matcher fails when trying to use empty string as a pattern (#119)

Author: jkobus

Diff for: src/Parser.php

@@ -46,6 +46,10 @@ public function parse(string $pattern) : Pattern\TypePattern
 
     public function getAST(string $pattern) : AST\Pattern
     {
+        if($pattern === '') {
+            return new AST\Pattern(new AST\Type(''));
+        }
+
         $this->lexer->setInput($pattern);
         return $this->getPattern();
     }

Diff for: tests/MatcherTest.php

@@ -422,4 +422,32 @@ public static function nullExamples()
             ],
         ];
     }
+
+    public static function emptyPatternString()
+    {
+        return [
+            [
+                '', '', true,
+                '123', '', false,
+                ' ', '', false,
+                null, '', false,
+                1, '', false,
+                0, '', false,
+                '{"name": "123"}', '{"name": ""}', false,
+                '{"name": ""}', '{"name": ""}', true,
+            ],
+        ];
+    }
+
+    /**
+     * @dataProvider emptyPatternString
+     */
+    public function test_empty_pattern_in_the_json($value, $pattern, $expectedResult)
+    {
+        $factory = new SimpleFactory();
+        $matcher = $factory->createMatcher();
+
+        $match = $matcher->match($value, $pattern);
+        $this->assertSame($expectedResult, $match);
+    }
 }