Allow disabling the alternative backlink labels message

The message cite_references_link_many_format_backlink_labels contains
e.g. "a b c …" and so on, to be used as alternative backlink labels
when a single reference is re-used multiple times. The default numeric
rendering is "1.1 1.2 …" and so on.

The two labels end in the message cite_references_link_many_format as
parameters $2 and $3. But only one of the two parameters is ever used.
By default the alternative label in $3 is unused.

This implies that everything about these alternative backlink labels
including the error message is effectively dead code most of the time,
never to be seen on the majority of wikis.

This change makes it possible to disable the message without breaking
anything. Instead the code will silently fallback to the default
behavior of showing the numeric label. This is much more efficient
than rendering possibly hundreds of error messages that never show
up anyhere. The same optimization is already done for the extremely
similar cite_link_label_group-… messages, see
FootnoteMarkFormatter::fetchCustomizedLinkLabel.

This is also partly motivated by T335129 as well as T321217.

Change-Id: Iab818d7db7eddaf7091234f6a22a18cdff70f8e8

i18n/qqq.json

@@ -57,8 +57,8 @@
 	"cite_reference_link": "{{notranslate}}\n\nParameters:\n* $1 - ref key\n* $2 - references key\n* $3 - link label",
 	"cite_references_link_one": "{{notranslate}}\n\nParameters:\n* $1 - references key\n* $2 - ref key\n* $3 - reference text\n* $4 - optional CSS class for direction",
 	"cite_references_link_many": "{{notranslate}}\n\nParameters:\n* $1 - references key\n* $2 - list of links\n* $3 - reference text\n* $4 - optional CSS class for direction",
-	"cite_references_link_many_format": "{{notranslate}}\n\nParameters:\n* $1 - reference key\n* $2 - canonical numeric backlink label for the link, always in the form \"1.2\"\n* $3 - optional alternate backlink label as defined via [[MediaWiki:cite_references_link_many_format_backlink_labels]]",
-	"cite_references_link_many_format_backlink_labels": "{{Optional}}",
+	"cite_references_link_many_format": "{{notranslate}}\n\nParameters:\n* $1 - Reference key\n* $2 - Canonical numerical label for the backlink, always in the form \"1.1\", \"1.2\", and so on.\n* $3 - Alternative alphabetic label for the backlink as defined via [[MediaWiki:cite_references_link_many_format_backlink_labels]], typically \"a\", \"b\", and so on.",
+	"cite_references_link_many_format_backlink_labels": "{{optional}}\nAlternative alphabetic backlink labels for use in the [[MediaWiki:cite_references_link_many_format]] message as parameter $3. Should only be customized when the alphabet is not identical to the 26 basic Latin characters \"a\" to \"z\". Make sure to include at least as many labels as in the default sequence \"a\" to \"zz\" (702 labels), possibly even more. E.g. adding \"aaa\" to \"azz\" gives 1378 total. This message can be disabled if not needed.",
 	"cite_references_link_many_sep": "{{notranslate}}",
 	"cite_references_link_many_and": "{{optional}}",
 	"cite_references_link_accessibility_label": "Text for screen readers to describe the jump to citation link (\"↑\").\n\nSee also:\n* {{msg-mw|Cite references link many accessibility label}} - if the citation is used multiple times",

src/ReferenceListFormatter.php

@@ -184,16 +184,16 @@ class ReferenceListFormatter {
 		// Named references with >1 occurrences
 		$backlinks = [];
 		for ( $i = 0; $i < $ref->count; $i++ ) {
+			$numericLabel = $this->referencesFormatEntryNumericBacklinkLabel(
+				$ref->number . ( $ref->extendsIndex ? '.' . $ref->extendsIndex : '' ),
+				$i,
+				$ref->count
+			);
 			$backlinks[] = $this->messageLocalizer->msg(
 				'cite_references_link_many_format',
 				$this->anchorFormatter->backLink( $key, $ref->key . '-' . $i ),
-				$this->referencesFormatEntryNumericBacklinkLabel(
-					$ref->number .
-						( isset( $ref->extendsIndex ) ? '.' . $ref->extendsIndex : '' ),
-					$i,
-					$ref->count
-				),
-				$this->referencesFormatEntryAlternateBacklinkLabel( $parser, $i )
+				$numericLabel,
+				$this->referencesFormatEntryAlternateBacklinkLabel( $parser, $i ) ?? $numericLabel
 			)->plain();
 		}
 		$linkTargetId = $ref->count > 0 ?
@@ -267,12 +267,16 @@ class ReferenceListFormatter {
 	 */
 	private function referencesFormatEntryAlternateBacklinkLabel(
 		Parser $parser, int $offset
-	): string {
-		$this->backlinkLabels ??= preg_split(
-			'/\s+/',
-			$this->messageLocalizer->msg( 'cite_references_link_many_format_backlink_labels' )
-				->plain()
-		);
+	): ?string {
+		if ( !isset( $this->backlinkLabels ) ) {
+			$msg = $this->messageLocalizer->msg( 'cite_references_link_many_format_backlink_labels' );
+			$this->backlinkLabels = $msg->isDisabled() ? [] : preg_split( '/\s+/', $msg->plain() );
+		}
+
+		// Disabling the message just disables the feature
+		if ( !$this->backlinkLabels ) {
+			return null;
+		}
 
 		return $this->backlinkLabels[$offset]
 			?? $this->errorReporter->plain( $parser, 'cite_error_references_no_backlink_label' );

tests/phpunit/unit/ReferenceListFormatterTest.php

@@ -353,7 +353,8 @@ class ReferenceListFormatterTest extends \MediaWikiUnitTestCase {
 	public function testReferencesFormatEntryAlternateBacklinkLabel(
 		?string $expectedLabel, string $labelList, int $offset
 	) {
-		$mockMessage = $this->createNoOpMock( Message::class, [ 'plain' ] );
+		$mockMessage = $this->createNoOpMock( Message::class, [ 'isDisabled', 'plain' ] );
+		$mockMessage->method( 'isDisabled' )->willReturn( !$labelList );
 		$mockMessage->method( 'plain' )->willReturn( $labelList );
 
 		$mockMessageLocalizer = $this->createMock( ReferenceMessageLocalizer::class );
@@ -361,8 +362,7 @@ class ReferenceListFormatterTest extends \MediaWikiUnitTestCase {
 			->willReturn( $mockMessage );
 
 		$errorReporter = $this->createMock( ErrorReporter::class );
-		$errorReporter->expects( $expectedLabel ? $this->never() : $this->once() )
-			->method( 'plain' );
+		$errorReporter->method( 'plain' )->willReturnArgument( 1 );
 
 		/** @var ReferenceListFormatter $formatter */
 		$formatter = TestingAccessWrapper::newFromObject( new ReferenceListFormatter(
@@ -373,16 +373,15 @@ class ReferenceListFormatterTest extends \MediaWikiUnitTestCase {
 
 		$parser = $this->createNoOpMock( Parser::class );
 		$label = $formatter->referencesFormatEntryAlternateBacklinkLabel( $parser, $offset );
-		if ( $expectedLabel !== null ) {
-			$this->assertSame( $expectedLabel, $label );
-		}
+		$this->assertSame( $expectedLabel, $label );
 	}
 
 	public static function provideReferencesFormatEntryAlternateBacklinkLabel() {
 		yield [ 'aa', 'aa ab ac', 0 ];
 		yield [ 'ab', 'aa ab ac', 1 ];
 		yield [ 'å', 'å b c', 0 ];
-		yield [ null, 'a b c', 10 ];
+		yield [ 'cite_error_references_no_backlink_label', 'a b c', 10 ];
+		yield [ null, '', 0 ];
 	}
 
 	/**