MaxPotentialFID

core/computed/metrics/lantern-max-potential-fid.js

@@ -5,63 +5,21 @@
  */
 
 import {makeComputedArtifact} from '../computed-artifact.js';
-import {LanternMetric} from './lantern-metric.js';
-import {BaseNode} from '../../lib/lantern/base-node.js';
+import {MaxPotentialFID} from '../../lib/lantern/metrics/max-potential-fid.js';
+import {getComputationDataParams} from './lantern-metric.js';
 import {LanternFirstContentfulPaint} from './lantern-first-contentful-paint.js';
 
-/** @typedef {import('../../lib/lantern/base-node.js').Node<LH.Artifacts.NetworkRequest>} Node */
+/** @typedef {import('../../lib/lantern/metric.js').Extras} Extras */
 
-class LanternMaxPotentialFID extends LanternMetric {
+class LanternMaxPotentialFID extends MaxPotentialFID {
   /**
-   * @return {LH.Gatherer.Simulation.MetricCoefficients}
-   */
-  static get COEFFICIENTS() {
-    return {
-      intercept: 0,
-      optimistic: 0.5,
-      pessimistic: 0.5,
-    };
-  }
-
-  /**
-   * @param {Node} dependencyGraph
-   * @return {Node}
-   */
-  static getOptimisticGraph(dependencyGraph) {
-    return dependencyGraph;
-  }
-
-  /**
-   * @param {Node} dependencyGraph
-   * @return {Node}
-   */
-  static getPessimisticGraph(dependencyGraph) {
-    return dependencyGraph;
-  }
-
-  /**
-   * @param {LH.Gatherer.Simulation.Result} simulation
-   * @param {import('../../lib/lantern/metric.js').Extras} extras
-   * @return {LH.Gatherer.Simulation.Result}
+   * @param {LH.Artifacts.MetricComputationDataInput} data
+   * @param {LH.Artifacts.ComputedContext} context
+   * @param {Omit<Extras, 'optimistic'>=} extras
+   * @return {Promise<LH.Artifacts.LanternMetric>}
    */
-  static getEstimateFromSimulation(simulation, extras) {
-    if (!extras.fcpResult) throw new Error('missing fcpResult');
-
-    // Intentionally use the opposite FCP estimate, a more pessimistic FCP means that more tasks
-    // are excluded from the FID computation, so a higher FCP means lower FID for same work.
-    const fcpTimeInMs = extras.optimistic
-      ? extras.fcpResult.pessimisticEstimate.timeInMs
-      : extras.fcpResult.optimisticEstimate.timeInMs;
-
-    const timings = LanternMaxPotentialFID.getTimingsAfterFCP(
-      simulation.nodeTimings,
-      fcpTimeInMs
-    );
-
-    return {
-      timeInMs: Math.max(...timings.map(timing => timing.duration), 16),
-      nodeTimings: simulation.nodeTimings,
-    };
+  static async computeMetricWithGraphs(data, context, extras) {
+    return this.compute(await getComputationDataParams(data, context), extras);
   }
 
   /**
@@ -71,18 +29,7 @@ class LanternMaxPotentialFID extends LanternMetric {
    */
   static async compute_(data, context) {
     const fcpResult = await LanternFirstContentfulPaint.request(data, context);
-    return super.computeMetricWithGraphs(data, context, {fcpResult});
-  }
-
-  /**
-   * @param {LH.Gatherer.Simulation.Result['nodeTimings']} nodeTimings
-   * @param {number} fcpTimeInMs
-   * @return {Array<{duration: number}>}
-   */
-  static getTimingsAfterFCP(nodeTimings, fcpTimeInMs) {
-    return Array.from(nodeTimings.entries())
-      .filter(([node, timing]) => node.type === BaseNode.TYPES.CPU && timing.endTime > fcpTimeInMs)
-      .map(([_, timing]) => timing);
+    return this.computeMetricWithGraphs(data, context, {fcpResult});
   }
 }
 

core/lib/lantern/metrics/max-potential-fid.js

@@ -0,0 +1,92 @@
+/**
+ * @license
+ * Copyright 2024 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import * as Lantern from '../types/lantern.js';
+import {Metric} from '../metric.js';
+import {BaseNode} from '../base-node.js';
+
+/** @typedef {import('../base-node.js').Node} Node */
+
+class MaxPotentialFID extends Metric {
+  /**
+   * @return {LH.Gatherer.Simulation.MetricCoefficients}
+   */
+  static get COEFFICIENTS() {
+    return {
+      intercept: 0,
+      optimistic: 0.5,
+      pessimistic: 0.5,
+    };
+  }
+
+  /**
+   * @param {Node} dependencyGraph
+   * @return {Node}
+   */
+  static getOptimisticGraph(dependencyGraph) {
+    return dependencyGraph;
+  }
+
+  /**
+   * @param {Node} dependencyGraph
+   * @return {Node}
+   */
+  static getPessimisticGraph(dependencyGraph) {
+    return dependencyGraph;
+  }
+
+  /**
+   * @param {LH.Gatherer.Simulation.Result} simulation
+   * @param {import('../metric.js').Extras} extras
+   * @return {LH.Gatherer.Simulation.Result}
+   */
+  static getEstimateFromSimulation(simulation, extras) {
+    if (!extras.fcpResult) throw new Error('missing fcpResult');
+
+    // Intentionally use the opposite FCP estimate, a more pessimistic FCP means that more tasks
+    // are excluded from the FID computation, so a higher FCP means lower FID for same work.
+    const fcpTimeInMs = extras.optimistic
+      ? extras.fcpResult.pessimisticEstimate.timeInMs
+      : extras.fcpResult.optimisticEstimate.timeInMs;
+
+    const timings = MaxPotentialFID.getTimingsAfterFCP(
+      simulation.nodeTimings,
+      fcpTimeInMs
+    );
+
+    return {
+      timeInMs: Math.max(...timings.map(timing => timing.duration), 16),
+      nodeTimings: simulation.nodeTimings,
+    };
+  }
+
+  /**
+   * @param {Lantern.Simulation.MetricComputationDataInput} data
+   * @param {Omit<import('../metric.js').Extras, 'optimistic'>=} extras
+   * @return {Promise<LH.Artifacts.LanternMetric>}
+   */
+  static compute(data, extras) {
+    const fcpResult = extras?.fcpResult;
+    if (!fcpResult) {
+      throw new Error('FCP is required to calculate the Max Potential FID metric');
+    }
+
+    return super.compute(data, extras);
+  }
+
+  /**
+   * @param {LH.Gatherer.Simulation.Result['nodeTimings']} nodeTimings
+   * @param {number} fcpTimeInMs
+   * @return {Array<{duration: number}>}
+   */
+  static getTimingsAfterFCP(nodeTimings, fcpTimeInMs) {
+    return Array.from(nodeTimings.entries())
+      .filter(([node, timing]) => node.type === BaseNode.TYPES.CPU && timing.endTime > fcpTimeInMs)
+      .map(([_, timing]) => timing);
+  }
+}
+
+export {MaxPotentialFID};