () => {
     const receivedUrlPatterns = [];
     const urlPatterns = ['http://*.evil.com', '.jpg', '.woff2'];