Add a composer-plugin-api platform package and plugins must require it

src/Composer/Plugin/PluginInterface.php

@@ -22,6 +22,13 @@ use Composer\IO\IOInterface;
  */
 interface PluginInterface
 {
+    /**
+     * Version number of the fake composer-plugin-api package
+     *
+     * @var string
+     */
+    const PLUGIN_API_VERSION = '1.0.0';
+
     /**
      * Apply plugin modifications to composer
      *

src/Composer/Plugin/PluginManager.php

@@ -16,9 +16,11 @@ use Composer\Composer;
 use Composer\EventDispatcher\EventSubscriberInterface;
 use Composer\IO\IOInterface;
 use Composer\Package\Package;
+use Composer\Package\Version\VersionParser;
 use Composer\Repository\RepositoryInterface;
 use Composer\Package\PackageInterface;
 use Composer\Package\Link;
+use Composer\Package\LinkConstraint\VersionConstraint;
 use Composer\DependencyResolver\Pool;
 
 /**
@@ -31,6 +33,7 @@ class PluginManager
     protected $composer;
     protected $io;
     protected $globalRepository;
+    protected $versionParser;
 
     protected $plugins = array();
 
@@ -46,6 +49,7 @@ class PluginManager
         $this->composer = $composer;
         $this->io = $io;
         $this->globalRepository = $globalRepository;
+        $this->versionParser = new VersionParser();
     }
 
     /**
@@ -92,6 +96,25 @@ class PluginManager
     {
         foreach ($repo->getPackages() as $package) {
             if ('composer-plugin' === $package->getType() || 'composer-installer' === $package->getType()) {
+                $requiresComposer = null;
+                foreach ($package->getRequires() as $link) {
+                    if ($link->getTarget() == 'composer-plugin-api') {
+                        $requiresComposer = $link->getConstraint();
+                    }
+                }
+
+                if (!$requiresComposer) {
+                    throw new \RuntimeException("Plugin ".$package->getName()." is missing a require statement for a version of the composer-plugin-api package.");
+                }
+
+                if (!$requiresComposer->matches(new VersionConstraint('==', $this->versionParser->normalize(PluginInterface::PLUGIN_API_VERSION)))) {
+                    $this->io->write("<warning>The plugin ".$package->getName()." requires a version of composer-plugin-api that does not match your composer installation. You may need to run composer update with the '--no-plugins' option.</warning>");
+                }
+
+                $this->registerPackage($package);
+            }
+            // Backward compatability
+            if ('composer-installer' === $package->getType()) {
                 $this->registerPackage($package);
             }
         }

src/Composer/Repository/PlatformRepository.php

@@ -14,6 +14,7 @@ namespace Composer\Repository;
 
 use Composer\Package\CompletePackage;
 use Composer\Package\Version\VersionParser;
+use Composer\Plugin\PluginInterface;
 
 /**
  * @author Jordi Boggiano <j.boggiano@seld.be>
@@ -28,6 +29,12 @@ class PlatformRepository extends ArrayRepository
 
         $versionParser = new VersionParser();
 
+        $prettyVersion = PluginInterface::PLUGIN_API_VERSION;
+        $version = $versionParser->normalize($prettyVersion);
+        $composerPluginApi = new CompletePackage('composer-plugin-api', $version, $prettyVersion);
+        $composerPluginApi->setDescription('The Composer Plugin API');
+        parent::addPackage($composerPluginApi);
+
         try {
             $prettyVersion = PHP_VERSION;
             $version = $versionParser->normalize($prettyVersion);
@@ -36,6 +43,7 @@ class PlatformRepository extends ArrayRepository
             $version = $versionParser->normalize($prettyVersion);
         }
 
+
         $php = new CompletePackage('php', $version, $prettyVersion);
         $php->setDescription('The PHP interpreter');
         parent::addPackage($php);