Sticky header edit button A/B test bucketing

Adds behaviour for conditionally adding the edit button
to the sticky-header based on A/B test bucketing.

This behaviour depends on having the `$wgVectorStickyHeaderEdit` config
set to true for logged-in users:

    $wgVectorStickyHeaderEdit = [
        "logged_in" => true,
        "logged_out" => false
    ];

as well as an AB test configured with the following buckets:

    $wgVectorWebABTestEnrollment = [
        'name' => 'vector.sticky_header_edit',
        'enabled' => true,
        'buckets' => [
            'unsampled' => [
                'samplingRate' => 0
            ],
            'stickyHeaderEditButtonControl' => [
                'samplingRate' => 0
            ],
            'stickyHeaderEditButtonTreatment' => [
                'samplingRate' => 1
            ]
        ]
    ];

With that config, this change hides the sticky header for all users
except those in the stickyHeaderEditButtonTreatment bucket.

Bug: T299959
Change-Id: If252956bc530d8ce54eeda61f42a93ffa48255cb

resources/skins.vector.es6/main.js

@@ -71,26 +71,65 @@ const main = () => {
 		allowedAction &&
 		'IntersectionObserver' in window;
 
-	const isExperimentEnabled =
+	/**
-		!!ABTestConfig.enabled &&
+	 * Initialize sticky header AB tests and determine whether to show the sticky header
-		ABTestConfig.name === stickyHeader.STICKY_HEADER_EXPERIMENT_NAME &&
+	 * based on which buckets the user is in.
-		!mw.user.isAnon() &&
+	 *
-		isStickyHeaderAllowed;
+	 * @typedef {Object} InitStickyHeaderABTests
+	 * @property {boolean} disableEditIcons - Should the sticky header have an edit icon
+	 * @property {boolean} showStickyHeader - Should the sticky header be shown
+	 * @return {InitStickyHeaderABTests}
+	 */
+	function initStickyHeaderABTests() {
 
-	// If necessary, initialize experiment and fire the A/B test enrollment hook.
+		let show = isStickyHeaderAllowed,
-	const stickyHeaderExperiment = isExperimentEnabled &&
+			stickyHeaderExperiment,
-		initExperiment( Object.assign( {}, ABTestConfig, { token: mw.user.getId() } ) );
+			noEditIcons = true;
+
+		// Determine if user is eligible for sticky header AB test
+		if (
+			isStickyHeaderAllowed && // The sticky header can be shown on the page
+			ABTestConfig.enabled && // An AB test config is enabled
+			!mw.user.isAnon() && // The user is logged-in
+			( // One of the sticky-header AB tests is specified in the config
+				ABTestConfig.name === stickyHeader.STICKY_HEADER_EXPERIMENT_NAME ||
+				ABTestConfig.name === 'vector.sticky_header_edit'
+			)
+		) {
+			// If eligible, initialize the AB test
+			stickyHeaderExperiment = initExperiment(
+				Object.assign( {}, ABTestConfig, { token: mw.user.getId() } )
+			);
+
+			// If running initial AB test, only show sticky header to treatment group.
+			if ( stickyHeaderExperiment.name === stickyHeader.STICKY_HEADER_EXPERIMENT_NAME ) {
+				show = stickyHeaderExperiment.isInTreatmentBucket();
+			}
+
+			// If running edit-button AB test, show sticky header to all buckets
+			// and show edit button for treatment group
+			if ( stickyHeaderExperiment.name === 'vector.sticky_header_edit' ) {
+				show = true;
+				if ( stickyHeaderExperiment.isInTreatmentBucket() ) {
+					noEditIcons = false;
+				}
+			}
+		}
+
+		return {
+			showStickyHeader: show,
+			disableEditIcons: noEditIcons
+		};
+	}
+
+	const { showStickyHeader, disableEditIcons } = initStickyHeaderABTests();
 
 	// Remove class if present on the html element so that scroll padding isn't undesirably
 	// applied to users who don't experience the new treatment.
-	if ( stickyHeaderExperiment && !stickyHeaderExperiment.isInTreatmentBucket() ) {
+	if ( !showStickyHeader ) {
 		document.documentElement.classList.remove( 'vector-sticky-header-enabled' );
 	}
 
-	const isStickyHeaderEnabled = stickyHeaderExperiment ?
-		stickyHeaderExperiment.isInTreatmentBucket() :
-		isStickyHeaderAllowed;
-
 	// Table of contents
 	const tocElement = document.getElementById( TOC_ID );
 	const tocElementLegacy = document.getElementById( TOC_ID_LEGACY );
@@ -99,25 +138,26 @@ const main = () => {
 	// Set up intersection observer for page title, used by sticky header
 	const observer = scrollObserver.initScrollObserver(
 		() => {
-			if ( isStickyHeaderAllowed && isStickyHeaderEnabled ) {
+			if ( isStickyHeaderAllowed && showStickyHeader ) {
 				stickyHeader.show();
 			}
 			scrollObserver.fireScrollHook( 'down', PAGE_TITLE_SCROLL_HOOK );
 		},
 		() => {
-			if ( isStickyHeaderAllowed && isStickyHeaderEnabled ) {
+			if ( isStickyHeaderAllowed && showStickyHeader ) {
 				stickyHeader.hide();
 			}
 			scrollObserver.fireScrollHook( 'up', PAGE_TITLE_SCROLL_HOOK );
 		}
 	);
 
-	if ( isStickyHeaderAllowed && isStickyHeaderEnabled ) {
+	if ( isStickyHeaderAllowed && showStickyHeader ) {
 		stickyHeader.initStickyHeader( {
 			header,
 			userMenu,
 			observer,
-			stickyIntersection
+			stickyIntersection,
+			disableEditIcons
 		} );
 	} else if ( stickyIntersection ) {
 		observer.observe( stickyIntersection );

resources/skins.vector.es6/stickyHeader.js

@@ -212,6 +212,7 @@ function prepareEditIcons(
 	if ( !primaryEditSticky || !wikitextSticky || !protectedSticky ) {
 		return;
 	}
+
 	if ( !primaryEdit ) {
 		removeNode( protectedSticky );
 		removeNode( wikitextSticky );
@@ -343,13 +344,15 @@ function prepareUserMenu( userMenu ) {
  * @param {Element} userMenuStickyContainer
  * @param {IntersectionObserver} stickyObserver
  * @param {Element} stickyIntersection
+ * @param {boolean} disableEditIcons
  */
 function makeStickyHeaderFunctional(
 	header,
 	userMenu,
 	userMenuStickyContainer,
 	stickyObserver,
-	stickyIntersection
+	stickyIntersection,
+	disableEditIcons
 ) {
 	const
 		userMenuStickyContainerInner = userMenuStickyContainer
@@ -370,7 +373,9 @@ function makeStickyHeaderFunctional(
 	const ceEdit = document.querySelector( '#ca-edit a' );
 	const protectedEdit = document.querySelector( '#ca-viewsource a' );
 	const isProtected = !!protectedEdit;
-	const primaryEdit = protectedEdit || ( veEdit || ceEdit );
+	// For sticky header edit A/B test, conditionally remove the edit icon by setting null.
+	// Otherwise, use either protected, ve, or source edit (in that order).
+	const primaryEdit = disableEditIcons ? null : protectedEdit || veEdit || ceEdit;
 	const secondaryEdit = veEdit ? ceEdit : null;
 	const disableStickyHeader = () => {
 		document.body.classList.remove( STICKY_HEADER_VISIBLE_CLASS );
@@ -434,6 +439,7 @@ function isAllowedAction( action ) {
  * @property {Element} userMenu
  * @property {IntersectionObserver} observer
  * @property {Element} stickyIntersection
+ * @property {boolean} disableEditIcons
  */
 
 /**
@@ -449,7 +455,8 @@ function initStickyHeader( props ) {
 		props.userMenu,
 		userMenuStickyContainer,
 		props.observer,
-		props.stickyIntersection
+		props.stickyIntersection,
+		props.disableEditIcons
 	);
 
 	setupSearchIfNeeded( props.header );