From de5a640c0b3bff2b82765c10aeab27d27e3a8966 Mon Sep 17 00:00:00 2001
From: Nicholas Ray <nray@wikimedia.org>
Date: Thu, 13 May 2021 11:55:20 -0600
Subject: [PATCH] Allow `languageinheader` query param to fully control
 treatment of languages

Before this commit the `languageinheader` query param would only take
effect if the A/B test was enabled AND the query param was set. Per
T282543, we want the query param to take effect regardless of the state
of the language/AB test config.

To see new treatment, set `languageinheader=1`.
To see old treatment, set `languageinheader=0`.

Bug: T282543
Change-Id: I6a06e90b6e46a6fd7506a5ddeaf071b893ebfe8e
---
 .../LanguageInHeaderTreatmentRequirement.php  |  9 +++---
 ...nguageInHeaderTreatmentRequirementTest.php | 32 +++++++++++++++++++
 2 files changed, 36 insertions(+), 5 deletions(-)

diff --git a/includes/FeatureManagement/Requirements/LanguageInHeaderTreatmentRequirement.php b/includes/FeatureManagement/Requirements/LanguageInHeaderTreatmentRequirement.php
index 6ce703c..128620e 100644
--- a/includes/FeatureManagement/Requirements/LanguageInHeaderTreatmentRequirement.php
+++ b/includes/FeatureManagement/Requirements/LanguageInHeaderTreatmentRequirement.php
@@ -91,15 +91,14 @@ final class LanguageInHeaderTreatmentRequirement implements Requirement {
 	 * @throws \ConfigException
 	 */
 	public function isMet() : bool {
+		if ( $this->request->getCheck( Constants::QUERY_PARAM_LANGUAGE_IN_HEADER ) ) {
+			return $this->request->getBool( Constants::QUERY_PARAM_LANGUAGE_IN_HEADER );
+		}
+
 		if (
 			(bool)$this->config->get( Constants::CONFIG_LANGUAGE_IN_HEADER_TREATMENT_AB_TEST ) &&
 			$this->user->isRegistered()
 		) {
-
-			if ( $this->request->getCheck( Constants::QUERY_PARAM_LANGUAGE_IN_HEADER ) ) {
-				return $this->request->getBool( Constants::QUERY_PARAM_LANGUAGE_IN_HEADER );
-			}
-
 			$id = null;
 			if ( $this->centralIdLookup ) {
 				$id = $this->centralIdLookup->centralIdFromLocalUser( $this->user );
diff --git a/tests/phpunit/unit/FeatureManagement/Requirements/LanguageInHeaderTreatmentRequirementTest.php b/tests/phpunit/unit/FeatureManagement/Requirements/LanguageInHeaderTreatmentRequirementTest.php
index a042989..df0a04c 100644
--- a/tests/phpunit/unit/FeatureManagement/Requirements/LanguageInHeaderTreatmentRequirementTest.php
+++ b/tests/phpunit/unit/FeatureManagement/Requirements/LanguageInHeaderTreatmentRequirementTest.php
@@ -234,6 +234,38 @@ class LanguageInHeaderTreatmentRequirementTest extends \MediaWikiUnitTestCase {
 				false,
 				'Even logged in users get old treatment when A/B test enabled and query param set to "0"'
 			],
+			[
+				// Is language enabled
+				[
+					'logged_in' => false,
+					'logged_out' => false,
+				],
+				// is A-B test enabled
+				false,
+				1,
+				// use central id lookup?
+				false,
+				// `languageinheader` query param
+				"1",
+				true,
+				'Users get new treatment when query param set to "1" regardless of state of A/B test or config flags'
+			],
+			[
+				// Is language enabled
+				[
+					'logged_in' => false,
+					'logged_out' => false,
+				],
+				// is A-B test enabled
+				false,
+				1,
+				// use central id lookup?
+				false,
+				// `languageinheader` query param
+				"0",
+				false,
+				'Users get old treatment when query param set to "0" regardless of state of A/B test or config flags'
+			],
 		];
 	}