DBW: add audit for Date.now() usage

lighthouse-core/audits/dobetterweb/no-datenow.js

@@ -0,0 +1,82 @@
+/**
+ * @license
+ * Copyright 2016 Google Inc. All rights reserved.
+ *
+ * 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.
+ */
+
+/**
+ * @fileoverview Audit a page to see if it's using Date.now() (instead of a
+ * newer API like performance.now()).
+ */
+
+'use strict';
+
+const url = require('url');
+const Audit = require('../audit');
+const Formatter = require('../../formatters/formatter');
+
+class NoDateNowAudit extends Audit {
+
+  /**
+   * @return {!AuditMeta}
+   */
+  static get meta() {
+    return {
+      category: 'JavaScript',
+      name: 'no-datenow',
+      description: 'Site does not use Date.now() in its own scripts',
+      helpText: 'Consider using <a href="https://developer.mozilla.org/en-US/docs/Web/API/Performance/now" target="_blank">performance.now()</a>, which as better precision than <code>Date.now()</code> and always increases at a constant rate, independent of the system clock.',
+      requiredArtifacts: ['URL', 'DateNowUse']
+    };
+  }
+
+  /**
+   * @param {!Artifacts} artifacts
+   * @return {!AuditResult}
+   */
+  static audit(artifacts) {
+    if (typeof artifacts.DateNowUse === 'undefined' ||
+        artifacts.DateNowUse === -1) {
+      return NoDateNowAudit.generateAuditResult({
+        rawValue: -1,
+        debugString: 'DateNowUse gatherer did not run'
+      });
+    }
+
+    const pageHost = url.parse(artifacts.URL.finalUrl).host;
+    // Filter out Date.now() usage if script was on another host or an error with
+    // the same url:line:col combo has already been seen.
+    const results = artifacts.DateNowUse.dateNowUses.reduce((prev, err) => {
+      const jsonStr = JSON.stringify(err);
+      if (url.parse(err.url).host === pageHost && prev.indexOf(jsonStr) === -1) {
+        prev.push(jsonStr);
+      }
+      return prev;
+    }, []).map(err => {
+      err = JSON.parse(err);
+      err.misc = `(line: ${err.line}, col: ${err.col})`;
+      return err;
+    });
+
+    return NoDateNowAudit.generateAuditResult({
+      rawValue: results.length === 0,
+      extendedInfo: {
+        formatter: Formatter.SUPPORTED_FORMATS.URLLIST,
+        value: results
+      }
+    });
+  }
+}
+
+module.exports = NoDateNowAudit;

lighthouse-core/config/dobetterweb.json

@@ -3,15 +3,17 @@
     "network": true,
     "loadPage": true,
     "gatherers": [
-      "../gather/gatherers/dobetterweb/appcache",
-      "../gather/gatherers/dobetterweb/websql",
       "../gather/gatherers/https",
-      "../gather/gatherers/url"
+      "../gather/gatherers/url",
+      "../gather/gatherers/dobetterweb/appcache",
+      "../gather/gatherers/dobetterweb/datenow",
+      "../gather/gatherers/dobetterweb/websql"
     ]
   }],
 
   "audits": [
     "../audits/dobetterweb/appcache-manifest",
+    "../audits/dobetterweb/no-datenow",
     "../audits/dobetterweb/no-websql",
     "../audits/dobetterweb/uses-http2",
     "../audits/is-on-https"
@@ -43,6 +45,13 @@
           "description": "Resources made by this application should be severed over HTTP/2 for improved performance."
         }
       }
+    }, {
+      "name": "Using modern JavaScript features",
+      "criteria": {
+        "no-datenow": {
+          "rawValue": false
+        }
+      }
     }]
   }]
 }

lighthouse-core/formatters/partials/url-list.html

@@ -5,7 +5,8 @@
   .http-resource__url {
     margin-right: 8px;
   }
-  .http-resource__protocol {
+  .http-resource__protocol,
+  .http-resource__misc {
     color: #999;
   }
 </style>
@@ -15,7 +16,13 @@
     <summary>URLs</summary>
     {{#each this}}
       <div class="http-resource">
-        <span class="http-resource__url">{{this.url}}</span><span class="http-resource__protocol">({{this.protocol}})</span>
+        <span class="http-resource__url">{{this.url}}</span>
+        {{#if this.protocol}}
+          <span class="http-resource__protocol">({{this.protocol}})</span>
+        {{/if}}
+        {{#if this.misc}}
+          <span class="http-resource__misc">{{this.misc}}</span>
+        {{/if}}
       </div>
     {{/each}}
   </details>

lighthouse-core/gather/gatherers/dobetterweb/datenow.js

@@ -0,0 +1,71 @@
+/**
+ * @license
+ * Copyright 2016 Google Inc. All rights reserved.
+ *
+ * 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.
+ */
+
+/**
+ * @fileoverview Tests whether the page is using Date.now().
+ */
+
+/* global window, __returnResults */
+
+'use strict';
+
+const Gatherer = require('../gatherer');
+
+function patchDateNow() {
+  window.__stackTraceErrors = [];
+  // Override Date.now() so we know when if it's called.
+  const origDateNow = Date.now;
+  const originalPrepareStackTrace = Error.prepareStackTrace;
+  Date.now = function() {
+    // See v8's Stack Trace API https://github.com/v8/v8/wiki/Stack-Trace-API#customizing-stack-traces
+    Error.prepareStackTrace = function(error, structStackTrace) {
+      const lastCallFrame = structStackTrace[structStackTrace.length - 1];
+      const file = lastCallFrame.getFileName();
+      const line = lastCallFrame.getLineNumber();
+      const col = lastCallFrame.getColumnNumber();
+      window.__stackTraceErrors.push({url: file, line, col});
+      return {url: file, line, col}; // return value populates e.stack.
+    };
+    Error.captureStackTrace(new Error('__called Date.now()__'));
+    // Remove custom formatter so future results use v8's formatter.
+    Error.prepareStackTrace = originalPrepareStackTrace;
+    return origDateNow();
+  };
+}
+
+function collectDateNowUsage() {
+  __returnResults(window.__stackTraceErrors);
+}
+
+class DateNowUse extends Gatherer {
+
+  beforePass(options) {
+    return options.driver.evaluateScriptOnLoad(`(${patchDateNow.toString()}())`);
+  }
+
+  afterPass(options) {
+    return options.driver.evaluateAsync(`(${collectDateNowUsage.toString()}())`)
+        .then(dateNowUses => {
+          this.artifact.dateNowUses = dateNowUses;
+        }, _ => {
+          this.artifact = -1;
+          return;
+        });
+  }
+}
+
+module.exports = DateNowUse;

lighthouse-core/test/audits/dobetterweb/no-datenow-test.js

@@ -0,0 +1,83 @@
+/**
+ * Copyright 2016 Google Inc. All rights reserved.
+ *
+ * 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.
+ */
+'use strict';
+
+const DateNowUseAudit = require('../../../audits/dobetterweb/no-datenow.js');
+const assert = require('assert');
+
+const URL = 'https://example.com';
+
+/* eslint-env mocha */
+
+describe('Page does not use Date.now()', () => {
+  it('fails when no input present', () => {
+    const auditResult = DateNowUseAudit.audit({});
+    assert.equal(auditResult.rawValue, -1);
+    assert.ok(auditResult.debugString);
+  });
+
+  it('passes when Date.now() is not used', () => {
+    const auditResult = DateNowUseAudit.audit({
+      DateNowUse: {dateNowUses: []},
+      URL: {finalUrl: URL},
+    });
+    assert.equal(auditResult.rawValue, true);
+    assert.equal(auditResult.extendedInfo.value.length, 0);
+  });
+
+  it('passes when Date.now() is used on a different origin', () => {
+    const auditResult = DateNowUseAudit.audit({
+      DateNowUse: {
+        dateNowUses: [
+          {url: 'http://different.com/two', line: 2, col: 2},
+          {url: 'http://example2.com/two', line: 2, col: 22}
+        ]
+      },
+      URL: {finalUrl: URL},
+    });
+    assert.equal(auditResult.rawValue, true);
+    assert.equal(auditResult.extendedInfo.value.length, 0);
+  });
+
+  it('fails when Date.now() is used on the origin', () => {
+    const auditResult = DateNowUseAudit.audit({
+      DateNowUse: {
+        dateNowUses: [
+          {url: 'http://example.com/one', line: 1, col: 1},
+          {url: 'http://example.com/two', line: 10, col: 1},
+          {url: 'http://example2.com/two', line: 2, col: 22}
+        ]
+      },
+      URL: {finalUrl: URL},
+    });
+    assert.equal(auditResult.rawValue, false);
+    assert.equal(auditResult.extendedInfo.value.length, 2);
+  });
+
+  it('same file:line:col usage is deduped', () => {
+    const auditResult = DateNowUseAudit.audit({
+      DateNowUse: {
+        dateNowUses: [
+          {url: 'http://example.com/dupe', line: 1, col: 1},
+          {url: 'http://example.com/dupe', line: 1, col: 1}
+        ]
+      },
+      URL: {finalUrl: URL},
+    });
+    assert.equal(auditResult.rawValue, false);
+    assert.equal(auditResult.extendedInfo.value.length, 1);
+  });
+});