core(predictive-perf): predict FCP

lighthouse-core/audits/predictive-perf.js

@@ -27,13 +27,74 @@ class PredictivePerf extends Audit {
     return {
       name: 'predictive-perf',
       description: 'Predicted Performance (beta)',
-      helpText: 'Predicted performance evaluates how your site will perform under ' +
-          'a 3G connection on a mobile device.',
+      helpText:
+        'Predicted performance evaluates how your site will perform under ' +
+        'a 3G connection on a mobile device.',
       scoringMode: Audit.SCORING_MODES.NUMERIC,
       requiredArtifacts: ['traces', 'devtoolsLogs'],
     };
   }
 
+  /**
+   * @param {!Node} dependencyGraph
+   * @param {function()=} condition
+   * @return {!Set<string>}
+   */
+  static getScriptUrls(dependencyGraph, condition) {
+    const scriptUrls = new Set();
+
+    dependencyGraph.traverse(node => {
+      if (node.type === Node.TYPES.CPU) return;
+      if (node.record._resourceType !== WebInspector.resourceTypes.Script) return;
+      if (condition && !condition(node)) return;
+      scriptUrls.add(node.record.url);
+    });
+
+    return scriptUrls;
+  }
+
+  /**
+   * @param {!Node} dependencyGraph
+   * @param {!TraceOfTabArtifact} traceOfTab
+   * @return {!Node}
+   */
+  static getOptimisticFCPGraph(dependencyGraph, traceOfTab) {
+    const fcp = traceOfTab.timestamps.firstContentfulPaint;
+    const blockingScriptUrls = PredictivePerf.getScriptUrls(dependencyGraph, node => {
+      return (
+        node.endTime <= fcp && node.hasRenderBlockingPriority() && node.initiatorType !== 'script'
+      );
+    });
+
+    return dependencyGraph.cloneWithRelationships(node => {
+      if (node.endTime > fcp) return false;
+      // Include EvaluateScript tasks for blocking scripts
+      if (node.type === Node.TYPES.CPU) return node.isEvaluateScriptFor(blockingScriptUrls);
+      // Include non-script-initiated network requests with a render-blocking priority
+      return node.hasRenderBlockingPriority() && node.initiatorType !== 'script';
+    });
+  }
+
+  /**
+   * @param {!Node} dependencyGraph
+   * @param {!TraceOfTabArtifact} traceOfTab
+   * @return {!Node}
+   */
+  static getPessimisticFCPGraph(dependencyGraph, traceOfTab) {
+    const fcp = traceOfTab.timestamps.firstContentfulPaint;
+    const blockingScriptUrls = PredictivePerf.getScriptUrls(dependencyGraph, node => {
+      return node.endTime <= fcp && node.hasRenderBlockingPriority();
+    });
+
+    return dependencyGraph.cloneWithRelationships(node => {
+      if (node.endTime > fcp) return false;
+      // Include EvaluateScript tasks for blocking scripts
+      if (node.type === Node.TYPES.CPU) return node.isEvaluateScriptFor(blockingScriptUrls);
+      // Include all network requests that had render-blocking priority (even script-initiated)
+      return node.hasRenderBlockingPriority();
+    });
+  }
+
   /**
    * @param {!Node} dependencyGraph
    * @param {!TraceOfTabArtifact} traceOfTab
@@ -116,6 +177,8 @@ class PredictivePerf extends Audit {
       artifacts.requestTraceOfTab(trace),
     ]).then(([graph, traceOfTab]) => {
       const graphs = {
+        optimisticFCP: PredictivePerf.getOptimisticFCPGraph(graph, traceOfTab),
+        pessimisticFCP: PredictivePerf.getPessimisticFCPGraph(graph, traceOfTab),
         optimisticFMP: PredictivePerf.getOptimisticFMPGraph(graph, traceOfTab),
         pessimisticFMP: PredictivePerf.getPessimisticFMPGraph(graph, traceOfTab),
         optimisticTTCI: PredictivePerf.getOptimisticTTCIGraph(graph, traceOfTab),
@@ -129,6 +192,8 @@ class PredictivePerf extends Audit {
         const lastLongTaskEnd = PredictivePerf.getLastLongTaskEndTime(estimate.nodeTiming);
 
         switch (key) {
+          case 'optimisticFCP':
+          case 'pessimisticFCP':
           case 'optimisticFMP':
           case 'pessimisticFMP':
             values[key] = estimate.timeInMs;

lighthouse-core/gather/computed/page-dependency-graph.js

@@ -121,6 +121,15 @@ class PageDependencyGraphArtifact extends ComputedArtifact {
       } else if (node !== rootNode) {
         rootNode.addDependent(node);
       }
+
+      const redirects = Array.from(node.record.redirects || []);
+      redirects.push(node.record);
+
+      for (let i = 1; i < redirects.length; i++) {
+        const redirectNode = networkNodeOutput.idToNodeMap.get(redirects[i - 1].requestId);
+        const actualNode = networkNodeOutput.idToNodeMap.get(redirects[i].requestId);
+        actualNode.addDependency(redirectNode);
+      }
     });
   }
 

lighthouse-core/lib/dependency-graph/cpu-node.js

@@ -56,12 +56,26 @@ class CPUNode extends Node {
   }
 
   /**
+   * Returns true if this node contains a Layout task.
    * @return {boolean}
    */
   didPerformLayout() {
     return this._childEvents.some(evt => evt.name === 'Layout');
   }
 
+  /**
+   * Returns true if this node contains the EvaluateScript task for a URL in the given set.
+   * @param {!Set<string>} urls
+   * @return {boolean}
+   */
+  isEvaluateScriptFor(urls) {
+    return this._childEvents.some(evt => {
+      return evt.name === 'EvaluateScript' &&
+        evt.args.data &&
+        urls.has(evt.args.data.url);
+    });
+  }
+
   /**
    * @return {!CPUNode}
    */

lighthouse-core/test/audits/predictive-perf-test.js

@@ -26,10 +26,12 @@ describe('Performance: predictive performance audit', () => {
 
     return PredictivePerf.audit(artifacts).then(output => {
       assert.equal(output.score, 99);
-      assert.equal(Math.round(output.rawValue), 1696);
-      assert.equal(output.displayValue, '1,700\xa0ms');
+      assert.equal(Math.round(output.rawValue), 1333);
+      assert.equal(output.displayValue, '1,330\xa0ms');
 
       const valueOf = name => Math.round(output.extendedInfo.value[name]);
+      assert.equal(valueOf('optimisticFCP'), 607);
+      assert.equal(valueOf('pessimisticFCP'), 607);
       assert.equal(valueOf('optimisticFMP'), 754);
       assert.equal(valueOf('pessimisticFMP'), 1191);
       assert.equal(valueOf('optimisticTTCI'), 2438);