Add ext.popups.experiment module

Changes:
* Add the ext.popups.experiment module
* Add the mw.popups.experiment.isUserInCondition function, which
  returns a promise that resolves with true if the user is in the
  experimental condition, otherwise false
* If the experiment isn't configured, i.e. wgPopupsExperimentConfig is
  null or undefined, then the user isn't entered into the experiment,
  providing a kill switch

Bug: T132604
Change-Id: I49597494273e3862711a32e4951c8598e6c8bf59

Popups.hooks.php

@@ -223,8 +223,12 @@ class PopupsHooks {
 				'tests/qunit/ext.popups.renderer.article.test.js',
 				'tests/qunit/ext.popups.core.test.js',
 				'tests/qunit/ext.popups.settings.test.js',
+				'tests/qunit/ext.popups.experiment.test.js',
+			),
+			'dependencies' => array(
+				'ext.popups.desktop',
+				'ext.popups.experiment'
 			),
-			'dependencies' => array( 'ext.popups.desktop' ),
 			'localBasePath' => __DIR__,
 			'remoteExtPath' => 'Popups',
 		);

extension.json

@@ -92,6 +92,21 @@
 			"dependencies": [
 				"ext.popups.core"
 			]
+		},
+		"ext.popups.experiment": {
+			"scripts": [
+				"resources/ext.popups.experiment.js"
+			],
+			"dependencies": [
+				"ext.popups.core",
+				"jquery.jStorage",
+				"mediawiki.user",
+				"mediawiki.storage",
+				"mediawiki.experiments"
+			],
+			"targets": [
+				"desktop"
+			]
 		}
 	},
 	"ResourceFileModulePaths": {

resources/ext.popups.experiment.js

@@ -0,0 +1,79 @@
+( function ( mw, $ ) {
+
+	/**
+	 * @ignore
+	 */
+	function getToken() {
+		var key = 'PopupsExperimentID',
+			id = mw.storage.get( key );
+
+		if ( !id ) {
+			id = mw.user.generateRandomSessionId();
+
+			mw.storage.set( key, id );
+		}
+
+		return id;
+	}
+
+	/**
+	 * Has the user previously enabled Popups by clicking "Enable previews" in the
+	 * footer menu?
+	 *
+	 * @return {boolean}
+	 * @ignore
+	 */
+	function hasUserEnabledFeature() {
+		var value = $.jStorage.get( 'mwe-popups-enabled' );
+
+		return Boolean( value ) && value !== 'false';
+	}
+
+	/**
+	 * @class mw.popups.experiment
+	 * @singleton
+	 */
+	mw.popups.experiment = {};
+
+	/**
+	 * Gets whether or not the user has Popups enabled, i.e. whether they are in the experiment
+	 * condition.
+	 *
+	 * The user is in the experiment condition if:
+	 * * they've enabled Popups by click "Enable previews" in the footer menu, or
+	 * * they've enabled Popups as a beta feature, or
+	 * * they aren't in the control bucket of the experiment
+	 *
+	 * N.B. that the user isn't entered into the experiment, i.e. they aren't assigned or a bucket,
+	 * if the experiment isn't configured.
+	 *
+	 * @return {jQuery.Promise}
+	 */
+	mw.popups.experiment.isUserInCondition = function isUserInCondition() {
+		var deferred = $.Deferred(),
+				config = mw.config.get( 'wgPopupsExperimentConfig' ),
+				result;
+
+		if (
+			hasUserEnabledFeature() ||
+
+			// Users with the beta feature enabled are already in the experimental condition.
+			mw.config.get( 'wgPopupsExperimentIsBetaFeatureEnabled', false )
+		) {
+			deferred.resolve( true );
+		} else if ( !config ) {
+			deferred.resolve( false );
+		} else {
+			mw.requestIdleCallback( function () {
+				// FIXME: mw.experiments should expose the CONTROL_BUCKET constant, e.g.
+				// `mw.experiments.CONTROL_BUCKET`.
+				result = mw.experiments.getBucket( config, getToken() ) !== 'control';
+
+				deferred.resolve( result );
+			} );
+		}
+
+		return deferred.promise();
+	};
+
+}( mediaWiki, jQuery ) );

tests/qunit/ext.popups.experiment.test.js

@@ -0,0 +1,112 @@
+( function ( mw, $ ) {
+
+	QUnit.module( 'ext.popups.experiment', QUnit.newMwEnvironment( {
+		config: {
+			wgPopupsExperimentConfig: {
+				name: 'Popups A/B Test - May, 2016',
+				enabled: true,
+				buckets: {
+					control: 0.5,
+					A: 0.5
+				}
+			}
+		},
+		teardown: function () {
+			mw.storage.remove( 'PopupsExperimentID' );
+		}
+	} ) );
+
+	QUnit.test( '#isUserInCondition: user has beta feature enabled', function ( assert ) {
+		var done = assert.async();
+
+		mw.config.set( 'wgPopupsExperimentConfig', null );
+		mw.config.set( 'wgPopupsExperimentIsBetaFeatureEnabled', true );
+
+		mw.popups.experiment.isUserInCondition().then( function ( result ) {
+			assert.strictEqual(
+				result,
+				true,
+				'If the user has the beta feature enabled, then they aren\'t in the condition.'
+			);
+
+			done();
+		} );
+	} );
+
+	QUnit.test( '#isUserInCondition', function ( assert ) {
+		var getBucketSpy = this.sandbox.stub( mw.experiments, 'getBucket' ).returns( 'A' ),
+			config = mw.config.get( 'wgPopupsExperimentConfig' ),
+			done = assert.async();
+
+		mw.popups.experiment.isUserInCondition().then( function ( result ) {
+			var fistCallArgs = getBucketSpy.firstCall.args;
+
+			assert.deepEqual(
+				fistCallArgs[ 0 ],
+				config,
+				'The Popups experiment config is used when bucketing the user.'
+			);
+
+			assert.strictEqual(
+				result,
+				true,
+				'If the user isn\'t in the control bucket, then they are in the condition.'
+			);
+
+			done();
+		} );
+	} );
+
+	QUnit.test( '#isUserInCondition: token is persisted', function ( assert ) {
+		var token = '1234567890',
+			setSpy = this.sandbox.spy( mw.storage, 'set' ),
+			done = assert.async();
+
+		this.sandbox.stub( mw.user, 'generateRandomSessionId' ).returns( token );
+
+		mw.popups.experiment.isUserInCondition().then( function () {
+			assert.deepEqual(
+				setSpy.firstCall.args[ 1 ],
+				token,
+				'The token is persisted transparently.'
+			);
+
+			done();
+		} );
+	} );
+
+	QUnit.test( '#isUserInCondition: experiment isn\'t configured', function ( assert ) {
+		var done = assert.async();
+
+		mw.config.set( 'wgPopupsExperimentConfig', null );
+
+		mw.popups.experiment.isUserInCondition().then( function ( result ) {
+			assert.strictEqual(
+				result,
+				false,
+				'If the experiment isn\'t configured, then the user isn\'t in the condition.'
+			);
+
+			done();
+		} );
+	} );
+
+	QUnit.test( '#isUserInCondition: user has enabled the feature', function ( assert ) {
+		var done = assert.async();
+
+		$.jStorage.set( 'mwe-popups-enabled', 'true' );
+
+		mw.popups.experiment.isUserInCondition().then( function ( result ) {
+			assert.strictEqual(
+				result,
+				true,
+				'If the experiment has enabled the feature, then the user is in the condition.'
+			);
+
+			$.jStorage.deleteKey( 'mwe-popups-enabled' );
+
+			done();
+		} );
+	} );
+
+}( mediaWiki, jQuery ) );