parser: Gracefully handle invalid ParsoidRenderID keys

Why:

- ParsoidRenderID::newFromKey() validates incoming keys and throws an
  InvalidArgumentException if a required key component was missing.
- It does so by eagerly destructuring the return value of explode(),
  which causes a PHP Notice for invalid inputs as the expected offsets
  won't exist then.

What:

- Check the count of key parts before destructuring.
- Add unit tests.

Bug: T385567
Change-Id: I1d936ae038f85ffa2e5d1d3d8a75fdc75e4c8ef8
(cherry picked from commit eec130925c081c2da1c475f9a9ce719e6838ca51)

includes/edit/ParsoidRenderID.php

@@ -5,6 +5,7 @@ namespace MediaWiki\Edit;
 use InvalidArgumentException;
 use MediaWiki\Parser\ParserOutput;
 use Stringable;
+use function count;
 
 /**
  * Represents the identity of a specific rendering of a specific revision
@@ -37,12 +38,14 @@ class ParsoidRenderID implements Stringable {
 	 *
 	 */
 	public static function newFromKey( string $key ): self {
-		[ $revisionID, $uniqueID ] = explode( '/', $key, 2 );
+		$parts = explode( '/', $key, 2 );
 
-		if ( $revisionID === null || $uniqueID === null ) {
+		if ( count( $parts ) < 2 ) {
 			throw new InvalidArgumentException( 'Bad key: ' . $key );
 		}
 
+		[ $revisionID, $uniqueID ] = $parts;
+
 		return new self( (int)$revisionID, $uniqueID );
 	}
 

tests/phpunit/unit/includes/edit/ParsoidRenderIdTest.php

@@ -2,6 +2,7 @@
 
 namespace MediaWiki\Tests\Unit\Edit;
 
+use InvalidArgumentException;
 use MediaWiki\Edit\ParsoidRenderID;
 use MediaWikiUnitTestCase;
 
@@ -68,4 +69,34 @@ class ParsoidRenderIdTest extends MediaWikiUnitTestCase {
 		yield [ '"1/foo"XXX' ];
 		yield [ 'XXX"1/foo"' ];
 	}
+
+	/**
+	 * @dataProvider provideNewFromKey
+	 * @covers \MediaWiki\Edit\ParsoidRenderID::newFromKey
+	 */
+	public function testNewFromKey( string $key, ParsoidRenderID $expected ): void {
+		$actual = ParsoidRenderID::newFromKey( $key );
+		$this->assertSame( $expected->getKey(), $actual->getKey() );
+	}
+
+	public static function provideNewFromKey(): iterable {
+		yield [ '1/abc', new ParsoidRenderID( 1, 'abc' ) ];
+		yield [ '2/bar', new ParsoidRenderID( 2, 'bar' ) ];
+	}
+
+	/**
+	 * @dataProvider provideBadKeys
+	 * @covers \MediaWiki\Edit\ParsoidRenderID::newFromKey
+	 */
+	public function testBadNewFromKey( $key ): void {
+		$this->expectException( InvalidArgumentException::class );
+		$this->expectExceptionMessage( "Bad key: $key" );
+
+		ParsoidRenderID::newFromKey( $key );
+	}
+
+	public static function provideBadKeys(): iterable {
+		yield [ '' ];
+		yield [ '1' ];
+	}
 }