Detect missing backslashes further along in the string, fixes #54

Author: Seldaek

src/Seld/JsonLint/JsonParser.php

@@ -202,9 +202,9 @@ public function parse($input, $flags = 0)
                         $message = "Invalid string";
                         if ("'" === substr($this->lexer->match, 0, 1)) {
                             $message .= ", it appears you used single quotes instead of double quotes";
-                        } elseif (preg_match('{".+?(\\\\[^"bfnrt/\\\\u])}', $this->lexer->getUpcomingInput(), $match)) {
+                        } elseif (preg_match('{".+?(\\\\[^"bfnrt/\\\\u](...)?)}', $this->lexer->getFullUpcomingInput(), $match)) {
                             $message .= ", it appears you have an unescaped backslash at: ".$match[1];
-                        } elseif (preg_match('{"(?:[^"]+|\\\\")*$}m', $this->lexer->getUpcomingInput())) {
+                        } elseif (preg_match('{"(?:[^"]+|\\\\")*$}m', $this->lexer->getFullUpcomingInput())) {
                             $message .= ", it appears you forgot to terminate a string, or attempted to write a multiline string which is invalid";
                         }
                     }

src/Seld/JsonLint/Lexer.php

@@ -104,6 +104,20 @@ public function getUpcomingInput()
         return substr($next, 0, 20) . (\strlen($next) > 20 ? '...' : '');
     }
 
+    public function getFullUpcomingInput()
+    {
+        $next = $this->match;
+        if (substr($next, 0, 1) === '"' && substr_count($next, '"') === 1) {
+            $len = \strlen($this->input);
+            $strEnd = min(strpos($this->input, '"', $this->offset + 1) ?: $len, strpos($this->input, "\n", $this->offset + 1) ?: $len);
+            $next .= substr($this->input, $this->offset, $strEnd - $this->offset);
+        } elseif (\strlen($next) < 20) {
+            $next .= substr($this->input, $this->offset, 20 - \strlen($next));
+        }
+
+        return $next;
+    }
+
     protected function parseError($str, $hash)
     {
         throw new \Exception($str);

tests/JsonParserTest.php

@@ -99,6 +99,44 @@ public function testErrorOnUnescapedBackslash()
         }
     }
 
+    public function testErrorOnLongUnescapedBackslash()
+    {
+        $parser = new JsonParser();
+        try {
+            $parser->parse('{
+    "#3026386-26 - Drush fatal error after upgrading to 8.6.6, 8.5.9, or 7.62: PHP Fatal error: Uncaught TYPO3\PharStreamWrapper\Exception": "https://www.drupal.org/files/issues/2019-01-16/d8-3026386-26.patch"
+}');
+            $this->fail('Invalid unescaped string should be detected');
+        } catch (ParsingException $e) {
+            $expected = <<<'EXPECTED'
+Parse error on line 1:
+{    "#3026386-26 - Drush
+----^
+Invalid string, it appears you have an unescaped backslash at: \Phar
+EXPECTED;
+            $this->assertEquals($expected, $e->getMessage());
+        }
+    }
+
+    public function testErrorOnLongUnescapedBackslash2()
+    {
+        $parser = new JsonParser();
+        try {
+            $parser->parse('{
+    "#3026386-26 - Drush fatal error after upgrading to 8.6.6, 8.5.9, or 7.62: PHP Fatal error": "https://www.drupal.org/files/issues/201\9-01-16/d8-3026386-26.patch
+}');
+            $this->fail('Invalid unescaped string should be detected');
+        } catch (ParsingException $e) {
+            $expected = <<<'EXPECTED'
+Parse error on line 2:
+...: PHP Fatal error": "https://www.drupal.
+----------------------^
+Invalid string, it appears you have an unescaped backslash at: \9-01
+EXPECTED;
+            $this->assertEquals($expected, $e->getMessage());
+        }
+    }
+
     public function testErrorOnUnterminatedString()
     {
         $parser = new JsonParser();