parse empty sequence elements as null

Author: xabbuh

Inline.php

@@ -355,11 +355,18 @@ private static function parseSequence(string $sequence, int $flags, int &$i = 0,
         ++$i;
 
         // [foo, bar, ...]
+        $lastToken = null;
         while ($i < $len) {
             if (']' === $sequence[$i]) {
                 return $output;
             }
             if (',' === $sequence[$i] || ' ' === $sequence[$i]) {
+                if (',' === $sequence[$i] && (null === $lastToken || 'separator' === $lastToken)) {
+                    $output[] = null;
+                } elseif (',' === $sequence[$i]) {
+                    $lastToken = 'separator';
+                }
+
                 ++$i;
 
                 continue;
@@ -403,6 +410,7 @@ private static function parseSequence(string $sequence, int $flags, int &$i = 0,
 
             $output[] = $value;
 
+            $lastToken = 'value';
             ++$i;
         }
 

Tests/InlineTest.php

@@ -1004,4 +1004,11 @@ public function testParseQuotedReferenceLikeStringsInSequence()
 
         $this->assertSame(['&foo', '&bar', '&baz'], Inline::parse($yaml));
     }
+
+    public function testParseSequenceWithEmptyElement()
+    {
+        $this->assertSame(['foo', null, 'bar'], Inline::parse('[foo, , bar]'));
+        $this->assertSame([null, 'foo', 'bar'], Inline::parse('[, foo, bar]'));
+        $this->assertSame(['foo', 'bar'], Inline::parse('[foo, bar, ]'));
+    }
 }