Added support for an empty comment

Author: waltertamboer

src/Lexer/AbstractLexer.php

@@ -97,7 +97,7 @@ public function getNextToken(): ?TokenInterface
         }
 
         // Match a comment:
-        if (preg_match('/^\s*\{(.+?)\}\s*/s', $this->buffer, $matches)) {
+        if (preg_match('/^\s*\{(.*?)\}\s*/s', $this->buffer, $matches)) {
             $this->buffer = substr($this->buffer, strlen($matches[0]));
             return new Comment($matches[1]);
         }

tests/Lexer/StringLexerTest.php

@@ -9,6 +9,7 @@
 
 namespace ChessZebra\PortableGameNotation\Lexer;
 
+use ChessZebra\PortableGameNotation\Token\Comment;
 use ChessZebra\PortableGameNotation\Token\MoveNumber;
 use PHPUnit\Framework\TestCase;
 
@@ -27,4 +28,34 @@ public function testConstructor()
         // Assert
         static::assertInstanceOf(MoveNumber::class, $result);
     }
+
+    public function testEmptyComment()
+    {
+        // Arrange
+        $buffer = '{}';
+
+        $lexer = new StringLexer($buffer);
+
+        // Act
+        $result = $lexer->peekNextToken();
+
+        // Assert
+        static::assertInstanceOf(Comment::class, $result);
+        static::assertEquals('', $result->getComment());
+    }
+
+    public function testPopulatedComment()
+    {
+        // Arrange
+        $buffer = '{ hello world }';
+
+        $lexer = new StringLexer($buffer);
+
+        // Act
+        $result = $lexer->peekNextToken();
+
+        // Assert
+        static::assertInstanceOf(Comment::class, $result);
+        static::assertEquals(' hello world ', $result->getComment());
+    }
 }