Avoid leaking more than one character when showing position of a file…

… that is clearly not json

src/Seld/JsonLint/Lexer.php

@@ -140,6 +140,10 @@ public function setInput($input)
      */
     public function showPosition()
     {
+        if ($this->yylineno === 0 && $this->offset === 1 && $this->match !== '{') {
+            return $this->match.'...' . "\n^";
+        }
+
         $pre = str_replace("\n", '', $this->getPastInput());
         $c = str_repeat('-', max(0, \strlen($pre) - 1)); // new Array(pre.length + 1).join("-");
 

tests/JsonParserTest.php

@@ -177,6 +177,17 @@ public function testErrorAtBeginning()
         }
     }
 
+    public function testAvoidLeakingInfoForInvalidFiles()
+    {
+        $parser = new JsonParser();
+        try {
+            $parser->parse('ABCD');
+            $this->fail('Empty string should be invalid');
+        } catch (ParsingException $e) {
+            $this->assertContains("Parse error on line 1:\nA...\n^", $e->getMessage());
+        }
+    }
+
     public function testParsesMultiInARow()
     {
         $parser = new JsonParser();