From 775fec5450df8a2d10bedc6f8b578ff449d2c9ba Mon Sep 17 00:00:00 2001
From: physikerwelt <wiki@physikerwelt.de>
Date: Wed, 6 Nov 2024 23:04:13 +0100
Subject: [PATCH] Treat \operatorname as a valid operator for limits

* Extend logic for checking for valid operators
* Add tests

Bug: T365170
Change-Id: I4d3762e3258c78ac5fae8b923f12aabcd2175f3d
---
 src/WikiTexVC/Nodes/TexArray.php              | 13 ++++++++++---
 .../unit/WikiTexVC/Nodes/TexArrayTest.php     | 19 +++++++++++++++++++
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/src/WikiTexVC/Nodes/TexArray.php b/src/WikiTexVC/Nodes/TexArray.php
index e8480e0bf..9de11c858 100644
--- a/src/WikiTexVC/Nodes/TexArray.php
+++ b/src/WikiTexVC/Nodes/TexArray.php
@@ -128,9 +128,16 @@ class TexArray extends TexNode implements \ArrayAccess, \IteratorAggregate {
 		$tu = TexUtil::getInstance();
 
 		// Check whether the current node is a possible preceding literal
-		if ( !( $currentNode instanceof Literal
-			&& ( $tu->nullary_macro( trim( $currentNode->getArg() ) )
-			|| trim( $currentNode->getArg() ) == "\\lim" ) ) ) {
+		if ( !(
+		// logically superfluous brackets were inserted to improve readability
+		( $currentNode instanceof Literal &&
+				// Check if the current node is a nullary macro such as \iint, \sum, \prod, etc.
+				( $tu->nullary_macro( trim( $currentNode->getArg() ) )
+				// or a limit operator
+				|| ( trim( $currentNode->getArg() ) == "\\lim" ) ) ) ||
+		// or the special case of \operatorname
+		( $currentNode instanceof Fun1nb && $currentNode->getFname() == "\\operatorname" )
+		) ) {
 			return [ null, false ];
 		}
 
diff --git a/tests/phpunit/unit/WikiTexVC/Nodes/TexArrayTest.php b/tests/phpunit/unit/WikiTexVC/Nodes/TexArrayTest.php
index a017623b2..ab1e3cba4 100644
--- a/tests/phpunit/unit/WikiTexVC/Nodes/TexArrayTest.php
+++ b/tests/phpunit/unit/WikiTexVC/Nodes/TexArrayTest.php
@@ -3,6 +3,8 @@
 namespace MediaWiki\Extension\Math\Tests\WikiTexVC\Nodes;
 
 use InvalidArgumentException;
+use MediaWiki\Extension\Math\WikiTexVC\Nodes\DQ;
+use MediaWiki\Extension\Math\WikiTexVC\Nodes\Fun1nb;
 use MediaWiki\Extension\Math\WikiTexVC\Nodes\Literal;
 use MediaWiki\Extension\Math\WikiTexVC\Nodes\TexArray;
 use MediaWiki\Extension\Math\WikiTexVC\Nodes\TexNode;
@@ -132,4 +134,21 @@ class TexArrayTest extends MediaWikiUnitTestCase {
 		$res  = $ta->renderMML( [], [ 'squashLiterals' => true ] );
 		$this->assertEquals( '<mi>a</mi><mi>&#x03B3;</mi>', $res );
 	}
+
+	public function testSumInLimits() {
+		$ta = new TexArray();
+		$sum = new Literal( '\sum' );
+		$res  = $ta->checkForLimits( $sum, new DQ( new Literal( '\limits' ), new Literal( 'n' ) ) );
+		$this->assertTrue( $res[1] );
+		$this->assertEquals( $sum, $res[0] );
+	}
+
+	public function testCustomOpInLimits() {
+		$ta = new TexArray();
+		$custom = new Fun1nb( '\operatorname', new TexArray( new Literal( 'S' ) ) );
+		$res  = $ta->checkForLimits( $custom, new DQ( new Literal( '\limits' ), new Literal( 'n' ) ) );
+		$this->assertTrue( $res[1] );
+		$this->assertEquals( $custom, $res[0] );
+	}
+
 }