From 1a9de17a88576702c1403758f72b119e80848217 Mon Sep 17 00:00:00 2001
From: Jordi Boggiano <j.boggiano@seld.be>
Date: Sun, 2 Oct 2011 21:14:00 +0200
Subject: [PATCH] Detect and report common mistakes in json syntax, refs #36

---
 src/Composer/Json/JsonFile.php | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/Composer/Json/JsonFile.php b/src/Composer/Json/JsonFile.php
index d1396ca7d..060ce25de 100644
--- a/src/Composer/Json/JsonFile.php
+++ b/src/Composer/Json/JsonFile.php
@@ -107,6 +107,11 @@ class JsonFile
                 break;
             case JSON_ERROR_SYNTAX:
                 $msg = 'Syntax error';
+                if (preg_match('#["}\]]\s*(,)\s*\}#', $json, $match, PREG_OFFSET_CAPTURE)) {
+                    $msg .= ', extra comma on line '.(substr_count(substr($json, 0, $match[1][1]), "\n")+1);
+                } elseif (preg_match('#(\'.+?\' *:|: *\'.+?\')#', $json, $match, PREG_OFFSET_CAPTURE)) {
+                    $msg .= ', use double quotes (") instead of single quotes (\') on line '.(substr_count(substr($json, 0, $match[1][1]), "\n")+1);
+                }
                 break;
             case JSON_ERROR_UTF8:
                 $msg = 'Malformed UTF-8 characters, possibly incorrectly encoded';