convert empty CSV header names into numeric keys

Author: xabbuh

src/Symfony/Component/Serializer/Encoder/CsvEncoder.php

@@ -181,18 +181,24 @@ public function decode(string $data, string $format, array $context = [])
                 $depth = $headerCount[$i];
                 $arr = &$item;
                 for ($j = 0; $j < $depth; ++$j) {
+                    $headerName = $headers[$i][$j];
+
+                    if ('' === $headerName) {
+                        $headerName = $i;
+                    }
+
                     // Handle nested arrays
                     if ($j === ($depth - 1)) {
-                        $arr[$headers[$i][$j]] = $cols[$i];
+                        $arr[$headerName] = $cols[$i];
 
                         continue;
                     }
 
-                    if (!isset($arr[$headers[$i][$j]])) {
-                        $arr[$headers[$i][$j]] = [];
+                    if (!isset($arr[$headerName])) {
+                        $arr[$headerName] = [];
                     }
 
-                    $arr = &$arr[$headers[$i][$j]];
+                    $arr = &$arr[$headerName];
                 }
             }
 

src/Symfony/Component/Serializer/Tests/Encoder/CsvEncoderTest.php

@@ -218,7 +218,13 @@ public function testDecodeEmptyData()
     {
         $data = $this->encoder->decode("\n\n", 'csv');
 
-        $this->assertSame([['' => null]], $data);
+        $this->assertSame([[0 => null]], $data);
+    }
+
+    public function testMultipleEmptyHeaderNamesWithSeparator()
+    {
+        $this->encoder->decode(',.
+,', 'csv');
     }
 
     public function testEncodeVariableStructure()