Add support for mapping a namespace prefix onto many dirs in the autoload config

doc/04-schema.md

@@ -204,6 +204,14 @@ Example:
     }
 
 Optional, but it is highly recommended that you follow PSR-0 and use this.
+If you need to search for a same namespace prefix in multiple directories,
+you can specify them as an array as such:
+
+    {
+        "autoload": {
+            "psr-0": { "Monolog": ["src/", "lib/"] }
+        }
+    }
 
 You can use the classmap generation support to define autoloading for all libraries
 that do not follow "PSR-0". To configure this you specify all directories

res/composer-schema.json

@@ -125,7 +125,7 @@
             "properties": {
                 "psr-0": {
                     "type": "object",
-                    "description": "This is a hash of namespaces (keys) and the directories they can be found into (values) by the autoloader.",
+                    "description": "This is a hash of namespaces (keys) and the directories they can be found into (values, can be arrays of paths) by the autoloader.",
                     "additionalProperties": true
                 },
                 "classmap": {

src/Composer/Autoload/AutoloadGenerator.php

@@ -172,11 +172,12 @@ EOF;
             }
 
             foreach ($package->getAutoload() as $type => $mapping) {
-                foreach ($mapping as $namespace => $path) {
+                foreach ($mapping as $namespace => $paths) {
+                    foreach ((array) $paths as $path) {
                         $autoloads[$type][$namespace][] = empty($installPath) ? $path : $installPath.'/'.$path;
                     }
                 }
-
+            }
         }
 
         foreach ($autoloads as $type => $maps) {

tests/Composer/Test/Autoload/AutoloadGeneratorTest.php

@@ -77,7 +77,7 @@ class AutoloadGeneratorTest extends TestCase
     {
         $package = new MemoryPackage('a', '1.0', '1.0');
         $package->setAutoload(array(
-            'psr-0' => array('Main' => 'src/', 'Lala' => 'src/'),
+            'psr-0' => array('Main' => 'src/', 'Lala' => array('src/', 'lib/')),
             'classmap' => array('.composersrc/'),
         ));
 

tests/Composer/Test/Autoload/Fixtures/autoload_main.php

@@ -7,5 +7,5 @@ $baseDir = dirname($vendorDir);
 
 return array(
     'Main' => $baseDir . '/src/',
-    'Lala' => $baseDir . '/src/',
+    'Lala' => array($baseDir . '/src/', $baseDir . '/lib/'),
 );