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)

1 files changed, 5 insertions, 2 deletions

diff --git a/includes/edit/ParsoidRenderID.php b/includes/edit/ParsoidRenderID.php
index 005da7b305c8..fc82c5a6d1a4 100644
--- a/includes/edit/ParsoidRenderID.php
+++ b/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 );
 	}