composer/Composer.php

+<?php
+
+namespace Drupal\Composer;
+
+use Composer\Composer as ComposerApp;
+use Composer\Script\Event;
+use Composer\Semver\Comparator;
+use Composer\Semver\VersionParser;
+use Drupal\Composer\Generator\ComponentGenerator;
+use Drupal\Composer\Generator\PackageGenerator;
+use Symfony\Component\Finder\Finder;
+
+/**
+ * Provides static functions for composer script events.
+ *
+ * See also core/lib/Drupal/Composer/Composer.php, which contains similar
+ * scripts needed by projects that include drupal/core. Scripts that are only
+ * needed by drupal/drupal go here.
+ *
+ * @see https://getcomposer.org/doc/articles/scripts.md
+ */
+class Composer {
+
+  /**
+   * Update metapackages whenever composer.lock is updated.
+   *
+   * @param \Composer\Script\Event $event
+   *   The Composer event.
+   */
+  public static function generateMetapackages(Event $event): void {
+    $generator = new PackageGenerator();
+    $generator->generate($event->getIO(), getcwd());
+  }
+
+  /**
+   * Update component packages whenever composer.lock is updated.
+   *
+   * @param \Composer\Script\Event $event
+   *   The Composer event.
+   */
+  public static function generateComponentPackages(Event $event): void {
+    $generator = new ComponentGenerator();
+    $generator->generate($event, getcwd());
+  }
+
+  /**
+   * Set the version of Drupal; used in release process and by the test suite.
+   *
+   * @param string $root
+   *   Path to root of drupal/drupal repository.
+   * @param string $version
+   *   Semver version to set Drupal's version to.
+   *
+   * @throws \UnexpectedValueException
+   */
+  public static function setDrupalVersion(string $root, string $version): void {
+    // We use VersionParser::normalize to validate that $version is valid.
+    // It will throw an exception if it is not.
+    $versionParser = new VersionParser();
+    $versionParser->normalize($version);
+
+    // Rewrite Drupal.php with the provided version string.
+    $drupal_static_path = "$root/core/lib/Drupal.php";
+    $drupal_static_source = file_get_contents($drupal_static_path);
+    $drupal_static_source = preg_replace('#const VERSION = [^;]*#', "const VERSION = '$version'", $drupal_static_source);
+    file_put_contents($drupal_static_path, $drupal_static_source);
+
+    // Update the template project stability to match the version we set.
+    static::setTemplateProjectStability($root, $version);
+  }
+
+  /**
+   * Set the stability of the template projects to match the Drupal version.
+   *
+   * @param string $root
+   *   Path to root of drupal/drupal repository.
+   * @param string $version
+   *   Semver version that Drupal was set to.
+   */
+  protected static function setTemplateProjectStability(string $root, string $version): void {
+    $stability = VersionParser::parseStability($version);
+
+    $templateProjectPaths = static::composerSubprojectPaths($root, 'Template');
+    foreach ($templateProjectPaths as $path) {
+      $dir = dirname($path);
+      exec("composer --working-dir=$dir config minimum-stability $stability", $output, $status);
+      if ($status) {
+        throw new \Exception('Could not set minimum-stability for template project ' . basename($dir));
+      }
+    }
+  }
+
+  /**
+   * Ensure that the minimum required version of Composer is running.
+   *
+   * Throw an exception if Composer is too old.
+   */
+  public static function ensureComposerVersion(): void {
+    $composerVersion = method_exists(ComposerApp::class, 'getVersion') ?
+      ComposerApp::getVersion() : ComposerApp::VERSION;
+    if (Comparator::lessThan($composerVersion, '2.3.6')) {
+      throw new \RuntimeException("Drupal core development requires Composer 2.3.6, but Composer $composerVersion is installed. Run 'composer self-update'.");
+    }
+  }
+
+  /**
+   * Return the branch name the current Drupal version is associated with.
+   *
+   * @return string
+   *   A branch name, e.g. 8.9.x or 9.0.x.
+   */
+  public static function drupalVersionBranch(): string {
+    return preg_replace('#\.[0-9]+-dev#', '.x-dev', \Drupal::VERSION);
+  }
+
+  /**
+   * Return the list of subprojects of a given type.
+   *
+   * @param string $root
+   *   Path to root of drupal/drupal repository.
+   * @param string $subprojectType
+   *   Type of subproject - one of Metapackage, Plugin, or Template.
+   *
+   * @return \Symfony\Component\Finder\Finder
+   *   A Finder object.
+   */
+  public static function composerSubprojectPaths(string $root, string $subprojectType): Finder {
+    return Finder::create()
+      ->files()
+      ->name('composer.json')
+      ->in("$root/composer/$subprojectType");
+  }
+
+}

composer/Generator/Builder/DrupalCoreRecommendedBuilder.php

+<?php
+
+namespace Drupal\Composer\Generator\Builder;
+
+use Drupal\Composer\Composer;
+
+/**
+ * Builder to produce metapackage for drupal/core-recommended.
+ */
+class DrupalCoreRecommendedBuilder extends DrupalPackageBuilder {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPath() {
+    return 'CoreRecommended';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPackage() {
+
+    $composer = $this->initialPackageMetadata();
+
+    // Pull up the composer lock data.
+    $composerLockData = $this->drupalCoreInfo->composerLock();
+    if (!isset($composerLockData['packages'])) {
+      return $composer;
+    }
+
+    // Make a list of packages we do not want to put in the 'require' section.
+    $remove_list = [
+      'drupal/core',
+      'wikimedia/composer-merge-plugin',
+      'composer/installers',
+      // This package contains no code other than interfaces, so allow sites
+      // to use any compatible version without needing to switch off of
+      // drupal/core-recommended.
+      'psr/http-message',
+    ];
+
+    // Copy the 'packages' section from the Composer lock into our 'require'
+    // section. There is also a 'packages-dev' section, but we do not need
+    // to pin 'require-dev' versions, as 'require-dev' dependencies are never
+    // included from subprojects. Use 'drupal/core-dev' to get Drupal's
+    // dev dependencies.
+    foreach ($composerLockData['packages'] as $package) {
+      // If there is no 'source' record, then this is a path repository
+      // or something else that we do not want to include.
+      if (isset($package['source']) && !in_array($package['name'], $remove_list)) {
+        $composer['require'][$package['name']] = '~' . $package['version'];
+      }
+    }
+    return $composer;
+  }
+
+  /**
+   * Returns the initial package metadata that describes the metapackage.
+   *
+   * @return array
+   *   The initial package metadata.
+   */
+  protected function initialPackageMetadata() {
+    return [
+      "name" => "drupal/core-recommended",
+      "type" => "metapackage",
+      "description" => "Core and its dependencies with known-compatible minor versions. Require this project INSTEAD OF drupal/core.",
+      "license" => "GPL-2.0-or-later",
+      "conflict" => [
+        "webflo/drupal-core-strict" => "*",
+      ],
+      "require" => [
+        "drupal/core" => Composer::drupalVersionBranch(),
+      ],
+    ];
+  }
+
+}

composer/Generator/Builder/DrupalDevDependenciesBuilder.php

+<?php
+
+namespace Drupal\Composer\Generator\Builder;
+
+/**
+ * Builder to produce metapackage for drupal/core-dev.
+ */
+class DrupalDevDependenciesBuilder extends DrupalPackageBuilder {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPath() {
+    return 'DevDependencies';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPackage() {
+
+    $composer = $this->initialPackageMetadata();
+
+    // Put everything from Drupal's "require-dev" into our "require" section.
+    $composer['require'] = $this->drupalCoreInfo->getRequireDev();
+
+    // Sort our required packages by key.
+    ksort($composer['require']);
+
+    return $composer;
+  }
+
+  /**
+   * Returns the initial package metadata that describes the metapackage.
+   *
+   * @return array
+   *   The initial package metadata.
+   */
+  protected function initialPackageMetadata() {
+    return [
+      "name" => "drupal/core-dev",
+      "type" => "metapackage",
+      "description" => "require-dev dependencies from drupal/drupal; use in addition to drupal/core-recommended to run tests from drupal/core.",
+      "license" => "GPL-2.0-or-later",
+      "conflict" => [
+        "webflo/drupal-core-require-dev" => "*",
+      ],
+    ];
+  }
+
+}

composer/Generator/Builder/DrupalPackageBuilder.php

+<?php
+
+namespace Drupal\Composer\Generator\Builder;
+
+use Drupal\Composer\Generator\BuilderInterface;
+use Drupal\Composer\Generator\Util\DrupalCoreComposer;
+
+/**
+ * Base class that includes helpful utility routine for Drupal builder classes.
+ */
+abstract class DrupalPackageBuilder implements BuilderInterface {
+
+  /**
+   * Information about composer.json, composer.lock etc. in current release.
+   *
+   * @var \Drupal\Composer\Generator\Util\DrupalCoreComposer
+   */
+  protected $drupalCoreInfo;
+
+  /**
+   * DrupalPackageBuilder constructor.
+   *
+   * @param \Drupal\Composer\Generator\Util\DrupalCoreComposer $drupalCoreInfo
+   *   Information about composer.json and composer.lock from current release.
+   */
+  public function __construct(DrupalCoreComposer $drupalCoreInfo) {
+    $this->drupalCoreInfo = $drupalCoreInfo;
+  }
+
+}

composer/Generator/Builder/DrupalPinnedDevDependenciesBuilder.php

+<?php
+
+namespace Drupal\Composer\Generator\Builder;
+
+use Drupal\Composer\Composer;
+
+/**
+ * Builder to produce metapackage for drupal/core-dev-pinned.
+ */
+class DrupalPinnedDevDependenciesBuilder extends DrupalPackageBuilder {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPath() {
+    return 'PinnedDevDependencies';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getPackage() {
+
+    $composer = $this->initialPackageMetadata();
+
+    // Pull the exact versions of the dependencies from the composer.lock
+    // file and use it to build our 'require' section.
+    $composerLockData = $this->drupalCoreInfo->composerLock();
+
+    if (isset($composerLockData['packages-dev'])) {
+      foreach ($composerLockData['packages-dev'] as $package) {
+        $composer['require'][$package['name']] = $package['version'];
+      }
+    }
+    return $composer;
+  }
+
+  /**
+   * Returns the initial package metadata that describes the metapackage.
+   *
+   * @return array
+   *   The initial package metadata.
+   */
+  protected function initialPackageMetadata() {
+    return [
+      "name" => "drupal/core-dev-pinned",
+      "type" => "metapackage",
+      "description" => "Pinned require-dev dependencies from drupal/drupal; use in addition to drupal/core-recommended to run tests from drupal/core.",
+      "license" => "GPL-2.0-or-later",
+      "conflict" => [
+        "webflo/drupal-core-require-dev" => "*",
+      ],
+      "require" => [
+        "drupal/core" => Composer::drupalVersionBranch(),
+      ],
+    ];
+  }
+
+}

composer/Generator/BuilderInterface.php

+<?php
+
+namespace Drupal\Composer\Generator;
+
+use Drupal\Composer\Generator\Util\DrupalCoreComposer;
+
+/**
+ * Produce the output for a metapackage.
+ *
+ * BuilderInterface provides an interface for builder classes which are
+ * called by the PackageGenerator in order to produce a derived metapackage from
+ * the provided source package.
+ *
+ * See the README.txt file in composer/Metapackage for a description of what
+ * a metapackage is, and an explanation of the metapackages produced by the
+ * generator.
+ */
+interface BuilderInterface {
+
+  /**
+   * BuilderInterface constructor.
+   *
+   * @param \Drupal\Composer\Generator\Util\DrupalCoreComposer $drupalCoreInfo
+   *   Information about the composer.json, composer.lock, and repository path.
+   */
+  public function __construct(DrupalCoreComposer $drupalCoreInfo);
+
+  /**
+   * Return the path to where the metapackage should be written.
+   *
+   * @return string
+   *   Path to the metapackage.
+   */
+  public function getPath();
+
+  /**
+   * Generate the Composer.json data for the current tag or branch.
+   *
+   * @return array
+   *   Composer json data.
+   */
+  public function getPackage();
+
+}

composer/Generator/ComponentGenerator.php

+<?php
+
+namespace Drupal\Composer\Generator;
+
+use Composer\IO\IOInterface;
+use Composer\Semver\VersionParser;
+use Composer\Script\Event;
+use Composer\Util\Filesystem;
+use Drupal\Composer\Composer;
+use Drupal\Composer\Generator\Util\DrupalCoreComposer;
+use Drupal\Composer\Util\SemanticVersion;
+use Symfony\Component\Finder\Finder;
+
+/**
+ * Reconciles Drupal component dependencies with core.
+ */
+class ComponentGenerator {
+
+  /**
+   * Relative path from Drupal root to the component directory.
+   *
+   * @var string
+   */
+  protected static $relativeComponentPath = 'core/lib/Drupal/Component';
+
+  /**
+   * Full path to the component directory.
+   *
+   * @var string
+   */
+  protected $componentBaseDir;
+
+  /**
+   * Data from drupal/drupal's composer.json file.
+   *
+   * @var \Drupal\Composer\Generator\Util\DrupalCoreComposer
+   */
+  protected $drupalProjectInfo;
+
+  /**
+   * Data from drupal/core's composer.json file.
+   *
+   * @var \Drupal\Composer\Generator\Util\DrupalCoreComposer
+   */
+  protected $drupalCoreInfo;
+
+  /**
+   * ComponentGenerator constructor.
+   */
+  public function __construct() {
+    $this->componentBaseDir = dirname(__DIR__, 2) . '/' . static::$relativeComponentPath;
+  }
+
+  /**
+   * Find all the composer.json files for components.
+   *
+   * @return \Symfony\Component\Finder\Finder
+   *   A Finder object with all the composer.json files for components.
+   */
+  public function getComponentPathsFinder(): Finder {
+    $composer_json_finder = new Finder();
+    $composer_json_finder->name('composer.json')
+      ->in($this->componentBaseDir)
+      ->ignoreUnreadableDirs()
+      ->depth(1);
+    return $composer_json_finder;
+  }
+
+  /**
+   * Reconcile Drupal's components whenever composer.lock is updated.
+   *
+   * @param \Composer\Script\Event $event
+   *   The Composer event.
+   * @param string $base_dir
+   *   Directory where drupal/drupal repository is located.
+   */
+  public function generate(Event $event, string $base_dir): void {
+    $io = $event->getIO();
+    // General information from drupal/drupal and drupal/core composer.json
+    // and composer.lock files.
+    $this->drupalProjectInfo = DrupalCoreComposer::createFromPath($base_dir);
+    $this->drupalCoreInfo = DrupalCoreComposer::createFromPath($base_dir . '/core');
+
+    $changed = FALSE;
+    /** @var \Symfony\Component\Finder\SplFileInfo $component_composer_json */
+    foreach ($this->getComponentPathsFinder()->getIterator() as $component_composer_json) {
+      $changed |= $this->generateComponentPackage($event, $component_composer_json->getRelativePathname());
+    }
+
+    // Remind the user not to miss files in a patch.
+    if ($changed) {
+      $io->write("If you make a patch, ensure that the files above are included.");
+    }
+  }
+
+  /**
+   * Generate the component JSON files.
+   *
+   * @param \Composer\Script\Event $event
+   *   The Composer event.
+   * @param string $component_pathname
+   *   Relative path to the composer.json file for a component.
+   *
+   * @return bool
+   *   TRUE if the generated component package is different from what is on
+   *   disk.
+   */
+  protected function generateComponentPackage(Event $event, string $component_pathname): bool {
+    $io = $event->getIO();
+    $composer_json_path = $this->componentBaseDir . '/' . $component_pathname;
+    $original_composer_json = file_exists($composer_json_path) ? file_get_contents($composer_json_path) : '';
+
+    // Modify the original data.
+    $composer_json_data = $this->getPackage($io, $original_composer_json);
+    $updated_composer_json = static::encode($composer_json_data);
+
+    // Exit early if nothing changed.
+    if (trim($original_composer_json, " \t\r\0\x0B") === trim($updated_composer_json, " \t\r\0\x0B")) {
+      return FALSE;
+    }
+
+    // Warn the user that a component file has been updated.
+    $display_path = static::$relativeComponentPath . '/' . $component_pathname;
+    $io->write("Updated component file <info>$display_path</info>.");
+
+    // Write the composer.json file back to disk.
+    $fs = new Filesystem();
+    $fs->ensureDirectoryExists(dirname($composer_json_path));
+    file_put_contents($composer_json_path, $updated_composer_json);
+
+    return TRUE;
+  }
+
+  /**
+   * Reconcile component dependencies with core.
+   *
+   * @param \Composer\IO\IOInterface $io
+   *   IO object for messages to the user.
+   * @param string $original_json
+   *   Contents of the component's composer.json file.
+   *
+   * @return array
+   *   Structured data to be turned back into JSON.
+   */
+  protected function getPackage(IOInterface $io, string $original_json): array {
+    $original_data = json_decode($original_json, TRUE);
+    $package_data = array_merge($original_data, $this->initialPackageMetadata());
+
+    $core_info = $this->drupalCoreInfo->rootComposerJson();
+
+    $stability = VersionParser::parseStability(\Drupal::VERSION);
+
+    // List of packages which we didn't find in either core requirement.
+    $not_in_core = [];
+
+    // Traverse required packages.
+    foreach (array_keys($original_data['require'] ?? []) as $package_name) {
+      // Reconcile locked constraints from drupal/drupal. We might have a locked
+      // version of a dependency that's not present in drupal/core.
+      if ($info = $this->drupalProjectInfo->packageLockInfo($package_name)) {
+        $package_data['require'][$package_name] = $info['version'];
+      }
+      // The package wasn't in the lock file, which means we need to tell the
+      // user. But there are some packages we want to exclude from this list.
+      elseif ($package_name !== 'php' && !str_contains($package_name, 'drupal/core-')) {
+        $not_in_core[$package_name] = $package_name;
+      }
+
+      // Reconcile looser constraints from drupal/core, and we're totally OK
+      // with over-writing the locked ones from above.
+      if ($constraint = $core_info['require'][$package_name] ?? FALSE) {
+        $package_data['require'][$package_name] = $constraint;
+      }
+
+      // Reconcile dependencies on other Drupal components, so we can set the
+      // constraint to our current version.
+      if (str_contains($package_name, 'drupal/core-')) {
+        if ($stability === 'stable') {
+          // Set the constraint to ^maj.min.
+          $package_data['require'][$package_name] = SemanticVersion::majorMinorConstraint(\Drupal::VERSION);
+        }
+        else {
+          // For non-stable releases, set the constraint to the branch version.
+          $package_data['require'][$package_name] = Composer::drupalVersionBranch();
+          // Also for non-stable releases which depend on another component,
+          // set the minimum stability. We do this so we can test build the
+          // components. Minimum-stability is otherwise ignored for packages
+          // which aren't the root package, so for any other purpose, this is
+          // unneeded.
+          $package_data['minimum-stability'] = $stability;
+        }
+      }
+    }
+    if ($not_in_core) {
+      $io->error($package_data['name'] . ' requires packages not present in drupal/drupal: ' . implode(', ', $not_in_core));
+    }
+
+    return $package_data;
+  }
+
+  /**
+   * Utility function to encode package json in a consistent way.
+   *
+   * @param array $composer_json_data
+   *   Data to encode into a json string.
+   *
+   * @return string
+   *   Encoded version of provided json data.
+   */
+  public static function encode(array $composer_json_data): string {
+    return json_encode($composer_json_data, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES) . "\n";
+  }
+
+  /**
+   * Common default metadata for all components.
+   *
+   * @return array
+   *   An array containing the common default metadata for all components.
+   */
+  protected function initialPackageMetadata(): array {
+    return [
+      'extra' => [
+        '_readme' => [
+          'This file was partially generated automatically. See: https://www.drupal.org/node/3293830',
+        ],
+      ],
+      // Always reconcile PHP version.
+      'require' => [
+        'php' => '>=' . \Drupal::MINIMUM_PHP,
+      ],
+    ];
+  }
+
+}

composer/Generator/PackageGenerator.php

+<?php
+
+namespace Drupal\Composer\Generator;
+
+use Drupal\Composer\Generator\Builder\DrupalCoreRecommendedBuilder;
+use Drupal\Composer\Generator\Builder\DrupalDevDependenciesBuilder;
+use Drupal\Composer\Generator\Builder\DrupalPinnedDevDependenciesBuilder;
+use Drupal\Composer\Generator\Util\DrupalCoreComposer;
+use Composer\Util\Filesystem;
+use Composer\IO\IOInterface;
+
+/**
+ * Generates metapackages.
+ */
+class PackageGenerator {
+
+  /**
+   * Base directory where generated projects are written.
+   *
+   * @var string
+   */
+  protected $generatedProjectBaseDir;
+
+  /**
+   * PackageGenerator constructor.
+   */
+  public function __construct() {
+    $this->generatedProjectBaseDir = dirname(__DIR__) . '/Metapackage';
+  }
+
+  /**
+   * Generate Drupal's metapackages whenever composer.lock is updated.
+   *
+   * @param \Composer\IO\IOInterface $io
+   *   Composer IO object for interacting with the user.
+   * @param string $base_dir
+   *   Directory where drupal/drupal repository is located.
+   */
+  public function generate(IOInterface $io, $base_dir) {
+    // General information from drupal/drupal and drupal/core composer.json
+    // and composer.lock files.
+    $drupalCoreInfo = DrupalCoreComposer::createFromPath($base_dir);
+
+    // Exit early if there is no composer.lock file.
+    if (empty($drupalCoreInfo->composerLock())) {
+      return;
+    }
+
+    // Run all of our available builders.
+    $builders = $this->builders();
+    $changed = FALSE;
+    foreach ($builders as $builder_class) {
+      $builder = new $builder_class($drupalCoreInfo);
+      $changed |= $this->generateMetapackage($io, $builder);
+    }
+
+    // Remind the user not to miss files in a patch.
+    if ($changed) {
+      $io->write("If you make a patch, ensure that the files above are included.");
+    }
+  }
+
+  /**
+   * Returns a list of metapackage builders.
+   *
+   * @return BuilderInterface[]
+   *   An array of BuilderInterface objects.
+   */
+  protected function builders() {
+    return [
+      DrupalCoreRecommendedBuilder::class,
+      DrupalDevDependenciesBuilder::class,
+      DrupalPinnedDevDependenciesBuilder::class,
+    ];
+  }
+
+  /**
+   * Generate one metapackage.
+   *
+   * @param \Composer\IO\IOInterface $io
+   *   Composer IO object for interacting with the user.
+   * @param BuilderInterface $builder
+   *   An object that can build a metapackage.
+   *
+   * @return bool
+   *   TRUE if the generated metapackage is different than what is on disk.
+   */
+  protected function generateMetapackage(IOInterface $io, BuilderInterface $builder) {
+
+    // Load the existing composer.json file for drupal/core-recommended
+    $relative_path = $builder->getPath() . '/composer.json';
+    $composer_json_path = $this->generatedProjectBaseDir . '/' . $relative_path;
+    $original_composer_json = file_exists($composer_json_path) ? file_get_contents($composer_json_path) : '';
+
+    // Get the composer.json file from the builder.
+    $composer_json_data = $builder->getPackage();
+    $updated_composer_json = static::encode($composer_json_data);
+
+    // Exit early if nothing changed.
+    if (trim($original_composer_json, " \t\r\0\x0B") == trim($updated_composer_json, " \t\r\0\x0B")) {
+      return FALSE;
+    }
+
+    // Warn the user that a metapackage file has been updated..
+    $io->write("Updated metapackage file <info>composer/Metapackage/$relative_path</info>.");
+
+    // Write the composer.json file back to disk
+    $fs = new Filesystem();
+    $fs->ensureDirectoryExists(dirname($composer_json_path));
+    file_put_contents($composer_json_path, $updated_composer_json);
+
+    return TRUE;
+  }
+
+  /**
+   * Utility function to encode metapackage json in a consistent way.
+   *
+   * @param array $composer_json_data
+   *   Data to encode into a json string.
+   *
+   * @return string
+   *   Encoded version of provided json data.
+   */
+  public static function encode($composer_json_data) {
+    return json_encode($composer_json_data, JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES) . "\n";
+  }
+
+}

composer/Generator/TESTING.txt

+HOW-TO: Test this Drupal composer script
+
+In order to test this script, you'll need to get the entire Drupal repo and
+run the tests there.
+
+You'll find the tests under core/tests/Drupal/Tests/Composer/Generator.
+
+You can get the full Drupal repo here:
+https://www.drupal.org/project/drupal/git-instructions
+
+You can find more information about running PHPUnit tests with Drupal here:
+https://www.drupal.org/node/2116263
+
+Each component in the Drupal\Composer\Plugin namespace has its own annotated test
+group. You can use this group to run only the tests for this component. Like
+this:
+
+$ ./vendor/bin/phpunit -c core --group Metapackage

composer/Generator/Util/DrupalCoreComposer.php

+<?php
+
+namespace Drupal\Composer\Generator\Util;
+
+/**
+ * Utilities for accessing composer.json data from drupal/drupal and drupal/core.
+ *
+ * Some data is stored in the root composer.json file, while others is found
+ * in the core/composer.json file.
+ */
+class DrupalCoreComposer {
+
+  /**
+   * Cached composer.json data.
+   *
+   * @var array
+   */
+  protected $composerJson = [];
+
+  /**
+   * Cached composer.lock data.
+   *
+   * @var array
+   */
+  protected $composerLock = [];
+
+  /**
+   * DrupalCoreComposer constructor.
+   *
+   * @param array $composerJson
+   *   The composer.json data.
+   * @param array $composerLock
+   *   The composer.lock data.
+   */
+  public function __construct(array $composerJson, array $composerLock) {
+    $this->composerJson = $composerJson;
+    $this->composerLock = $composerLock;
+  }
+
+  /**
+   * DrupalCoreComposer factory.
+   *
+   * @param string $repositoryPath
+   *   Path to a directory containing a composer.json and composer.lock files.
+   *
+   * @return static
+   *   New DrupalCoreComposer object containing composer.json and lock data.
+   */
+  public static function createFromPath(string $repositoryPath) {
+    $composerJson = static::loadJsonFromPath("$repositoryPath/composer.json");
+    $composerLock = static::loadJsonFromPath("$repositoryPath/composer.lock");
+    return new self($composerJson, $composerLock);
+  }
+
+  /**
+   * Fetch the composer data from the root drupal/drupal project.
+   *
+   * @return array
+   *   Composer json data
+   */
+  public function rootComposerJson() {
+    return $this->composerJson;
+  }
+
+  /**
+   * Fetch the composer lock data.
+   *
+   * @return array
+   *   Composer lock data
+   */
+  public function composerLock() {
+    return $this->composerLock;
+  }
+
+  /**
+   * Return the "require-dev" section from root or core composer.json file.
+   *
+   * The require-dev constraints moved from core/composer.json (8.7.x and
+   * earlier) to the root composer.json file (8.8.x and later).
+   *
+   * @return array
+   *   The contents of the "require-dev" section.
+   */
+  public function getRequireDev() {
+    $composerJsonData = $this->rootComposerJson();
+    return $composerJsonData['require-dev'] ?? [];
+  }
+
+  /**
+   * Look up the info for one package in the composer.lock file.
+   *
+   * @param string $packageName
+   *   Name of package to find, e.g. 'behat/mink-selenium2-driver'.
+   * @param bool $dev
+   *   TRUE: consider only 'packages-dev'. Default: consider only 'packages'.
+   *
+   * @return array
+   *   Package info from composer.lock.
+   */
+  public function packageLockInfo($packageName, $dev = FALSE) {
+    $packagesSection = $dev ? 'packages-dev' : 'packages';
+    foreach ($this->composerLock[$packagesSection] as $info) {
+      if ($info['name'] == $packageName) {
+        return $info;
+      }
+    }
+    return [];
+  }
+
+  /**
+   * Load json data from the specified path.
+   *
+   * @param string $path
+   *   Relative path to the json file to load.
+   *
+   * @return array
+   *   The contents of the json data for the specified file.
+   */
+  protected static function loadJsonFromPath($path) {
+    return file_exists($path) ? json_decode(file_get_contents($path), TRUE) : [];
+  }
+
+}

composer/Metapackage/CoreRecommended/composer.json

+{
+    "name": "drupal/core-recommended",
+    "type": "metapackage",
+    "description": "Core and its dependencies with known-compatible minor versions. Require this project INSTEAD OF drupal/core.",
+    "license": "GPL-2.0-or-later",
+    "conflict": {
+        "webflo/drupal-core-strict": "*"
+    },
+    "require": {
+        "drupal/core": "11.x-dev",
+        "asm89/stack-cors": "~v2.2.0",
+        "composer/semver": "~3.4.3",
+        "doctrine/annotations": "~2.0.2",
+        "doctrine/deprecations": "~1.1.3",
+        "doctrine/lexer": "~2.1.1",
+        "egulias/email-validator": "~4.0.2",
+        "guzzlehttp/guzzle": "~7.9.2",
+        "guzzlehttp/promises": "~2.0.4",
+        "guzzlehttp/psr7": "~2.7.0",
+        "masterminds/html5": "~2.9.0",
+        "mck89/peast": "~v1.16.3",
+        "pear/archive_tar": "~1.5.0",
+        "pear/console_getopt": "~v1.4.3",
+        "pear/pear-core-minimal": "~v1.10.16",
+        "pear/pear_exception": "~v1.0.2",
+        "php-tuf/composer-stager": "~v2.0.0",
+        "psr/cache": "~3.0.0",
+        "psr/container": "~2.0.2",
+        "psr/event-dispatcher": "~1.0.0",
+        "psr/http-client": "~1.0.3",
+        "psr/http-factory": "~1.1.0",
+        "psr/log": "~3.0.2",
+        "ralouphie/getallheaders": "~3.0.3",
+        "revolt/event-loop": "~v1.0.6",
+        "sebastian/diff": "~5.1.1",
+        "symfony/console": "~v7.2.0",
+        "symfony/dependency-injection": "~v7.2.0",
+        "symfony/deprecation-contracts": "~v3.5.1",
+        "symfony/error-handler": "~v7.2.0",
+        "symfony/event-dispatcher": "~v7.2.0",
+        "symfony/event-dispatcher-contracts": "~v3.5.1",
+        "symfony/filesystem": "~v7.2.0",
+        "symfony/finder": "~v7.2.0",
+        "symfony/http-foundation": "~v7.2.0",
+        "symfony/http-kernel": "~v7.2.0",
+        "symfony/mailer": "~v7.2.0",
+        "symfony/mime": "~v7.2.0",
+        "symfony/polyfill-ctype": "~v1.31.0",
+        "symfony/polyfill-iconv": "~v1.31.0",
+        "symfony/polyfill-intl-grapheme": "~v1.31.0",
+        "symfony/polyfill-intl-idn": "~v1.31.0",
+        "symfony/polyfill-intl-normalizer": "~v1.31.0",
+        "symfony/polyfill-mbstring": "~v1.31.0",
+        "symfony/process": "~v7.2.0",
+        "symfony/psr-http-message-bridge": "~v7.2.0",
+        "symfony/routing": "~v7.2.0",
+        "symfony/serializer": "~v7.2.0",
+        "symfony/service-contracts": "~v3.5.1",
+        "symfony/string": "~v7.2.0",
+        "symfony/translation-contracts": "~v3.5.1",
+        "symfony/validator": "~v7.2.0",
+        "symfony/var-dumper": "~v7.2.0",
+        "symfony/var-exporter": "~v7.2.0",
+        "symfony/yaml": "~v7.2.0",
+        "twig/twig": "~v3.19.0"
+    }
+}

composer/Metapackage/DevDependencies/composer.json

+{
+    "name": "drupal/core-dev",
+    "type": "metapackage",
+    "description": "require-dev dependencies from drupal/drupal; use in addition to drupal/core-recommended to run tests from drupal/core.",
+    "license": "GPL-2.0-or-later",
+    "conflict": {
+        "webflo/drupal-core-require-dev": "*"
+    },
+    "require": {
+        "behat/mink": "^1.11",
+        "behat/mink-browserkit-driver": "^2.2",
+        "colinodell/psr-testlogger": "^1.2",
+        "composer/composer": "^2.8.1",
+        "drupal/coder": "^8.3.10",
+        "justinrainbow/json-schema": "^5.2",
+        "lullabot/mink-selenium2-driver": "^1.7.3",
+        "lullabot/php-webdriver": "^2.0.5",
+        "mglaman/phpstan-drupal": "^1.2.11 || ^2.0",
+        "micheh/phpcs-gitlab": "^1.1",
+        "mikey179/vfsstream": "^1.6.11",
+        "open-telemetry/exporter-otlp": "^1",
+        "open-telemetry/sdk": "^1",
+        "php-http/guzzle7-adapter": "^1.0",
+        "phpspec/prophecy-phpunit": "^2",
+        "phpstan/extension-installer": "^1.4.3",
+        "phpstan/phpstan": "^1.12.4 || ^2.0.4",
+        "phpstan/phpstan-phpunit": "^1.3.16 || ^2.0.1",
+        "phpunit/phpunit": "^10.5.19",
+        "symfony/browser-kit": "^7.2",
+        "symfony/css-selector": "^7.2",
+        "symfony/dom-crawler": "^7.2",
+        "symfony/error-handler": "^7.2",
+        "symfony/lock": "^7.2",
+        "symfony/var-dumper": "^7.2"
+    }
+}

composer/Metapackage/PinnedDevDependencies/composer.json

+{
+    "name": "drupal/core-dev-pinned",
+    "type": "metapackage",
+    "description": "Pinned require-dev dependencies from drupal/drupal; use in addition to drupal/core-recommended to run tests from drupal/core.",
+    "license": "GPL-2.0-or-later",
+    "conflict": {
+        "webflo/drupal-core-require-dev": "*"
+    },
+    "require": {
+        "drupal/core": "11.x-dev",
+        "behat/mink": "v1.12.0",
+        "behat/mink-browserkit-driver": "v2.2.0",
+        "brick/math": "0.12.1",
+        "colinodell/psr-testlogger": "v1.3.0",
+        "composer/ca-bundle": "1.5.4",
+        "composer/class-map-generator": "1.5.0",
+        "composer/composer": "2.8.3",
+        "composer/metadata-minifier": "1.0.0",
+        "composer/pcre": "3.3.2",
+        "composer/spdx-licenses": "1.5.8",
+        "composer/xdebug-handler": "3.0.5",
+        "dealerdirect/phpcodesniffer-composer-installer": "v1.0.0",
+        "doctrine/instantiator": "2.0.0",
+        "drupal/coder": "8.3.26",
+        "google/protobuf": "v4.29.1",
+        "justinrainbow/json-schema": "5.3.0",
+        "lullabot/mink-selenium2-driver": "v1.7.4",
+        "lullabot/php-webdriver": "v2.0.6",
+        "mglaman/phpstan-drupal": "2.0.0",
+        "micheh/phpcs-gitlab": "1.1.0",
+        "mikey179/vfsstream": "v1.6.12",
+        "myclabs/deep-copy": "1.12.1",
+        "nikic/php-parser": "v5.3.1",
+        "nyholm/psr7-server": "1.1.0",
+        "open-telemetry/api": "1.1.1",
+        "open-telemetry/context": "1.1.0",
+        "open-telemetry/exporter-otlp": "1.1.0",
+        "open-telemetry/gen-otlp-protobuf": "1.2.1",
+        "open-telemetry/sdk": "1.1.2",
+        "open-telemetry/sem-conv": "1.27.1",
+        "phar-io/manifest": "2.0.4",
+        "phar-io/version": "3.2.1",
+        "php-http/discovery": "1.20.0",
+        "php-http/guzzle7-adapter": "1.1.0",
+        "php-http/httplug": "2.4.1",
+        "php-http/promise": "1.3.1",
+        "phpdocumentor/reflection-common": "2.2.0",
+        "phpdocumentor/reflection-docblock": "5.6.1",
+        "phpdocumentor/type-resolver": "1.10.0",
+        "phpspec/prophecy": "v1.20.0",
+        "phpspec/prophecy-phpunit": "v2.3.0",
+        "phpstan/extension-installer": "1.4.3",
+        "phpstan/phpdoc-parser": "1.33.0",
+        "phpstan/phpstan": "2.0.4",
+        "phpstan/phpstan-deprecation-rules": "2.0.1",
+        "phpstan/phpstan-phpunit": "2.0.1",
+        "phpunit/php-code-coverage": "10.1.16",
+        "phpunit/php-file-iterator": "4.1.0",
+        "phpunit/php-invoker": "4.0.0",
+        "phpunit/php-text-template": "3.0.1",
+        "phpunit/php-timer": "6.0.0",
+        "phpunit/phpunit": "10.5.38",
+        "ramsey/collection": "2.0.0",
+        "ramsey/uuid": "4.7.6",
+        "react/promise": "v3.2.0",
+        "sebastian/cli-parser": "2.0.1",
+        "sebastian/code-unit": "2.0.0",
+        "sebastian/code-unit-reverse-lookup": "3.0.0",
+        "sebastian/comparator": "5.0.3",
+        "sebastian/complexity": "3.2.0",
+        "sebastian/environment": "6.1.0",
+        "sebastian/exporter": "5.1.2",
+        "sebastian/global-state": "6.0.2",
+        "sebastian/lines-of-code": "2.0.2",
+        "sebastian/object-enumerator": "5.0.0",
+        "sebastian/object-reflector": "3.0.0",
+        "sebastian/recursion-context": "5.0.0",
+        "sebastian/type": "4.0.0",
+        "sebastian/version": "4.0.1",
+        "seld/jsonlint": "1.11.0",
+        "seld/phar-utils": "1.2.1",
+        "seld/signal-handler": "2.0.2",
+        "sirbrillig/phpcs-variable-analysis": "v2.11.21",
+        "slevomat/coding-standard": "8.15.0",
+        "squizlabs/php_codesniffer": "3.11.1",
+        "symfony/browser-kit": "v7.2.0",
+        "symfony/css-selector": "v7.2.0",
+        "symfony/dom-crawler": "v7.2.0",
+        "symfony/lock": "v7.2.0",
+        "tbachert/spi": "v1.0.2",
+        "theseer/tokenizer": "1.2.3",
+        "webflo/drupal-finder": "1.3.1",
+        "webmozart/assert": "1.11.0"
+    }
+}

composer/Metapackage/README.txt

+# Drupal Metapackages
+
+A metapackage is a Composer package that contains only a composer.json, and
+has no other content. In other words, the purpose of a metapackage is to
+provide dependencies, not to provide code or data.
+
+
+## Metapackages Provided by Drupal Core
+
+Drupal Core provides three metapackages that serve different purposes.
+
+ - drupal/core-recommended: This project pins to the exact version of each
+   dependency used in drupal/core. It also requires drupal/core, so
+   drupal/core-recommended should be used INSTEAD OF drupal/core. See usage
+   diagram below. This relationship makes it easier for Composer to update
+   a Drupal project.
+
+ - drupal/core-dev: This project provides the same version constraints as Drupal
+   uses for testing. It is useful for projects that either wish to run some of
+   the Drupal tests directly, or for projects that may wish to use the same
+   components that Drupal does for testing.
+
+ - drupal/core-dev-pinned: This project should be used INSTEAD OF
+   drupal/core-dev in instances where a project wishes to pin to the exact
+   version of each testing dependency used in Drupal. This in general should not
+   be necessary.
+
+Note that a project that uses both drupal/core-recommended and
+drupal/core-dev-pinned must update them both at the same time, e.g.:
+
+  composer update drupal/core-recommended drupal/core-dev-pinned --with-dependencies
+
+Composer may have trouble with the update if one of these projects is listed
+on the command line without the other. Running composer update without any
+parameters should also work, because in this instance every dependency is
+updated.
+
+
+## Metapackage Usage in Template Projects
+
+The relationship between the metapackages drupal/core-recommended and
+drupal/core-dev and the project (subtree split) drupal/core, as used in the
+drupal/recommended-project is shown below:
+
++----------------------------+
+| drupal/recommended-project |
++----------------------------+
+ |
+ +--"require":
+ |    |
+ |    |   +-------------------------+   +-------------+
+ |    +-->| drupal/core-recommended |-->| drupal/core |
+ |        +-------------------------+   +-------------+
+ |
+ +--"require-dev":
+      |
+      |   +-------------------------+
+      +-->| drupal/core-dev         |
+          +-------------------------+
+
+If a user does not wish to pin their Drupal project's dependencies to the same
+versions used in drupal/core, then they should replace drupal/core-recommended
+with drupal/core in their "require" section.
+
+If a user does not need the testing dependencies in their Drupal project, then
+they may simply remove drupal/core-dev from the "require-dev" section.

composer/Plugin/ProjectMessage/LICENSE.txt

+        GNU GENERAL PUBLIC LICENSE
+           Version 2, June 1991
+
+ Copyright (C) 1989, 1991 Free Software Foundation, Inc.,
+ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+          Preamble
+
+  The licenses for most software are designed to take away your
+freedom to share and change it.  By contrast, the GNU General Public
+License is intended to guarantee your freedom to share and change free
+software--to make sure the software is free for all its users.  This
+General Public License applies to most of the Free Software
+Foundation's software and to any other program whose authors commit to
+using it.  (Some other Free Software Foundation software is covered by
+the GNU Lesser General Public License instead.)  You can apply it to
+your programs, too.
+
+  When we speak of free software, we are referring to freedom, not
+price.  Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
+this service if you wish), that you receive source code or can get it
+if you want it, that you can change the software or use pieces of it
+in new free programs; and that you know you can do these things.
+
+  To protect your rights, we need to make restrictions that forbid
+anyone to deny you these rights or to ask you to surrender the rights.
+These restrictions translate to certain responsibilities for you if you
+distribute copies of the software, or if you modify it.
+
+  For example, if you distribute copies of such a program, whether
+gratis or for a fee, you must give the recipients all the rights that
+you have.  You must make sure that they, too, receive or can get the
+source code.  And you must show them these terms so they know their
+rights.
+
+  We protect your rights with two steps: (1) copyright the software, and
+(2) offer you this license which gives you legal permission to copy,
+distribute and/or modify the software.
+
+  Also, for each author's protection and ours, we want to make certain
+that everyone understands that there is no warranty for this free
+software.  If the software is modified by someone else and passed on, we
+want its recipients to know that what they have is not the original, so
+that any problems introduced by others will not reflect on the original
+authors' reputations.
+
+  Finally, any free program is threatened constantly by software
+patents.  We wish to avoid the danger that redistributors of a free
+program will individually obtain patent licenses, in effect making the
+program proprietary.  To prevent this, we have made it clear that any
+patent must be licensed for everyone's free use or not licensed at all.
+
+  The precise terms and conditions for copying, distribution and
+modification follow.
+
+        GNU GENERAL PUBLIC LICENSE
+   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
+
+  0. This License applies to any program or other work which contains
+a notice placed by the copyright holder saying it may be distributed
+under the terms of this General Public License.  The "Program", below,
+refers to any such program or work, and a "work based on the Program"
+means either the Program or any derivative work under copyright law:
+that is to say, a work containing the Program or a portion of it,
+either verbatim or with modifications and/or translated into another
+language.  (Hereinafter, translation is included without limitation in
+the term "modification".)  Each licensee is addressed as "you".
+
+Activities other than copying, distribution and modification are not
+covered by this License; they are outside its scope.  The act of
+running the Program is not restricted, and the output from the Program
+is covered only if its contents constitute a work based on the
+Program (independent of having been made by running the Program).
+Whether that is true depends on what the Program does.
+
+  1. You may copy and distribute verbatim copies of the Program's
+source code as you receive it, in any medium, provided that you
+conspicuously and appropriately publish on each copy an appropriate
+copyright notice and disclaimer of warranty; keep intact all the
+notices that refer to this License and to the absence of any warranty;
+and give any other recipients of the Program a copy of this License
+along with the Program.
+
+You may charge a fee for the physical act of transferring a copy, and
+you may at your option offer warranty protection in exchange for a fee.
+
+  2. You may modify your copy or copies of the Program or any portion
+of it, thus forming a work based on the Program, and copy and
+distribute such modifications or work under the terms of Section 1
+above, provided that you also meet all of these conditions:
+
+    a) You must cause the modified files to carry prominent notices
+    stating that you changed the files and the date of any change.
+
+    b) You must cause any work that you distribute or publish, that in
+    whole or in part contains or is derived from the Program or any
+    part thereof, to be licensed as a whole at no charge to all third
+    parties under the terms of this License.
+
+    c) If the modified program normally reads commands interactively
+    when run, you must cause it, when started running for such
+    interactive use in the most ordinary way, to print or display an
+    announcement including an appropriate copyright notice and a
+    notice that there is no warranty (or else, saying that you provide
+    a warranty) and that users may redistribute the program under
+    these conditions, and telling the user how to view a copy of this
+    License.  (Exception: if the Program itself is interactive but
+    does not normally print such an announcement, your work based on
+    the Program is not required to print an announcement.)
+
+These requirements apply to the modified work as a whole.  If
+identifiable sections of that work are not derived from the Program,
+and can be reasonably considered independent and separate works in
+themselves, then this License, and its terms, do not apply to those
+sections when you distribute them as separate works.  But when you
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+
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+
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+distribution of the source code, even though third parties are not
+compelled to copy the source along with the object code.
+
+  4. You may not copy, modify, sublicense, or distribute the Program
+except as expressly provided under this License.  Any attempt
+otherwise to copy, modify, sublicense or distribute the Program is
+void, and will automatically terminate your rights under this License.
+However, parties who have received copies, or rights, from you under
+this License will not have their licenses terminated so long as such
+parties remain in full compliance.
+
+  5. You are not required to accept this License, since you have not
+signed it.  However, nothing else grants you permission to modify or
+distribute the Program or its derivative works.  These actions are
+prohibited by law if you do not accept this License.  Therefore, by
+modifying or distributing the Program (or any work based on the
+Program), you indicate your acceptance of this License to do so, and
+all its terms and conditions for copying, distributing or modifying
+the Program or works based on it.
+
+  6. Each time you redistribute the Program (or any work based on the
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+  7. If, as a consequence of a court judgment or allegation of patent
+infringement or for any other reason (not limited to patent issues),
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+
+This section is intended to make thoroughly clear what is believed to
+be a consequence of the rest of this License.
+
+  8. If the distribution and/or use of the Program is restricted in
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+original copyright holder who places the Program under this License
+may add an explicit geographical distribution limitation excluding
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+
+  9. The Free Software Foundation may publish revised and/or new versions
+of the General Public License from time to time.  Such new versions will
+be similar in spirit to the present version, but may differ in detail to
+address new problems or concerns.
+
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+specifies a version number of this License which applies to it and "any
+later version", you have the option of following the terms and conditions
+either of that version or of any later version published by the Free
+Software Foundation.  If the Program does not specify a version number of
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+Foundation.
+
+  10. If you wish to incorporate parts of the Program into other free
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+          NO WARRANTY
+
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+
+         END OF TERMS AND CONDITIONS
+
+      How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+convey the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License along
+    with this program; if not, write to the Free Software Foundation, Inc.,
+    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+Also add information on how to contact you by electronic and paper mail.
+
+If the program is interactive, make it output a short notice like this
+when it starts in an interactive mode:
+
+    Gnomovision version 69, Copyright (C) year name of author
+    Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, the commands you use may
+be called something other than `show w' and `show c'; they could even be
+mouse-clicks or menu items--whatever suits your program.
+
+You should also get your employer (if you work as a programmer) or your
+school, if any, to sign a "copyright disclaimer" for the program, if
+necessary.  Here is a sample; alter the names:
+
+  Yoyodyne, Inc., hereby disclaims all copyright interest in the program
+  `Gnomovision' (which makes passes at compilers) written by James Hacker.
+
+  <signature of Ty Coon>, 1 April 1989
+  Ty Coon, President of Vice
+
+This General Public License does not permit incorporating your program into
+proprietary programs.  If your program is a subroutine library, you may
+consider it more useful to permit linking proprietary applications with the
+library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.

composer/Plugin/ProjectMessage/Message.php

+<?php
+
+namespace Drupal\Composer\Plugin\ProjectMessage;
+
+use Composer\Package\RootPackageInterface;
+
+/**
+ * Determine configuration.
+ *
+ * @internal
+ */
+class Message {
+
+  /**
+   * The root package.
+   *
+   * @var \Composer\Package\RootPackageInterface
+   */
+  protected $rootPackage;
+
+  /**
+   * The name of the event.
+   *
+   * @var string
+   */
+  protected $eventName;
+
+  /**
+   * The message to display.
+   *
+   * @var string[]
+   */
+  protected $messageText = [];
+
+  /**
+   * Construct a Config object.
+   *
+   * @param \Composer\Package\RootPackageInterface $root_package
+   *   Composer package object for the root package.
+   * @param string $event_name
+   *   The event name.
+   */
+  public function __construct(RootPackageInterface $root_package, $event_name) {
+    $this->rootPackage = $root_package;
+    $this->eventName = $event_name;
+  }
+
+  public function getText() {
+    if ($this->messageText) {
+      return $this->messageText;
+    }
+    $package_config = $this->rootPackage->getExtra();
+    $file = $this->eventName . '-message.txt';
+    if ($config_file = $package_config['drupal-core-project-message'][$this->eventName . '-file'] ?? FALSE) {
+      $file = $config_file;
+    }
+
+    $message = $package_config['drupal-core-project-message'][$this->eventName . '-message'] ?? [];
+
+    if ($message) {
+      $this->messageText = $message;
+    }
+    else {
+      $this->messageText = $this->getMessageFromFile($file);
+    }
+
+    // Include structured support info from composer.json.
+    if ($config_keys = $package_config['drupal-core-project-message']['include-keys'] ?? FALSE) {
+      foreach ($config_keys as $config_key) {
+        switch ($config_key) {
+          case 'name':
+            if ($homepage = $this->rootPackage->getName()) {
+              $this->messageText[] = '  * Name: ' . $homepage;
+            }
+            break;
+
+          case 'description':
+            if ($homepage = $this->rootPackage->getDescription()) {
+              $this->messageText[] = '  * Description: ' . $homepage;
+            }
+            break;
+
+          case 'homepage':
+            if ($homepage = $this->rootPackage->getHomepage()) {
+              $this->messageText[] = '  * Homepage: ' . $homepage;
+            }
+            break;
+
+          case 'support':
+            if ($support = $this->rootPackage->getSupport()) {
+              $this->messageText[] = '  * Support:';
+              foreach ($support as $support_key => $support_value) {
+                $this->messageText[] = '    * ' . $support_key . ': ' . $support_value;
+              }
+            }
+            break;
+        }
+      }
+    }
+
+    return $this->messageText;
+  }
+
+  /**
+   * Reads the message file as an array.
+   *
+   * @param string $file
+   *   The file to read. Relative paths are relative to the project directory.
+   *
+   * @return string[]
+   *   The message text.
+   */
+  protected function getMessageFromFile($file) {
+    return file_exists($file) ? file($file, FILE_IGNORE_NEW_LINES) : [];
+  }
+
+}

composer/Plugin/ProjectMessage/MessagePlugin.php

+<?php
+
+namespace Drupal\Composer\Plugin\ProjectMessage;
+
+use Composer\Composer;
+use Composer\EventDispatcher\EventSubscriberInterface;
+use Composer\IO\IOInterface;
+use Composer\Plugin\PluginInterface;
+use Composer\Script\Event;
+use Composer\Script\ScriptEvents;
+
+/**
+ * A Composer plugin to display a message after creating a project.
+ *
+ * @internal
+ */
+class MessagePlugin implements PluginInterface, EventSubscriberInterface {
+
+  /**
+   * Composer object.
+   *
+   * @var \Composer\Composer
+   */
+  protected $composer;
+
+  /**
+   * IO object.
+   *
+   * @var \Composer\IO\IOInterface
+   */
+  protected $io;
+
+  /**
+   * Configuration.
+   *
+   * @var \Drupal\Composer\Plugin\VendorHardening\Config
+   */
+  protected $config;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function activate(Composer $composer, IOInterface $io) {
+    $this->composer = $composer;
+    $this->io = $io;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function deactivate(Composer $composer, IOInterface $io) {
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function uninstall(Composer $composer, IOInterface $io) {
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getSubscribedEvents() {
+    return [
+      ScriptEvents::POST_CREATE_PROJECT_CMD => 'displayPostCreateMessage',
+      ScriptEvents::POST_INSTALL_CMD => 'displayPostCreateMessage',
+    ];
+  }
+
+  public function displayPostCreateMessage(Event $event) {
+    $message = new Message($this->composer->getPackage(), $event->getName());
+    if ($message = $message->getText()) {
+      $this->io->write($message);
+    }
+  }
+
+}

composer/Plugin/ProjectMessage/README.md

+The Drupal Project Message Plugin
+=================================
+
+Thanks for using this Drupal component.
+
+You can participate in its development on Drupal.org, through our issue system:
+https://www.drupal.org/project/issues/drupal
+
+You can get the full Drupal repo here:
+https://www.drupal.org/project/drupal/git-instructions
+
+You can browse the full Drupal repo here:
+https://git.drupalcode.org/project/drupal
+
+What does it do?
+----------------
+
+This Composer plugin displays a configurable message after Composer installation
+processes have finished.
+
+This is ideal for a 'next steps' type prompt to help get the user oriented.
+
+Currently only two Composer events are supported:
+- post-create-project-cmd, when a `composer create-project` command has
+  finished.
+- post-install-cmd, when a `composer install` command has finished.
+
+How do I set it up?
+-------------------
+
+Require this Composer plugin in your project template composer.json file:
+
+    "require": {
+      "drupal/core-project-message": "^8.8"
+    }
+
+### Configuration
+
+There are three ways to configure this plugin to output information:
+- Using a text file.
+- Using composer.json schema keys.
+- Embedding the information in the extra section of the composer.json file.
+
+### Using a text file
+
+By default, the plugin will respond to `post-install-cmd` or
+`post-create-project-cmd` Composer events by looking for a similarly-named file
+in the root of the project. For instance, if the user issues a `composer
+create-project` command, when that command is finished, the plugin will look for
+a file named `post-create-project-cmd-message.txt` and then display it on the
+command line.
+
+The file should be plain text, with markup suitable for Symfony's
+`OutputInterface::writeln()` method. See documentation here:
+https://symfony.com/doc/3.4/console/coloring.html
+
+You can also configure your own file(s), using the `extra` section of your
+composer.json file:
+
+    "extra": {
+      "drupal-core-project-message": {
+        "post-create-project-cmd-file": "bespoke/special_file.txt"
+      }
+    }
+
+### Using composer.json schema keys
+
+You can tell the plugin to output the structured support information from the
+composer.json file by telling it the keys you wish to display.
+
+Currently, only `name`, `description`, `homepage` and `support` are supported.
+
+    "extra": {
+        "drupal-core-project-message": {
+            "include-keys": ["homepage", "support"],
+        }
+    }
+
+Then you can include this information in your composer.json file, which you
+should probably be doing anyway.
+
+### Embedding the information in the extra section
+
+You can specify text directly within the `extra` section by using the
+`[event-name]-message` key. This message should be an array, with one string for
+each line:
+
+    "extra": {
+      "drupal-core-project-message": {
+        "post-create-project-cmd-message": [
+          "Thanks for installing this project.",
+          "Read our documentation here: http://example.com/docs"
+        ]
+      }
+    }
+
+These strings should be plain text, with markup suitable for Symfony's
+`OutputInterface::writeln()` method. See documentation here:
+https://symfony.com/doc/3.4/console/coloring.html
+
+The `-message` section will always override `-file` for a given event.

composer/Plugin/ProjectMessage/TESTING.txt

+HOW-TO: Test this Drupal component
+
+In order to test this component, you'll need to get the entire Drupal repo and
+run the tests there.
+
+You'll find the tests under core/tests/Drupal/Tests/Plugin.
+
+You can get the full Drupal repo here:
+https://www.drupal.org/project/drupal/git-instructions
+
+You can find more information about running PHPUnit tests with Drupal here:
+https://www.drupal.org/node/2116263
+
+Each component in the Drupal\Composer namespace has its own annotated test
+group. You can use this group to run only the tests for this component. Like
+this:
+
+$ ./vendor/bin/phpunit -c core --group ProjectMessage

composer/Plugin/ProjectMessage/composer.json

+{
+  "name": "drupal/core-project-message",
+  "description": "Adds a message after Composer installation.",
+  "keywords": ["drupal"],
+  "homepage": "https://www.drupal.org/project/drupal",
+  "license": "GPL-2.0-or-later",
+  "type": "composer-plugin",
+  "autoload": {
+    "psr-4": {
+      "Drupal\\Composer\\Plugin\\ProjectMessage\\": "."
+    }
+  },
+  "extra": {
+    "class": "Drupal\\Composer\\Plugin\\ProjectMessage\\MessagePlugin"
+  },
+  "require": {
+    "php": ">=7.3.0",
+    "composer-plugin-api": "^2"
+  }
+}