Detect duplicate keys in composer.json, fixes #4620

composer.json

@@ -26,7 +26,7 @@
         "justinrainbow/json-schema": "^1.4.4",
         "composer/spdx-licenses": "^1.0",
         "composer/semver": "^1.0",
-        "seld/jsonlint": "^1.0",
+        "seld/jsonlint": "^1.4",
         "symfony/console": "^2.5 || ^3.0",
         "symfony/finder": "^2.2 || ^3.0",
         "symfony/process": "^2.1 || ^3.0",

composer.lock

@@ -4,8 +4,8 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#composer-lock-the-lock-file",
         "This file is @generated automatically"
     ],
-    "hash": "c88bd0dc7f99b674776d931973d3e1b7",
-    "content-hash": "e31b609879971d42d37f09bb6a526192",
+    "hash": "93e6b0b69e1d2831beb016b291320e65",
+    "content-hash": "e50c021dd9230b14ee88fe3d62c3923f",
     "packages": [
         {
             "name": "composer/semver",
@@ -246,20 +246,20 @@
         },
         {
             "name": "seld/jsonlint",
-            "version": "1.3.1",
+            "version": "1.4.0",
             "source": {
                 "type": "git",
                 "url": "https://github.com/Seldaek/jsonlint.git",
-                "reference": "863ae85c6d3ef60ca49cb12bd051c4a0648c40c4"
+                "reference": "66834d3e3566bb5798db7294619388786ae99394"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/Seldaek/jsonlint/zipball/863ae85c6d3ef60ca49cb12bd051c4a0648c40c4",
-                "reference": "863ae85c6d3ef60ca49cb12bd051c4a0648c40c4",
+                "url": "https://api.github.com/repos/Seldaek/jsonlint/zipball/66834d3e3566bb5798db7294619388786ae99394",
+                "reference": "66834d3e3566bb5798db7294619388786ae99394",
                 "shasum": ""
             },
             "require": {
-                "php": ">=5.3.0"
+                "php": "^5.3 || ^7.0"
             },
             "bin": [
                 "bin/jsonlint"
@@ -288,7 +288,7 @@
                 "parser",
                 "validator"
             ],
-            "time": "2015-01-04 21:18:15"
+            "time": "2015-11-21 02:21:41"
         },
         {
             "name": "seld/phar-utils",

src/Composer/Factory.php

@@ -25,6 +25,7 @@ use Symfony\Component\Console\Formatter\OutputFormatterStyle;
 use Composer\EventDispatcher\EventDispatcher;
 use Composer\Autoload\AutoloadGenerator;
 use Composer\Semver\VersionParser;
+use Seld\JsonLint\JsonParser;
 
 /**
  * Creates a configured instance of composer.
@@ -219,6 +220,14 @@ class Factory
             }
 
             $file->validateSchema(JsonFile::LAX_SCHEMA);
+            $jsonParser = new JsonParser;
+            try {
+                $jsonParser->parse(file_get_contents($localConfig), JsonParser::DETECT_KEY_CONFLICTS);
+            } catch (\Seld\JsonLint\DuplicateKeyException $e) {
+                $details = $e->getDetails();
+                $io->writeError('<warning>Key '.$details['key'].' is a duplicate in '.$localConfig.' at line '.$details['line'].'</warning>');
+            }
+
             $localConfig = $file->read();
         }