Treat empty month and year strings as null

Signed-off-by: ramchale <[email protected]>

src/MonthSelect.php

@@ -35,16 +35,26 @@ public function __invoke(mixed $value): mixed
         return $this->filter($value);
     }
 
+    /**
+     * Returns the result of filtering $value
+     *
+     * @template T
+     * @param T $value
+     * @return string|null|T
+     */
     public function filter(mixed $value): mixed
     {
         if (! is_array($value)) {
             return $value;
         }
 
-        /** @var mixed $month */
         $month = $value['month'] ?? null;
-        /** @var mixed $year */
+        /** @var mixed $month */
+        $month = $month === '' ? null : $month;
+
         $year = $value['year'] ?? null;
+        /** @var mixed $year */
+        $year = $year === '' ? null : $year;
 
         if ($this->returnNullIfAnyFieldEmpty && ($month === null || $year === null)) {
             return null;
@@ -55,7 +65,7 @@ public function filter(mixed $value): mixed
         }
 
         if (! $this->isParsableAsDateValue($month, 1, 12) || ! $this->isParsableAsDateValue($year, 0, 9999)) {
-            /** @psalm-suppress InvalidReturnStatement */
+            /** @psalm-var T */
             return $value;
         }
 

test/MonthSelectTest.php

@@ -32,6 +32,7 @@ public static function provideFilter(): array
             [['null_on_empty' => true], ['year' => null], null],
             [['null_on_all_empty' => true], ['year' => null, 'month' => null], null],
             [['null_on_all_empty' => true], [], null],
+            [['null_on_all_empty' => true], ['year' => '', 'month' => ''], null],
         ];
     }