core(fr): preserve scroll position in gatherers

core/gather/gatherers/accessibility.js

@@ -15,6 +15,11 @@ import {pageFunctions} from '../../lib/page-functions.js';
  */
 /* c8 ignore start */
 async function runA11yChecks() {
+  const originalScrollPosition = {
+    x: window.scrollX,
+    y: window.scrollY,
+  };
+
   /** @type {import('axe-core/axe')} */
   // @ts-expect-error - axe defined by axeLibSource
   const axe = window.axe;
@@ -72,13 +77,17 @@ async function runA11yChecks() {
   // are relative to the top of the page
   document.documentElement.scrollTop = 0;
 
-  return {
+  const result = {
     violations: axeResults.violations.map(createAxeRuleResultArtifact),
     incomplete: axeResults.incomplete.map(createAxeRuleResultArtifact),
     notApplicable: axeResults.inapplicable.map(result => ({id: result.id})), // FYI: inapplicable => notApplicable!
     passes: axeResults.passes.map(result => ({id: result.id})),
     version: axeResults.testEngine.version,
   };
+
+  window.scrollTo(originalScrollPosition.x, originalScrollPosition.y);
+
+  return result;
 }
 
 /**

core/gather/gatherers/seo/tap-targets.js

@@ -195,6 +195,11 @@ function gatherTapTargets(tapTargetsSelector, className) {
   /** @type {LH.Artifacts.TapTarget[]} */
   const targets = [];
 
+  const originalScrollPosition = {
+    x: window.scrollX,
+    y: window.scrollY,
+  };
+
   // Capture element positions relative to the top of the page
   window.scrollTo(0, 0);
 
@@ -279,6 +284,8 @@ function gatherTapTargets(tapTargetsSelector, className) {
 
   reenableFixedAndStickyElementPointerEvents();
 
+  window.scrollTo(originalScrollPosition.x, originalScrollPosition.y);
+
   return targets;
 }
 /* c8 ignore stop */

core/legacy/gather/driver.js

@@ -405,23 +405,6 @@ class Driver {
     return fetchResponseBodyFromCache(this.defaultSession, requestId, timeout);
   }
 
-  /**
-   * @param {{x: number, y: number}} position
-   * @return {Promise<void>}
-   */
-  scrollTo(position) {
-    const scrollExpression = `window.scrollTo(${position.x}, ${position.y})`;
-    return this.executionContext.evaluateAsync(scrollExpression, {useIsolation: true});
-  }
-
-  /**
-   * @return {Promise<{x: number, y: number}>}
-   */
-  getScrollPosition() {
-    return this.executionContext.evaluateAsync(`({x: window.scrollX, y: window.scrollY})`,
-      {useIsolation: true});
-  }
-
   /**
    * @param {{additionalTraceCategories?: string|null}=} settings
    * @return {Promise<void>}

core/legacy/gather/gather-runner.js

@@ -313,17 +313,12 @@ class GatherRunner {
    * @return {Promise<void>}
    */
   static async afterPass(passContext, loadData, gathererResults) {
-    const driver = passContext.driver;
     const config = passContext.passConfig;
     const gatherers = config.gatherers;
 
     const apStatus = {msg: `Running afterPass methods`, id: `lh:gather:afterPass`};
     log.time(apStatus, 'verbose');
 
-    // Some gatherers scroll the page which can cause unexpected results for other gatherers.
-    // We reset the scroll position in between each gatherer.
-    const scrollPosition = await driver.getScrollPosition();
-
     for (const gathererDefn of gatherers) {
       const gatherer = gathererDefn.instance;
       const status = {
@@ -339,7 +334,6 @@ class GatherRunner {
       gathererResult.push(artifactPromise);
       gathererResults[gatherer.name] = gathererResult;
       await artifactPromise.catch(() => {});
-      await driver.scrollTo(scrollPosition);
       log.timeEnd(status);
     }
     log.timeEnd(apStatus);

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

@@ -10,8 +10,6 @@ import {fnAny, readJson} from '../../test-utils.js';
  * @param {{protocolGetVersionResponse: LH.CrdpCommands['Browser.getVersion']['returnType']}} param0
  */
 function makeFakeDriver({protocolGetVersionResponse}) {
-  let scrollPosition = {x: 0, y: 0};
-
   return {
     get fetcher() {
       return {};
@@ -56,14 +54,6 @@ function makeFakeDriver({protocolGetVersionResponse}) {
         return Promise.resolve();
       },
     },
-    /** @param {{x: number, y: number}} position */
-    scrollTo(position) {
-      scrollPosition = position;
-      return Promise.resolve();
-    },
-    getScrollPosition() {
-      return Promise.resolve(scrollPosition);
-    },
     beginTrace() {
       return Promise.resolve();
     },

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

@@ -687,40 +687,6 @@ describe('GatherRunner', function() {
     });
   });
 
-  it('resets scroll position between every gatherer', async () => {
-    class ScrollMcScrollyGatherer extends TestGatherer {
-      /** @param {{driver: Driver}} context */
-      afterPass(context) {
-        context.driver.scrollTo({x: 1000, y: 1000});
-      }
-    }
-
-    const url = 'https://example.com';
-    const driver = Object.assign({}, fakeDriver);
-    const scrollToSpy = jestMock.spyOn(driver, 'scrollTo');
-
-    const passConfig = {
-      recordTrace: true,
-      gatherers: [
-        {instance: new ScrollMcScrollyGatherer()},
-        {instance: new TestGatherer()},
-      ],
-    };
-
-    /** @type {any} Using Test-only gatherer. */
-    const gathererResults = {
-      TestGatherer: [],
-    };
-    const passContext = {url, driver, passConfig, computedCache: new Map()};
-    await GatherRunner.afterPass(passContext, {}, gathererResults);
-    // One time for the afterPass of ScrollMcScrolly, two times for the resets of the two gatherers.
-    expect(scrollToSpy.mock.calls).toEqual([
-      [{x: 1000, y: 1000}],
-      [{x: 0, y: 0}],
-      [{x: 0, y: 0}],
-    ]);
-  });
-
   it('does as many passes as are required', async () => {
     const t1 = new TestGatherer();
     const t2 = new TestGatherer();