From a2415baa1a3c94abe83d0e2af274c4753775515e Mon Sep 17 00:00:00 2001
From: Brad Jorsch <bjorsch@wikimedia.org>
Date: Fri, 1 May 2015 11:05:32 -0400
Subject: [PATCH] ChangeTags: Don't show UI when no editable tags exist

Bug: T97773
Change-Id: I001f15ca6f58bc9318eed84aa8ace2bddcb1b315
---
 includes/actions/HistoryAction.php |  8 ++++----
 includes/changetags/ChangeTags.php | 18 ++++++++++++++++++
 includes/logging/LogEventsList.php |  2 +-
 includes/specials/SpecialLog.php   |  6 +++---
 4 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/includes/actions/HistoryAction.php b/includes/actions/HistoryAction.php
index 83185e4d61..f4f2a2a18c 100644
--- a/includes/actions/HistoryAction.php
+++ b/includes/actions/HistoryAction.php
@@ -504,7 +504,7 @@ class HistoryPager extends ReverseChronologicalPager {
 		if ( $user->isAllowed( 'deleterevision' ) ) {
 			$actionButtons .= $this->getRevisionButton( 'revisiondelete', 'showhideselectedversions' );
 		}
-		if ( $user->isAllowed( 'changetags' ) ) {
+		if ( ChangeTags::showTagEditingUI( $user ) ) {
 			$actionButtons .= $this->getRevisionButton( 'editchangetags', 'history-edit-tags' );
 		}
 		if ( $actionButtons ) {
@@ -631,14 +631,14 @@ class HistoryPager extends ReverseChronologicalPager {
 		$del = '';
 		$user = $this->getUser();
 		$canRevDelete = $user->isAllowed( 'deleterevision' );
-		$canModifyTags = $user->isAllowed( 'changetags' );
+		$showTagEditUI = ChangeTags::showTagEditingUI( $user );
 		// Show checkboxes for each revision, to allow for revision deletion and
 		// change tags
-		if ( $canRevDelete || $canModifyTags ) {
+		if ( $canRevDelete || $showTagEditUI ) {
 			$this->preventClickjacking();
 			// If revision was hidden from sysops and we don't need the checkbox
 			// for anything else, disable it
-			if ( !$canModifyTags && !$rev->userCan( Revision::DELETED_RESTRICTED, $user ) ) {
+			if ( !$showTagEditUI && !$rev->userCan( Revision::DELETED_RESTRICTED, $user ) ) {
 				$del = Xml::check( 'deleterevisions', false, array( 'disabled' => 'disabled' ) );
 			// Otherwise, enable the checkbox...
 			} else {
diff --git a/includes/changetags/ChangeTags.php b/includes/changetags/ChangeTags.php
index cf33484f0b..564feb6509 100644
--- a/includes/changetags/ChangeTags.php
+++ b/includes/changetags/ChangeTags.php
@@ -1220,4 +1220,22 @@ class ChangeTags {
 		$wgMemc->set( $key, $out, 300 );
 		return $out;
 	}
+
+	/**
+	 * Indicate whether change tag editing UI is relevant
+	 *
+	 * Returns true if the user has the necessary right and there are any
+	 * editable tags defined.
+	 *
+	 * This intentionally doesn't check "any addable || any deletable", because
+	 * it seems like it would be more confusing than useful if the checkboxes
+	 * suddenly showed up because some abuse filter stopped defining a tag and
+	 * then suddenly disappeared when someone deleted all uses of that tag.
+	 *
+	 * @param User $user
+	 * @return bool
+	 */
+	public static function showTagEditingUI( User $user ) {
+		return $user->isAllowed( 'changetags' ) && (bool)self::listExplicitlyDefinedTags();
+	}
 }
diff --git a/includes/logging/LogEventsList.php b/includes/logging/LogEventsList.php
index dcddbd776b..dfe31365af 100644
--- a/includes/logging/LogEventsList.php
+++ b/includes/logging/LogEventsList.php
@@ -348,7 +348,7 @@ class LogEventsList extends ContextSource {
 		$user = $this->getUser();
 
 		// If change tag editing is available to this user, return the checkbox
-		if ( $this->flags & self::USE_CHECKBOXES && $user->isAllowed( 'changetags' ) ) {
+		if ( $this->flags & self::USE_CHECKBOXES && ChangeTags::showTagEditingUI( $user ) ) {
 			return Xml::check(
 				'showhiderevisions',
 				false,
diff --git a/includes/specials/SpecialLog.php b/includes/specials/SpecialLog.php
index fe6ce68d27..e44ce5f5b2 100644
--- a/includes/specials/SpecialLog.php
+++ b/includes/specials/SpecialLog.php
@@ -218,10 +218,10 @@ class SpecialLog extends SpecialPage {
 	private function getActionButtons( $formcontents ) {
 		$user = $this->getUser();
 		$canRevDelete = $user->isAllowedAll( 'deletedhistory', 'deletelogentry' );
-		$canModifyTags = $user->isAllowed( 'changetags' );
+		$showTagEditUI = ChangeTags::showTagEditingUI( $user );
 		# If the user doesn't have the ability to delete log entries nor edit tags,
 		# don't bother showing them the button(s).
-		if ( !$canRevDelete && !$canModifyTags ) {
+		if ( !$canRevDelete && !$showTagEditUI ) {
 			return $formcontents;
 		}
 
@@ -246,7 +246,7 @@ class SpecialLog extends SpecialPage {
 				$this->msg( 'showhideselectedlogentries' )->text()
 			) . "\n";
 		}
-		if ( $canModifyTags ) {
+		if ( $showTagEditUI ) {
 			$buttons .= Html::element(
 				'button',
 				array(
-- 
2.20.1