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    <h3>Editing: YamlFileLoader.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier &lt;fabien@symfony.com&gt;
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Symfony\Component\Routing\Loader;

use Symfony\Component\Config\Loader\FileLoader;
use Symfony\Component\Config\Resource\FileResource;
use Symfony\Component\Routing\Loader\Configurator\Traits\HostTrait;
use Symfony\Component\Routing\Loader\Configurator\Traits\LocalizedRouteTrait;
use Symfony\Component\Routing\Loader\Configurator\Traits\PrefixTrait;
use Symfony\Component\Routing\RouteCollection;
use Symfony\Component\Yaml\Exception\ParseException;
use Symfony\Component\Yaml\Parser as YamlParser;
use Symfony\Component\Yaml\Yaml;

/**
 * YamlFileLoader loads Yaml routing files.
 *
 * @author Fabien Potencier &lt;fabien@symfony.com&gt;
 * @author Tobias Schultze &lt;http://tobion.de&gt;
 */
class YamlFileLoader extends FileLoader
{
    use HostTrait;
    use LocalizedRouteTrait;
    use PrefixTrait;

    private const AVAILABLE_KEYS = [
        'resource', 'type', 'prefix', 'path', 'host', 'schemes', 'methods', 'defaults', 'requirements', 'options', 'condition', 'controller', 'name_prefix', 'trailing_slash_on_root', 'locale', 'format', 'utf8', 'exclude', 'stateless',
    ];
    private $yamlParser;

    /**
     * Loads a Yaml file.
     *
     * @param string      $file A Yaml file path
     * @param string|null $type The resource type
     *
     * @return RouteCollection
     *
     * @throws \InvalidArgumentException When a route can't be parsed because YAML is invalid
     */
    public function load($file, ?string $type = null)
    {
        $path = $this-&gt;locator-&gt;locate($file);

        if (!stream_is_local($path)) {
            throw new \InvalidArgumentException(sprintf('This is not a local file &quot;%s&quot;.', $path));
        }

        if (!file_exists($path)) {
            throw new \InvalidArgumentException(sprintf('File &quot;%s&quot; not found.', $path));
        }

        if (null === $this-&gt;yamlParser) {
            $this-&gt;yamlParser = new YamlParser();
        }

        try {
            $parsedConfig = $this-&gt;yamlParser-&gt;parseFile($path, Yaml::PARSE_CONSTANT);
        } catch (ParseException $e) {
            throw new \InvalidArgumentException(sprintf('The file &quot;%s&quot; does not contain valid YAML: ', $path).$e-&gt;getMessage(), 0, $e);
        }

        $collection = new RouteCollection();
        $collection-&gt;addResource(new FileResource($path));

        // empty file
        if (null === $parsedConfig) {
            return $collection;
        }

        // not an array
        if (!\is_array($parsedConfig)) {
            throw new \InvalidArgumentException(sprintf('The file &quot;%s&quot; must contain a YAML array.', $path));
        }

        foreach ($parsedConfig as $name =&gt; $config) {
            if (0 === strpos($name, 'when@')) {
                if (!$this-&gt;env || 'when@'.$this-&gt;env !== $name) {
                    continue;
                }

                foreach ($config as $name =&gt; $config) {
                    $this-&gt;validate($config, $name.'&quot; when &quot;@'.$this-&gt;env, $path);

                    if (isset($config['resource'])) {
                        $this-&gt;parseImport($collection, $config, $path, $file);
                    } else {
                        $this-&gt;parseRoute($collection, $name, $config, $path);
                    }
                }

                continue;
            }

            $this-&gt;validate($config, $name, $path);

            if (isset($config['resource'])) {
                $this-&gt;parseImport($collection, $config, $path, $file);
            } else {
                $this-&gt;parseRoute($collection, $name, $config, $path);
            }
        }

        return $collection;
    }

    /**
     * {@inheritdoc}
     */
    public function supports($resource, ?string $type = null)
    {
        return \is_string($resource) &amp;&amp; \in_array(pathinfo($resource, \PATHINFO_EXTENSION), ['yml', 'yaml'], true) &amp;&amp; (!$type || 'yaml' === $type);
    }

    /**
     * Parses a route and adds it to the RouteCollection.
     */
    protected function parseRoute(RouteCollection $collection, string $name, array $config, string $path)
    {
        if (isset($config['alias'])) {
            $alias = $collection-&gt;addAlias($name, $config['alias']);
            $deprecation = $config['deprecated'] ?? null;
            if (null !== $deprecation) {
                $alias-&gt;setDeprecated(
                    $deprecation['package'],
                    $deprecation['version'],
                    $deprecation['message'] ?? ''
                );
            }

            return;
        }

        $defaults = $config['defaults'] ?? [];
        $requirements = $config['requirements'] ?? [];
        $options = $config['options'] ?? [];

        foreach ($requirements as $placeholder =&gt; $requirement) {
            if (\is_int($placeholder)) {
                throw new \InvalidArgumentException(sprintf('A placeholder name must be a string (%d given). Did you forget to specify the placeholder key for the requirement &quot;%s&quot; of route &quot;%s&quot; in &quot;%s&quot;?', $placeholder, $requirement, $name, $path));
            }
        }

        if (isset($config['controller'])) {
            $defaults['_controller'] = $config['controller'];
        }
        if (isset($config['locale'])) {
            $defaults['_locale'] = $config['locale'];
        }
        if (isset($config['format'])) {
            $defaults['_format'] = $config['format'];
        }
        if (isset($config['utf8'])) {
            $options['utf8'] = $config['utf8'];
        }
        if (isset($config['stateless'])) {
            $defaults['_stateless'] = $config['stateless'];
        }

        $routes = $this-&gt;createLocalizedRoute($collection, $name, $config['path']);
        $routes-&gt;addDefaults($defaults);
        $routes-&gt;addRequirements($requirements);
        $routes-&gt;addOptions($options);
        $routes-&gt;setSchemes($config['schemes'] ?? []);
        $routes-&gt;setMethods($config['methods'] ?? []);
        $routes-&gt;setCondition($config['condition'] ?? null);

        if (isset($config['host'])) {
            $this-&gt;addHost($routes, $config['host']);
        }
    }

    /**
     * Parses an import and adds the routes in the resource to the RouteCollection.
     */
    protected function parseImport(RouteCollection $collection, array $config, string $path, string $file)
    {
        $type = $config['type'] ?? null;
        $prefix = $config['prefix'] ?? '';
        $defaults = $config['defaults'] ?? [];
        $requirements = $config['requirements'] ?? [];
        $options = $config['options'] ?? [];
        $host = $config['host'] ?? null;
        $condition = $config['condition'] ?? null;
        $schemes = $config['schemes'] ?? null;
        $methods = $config['methods'] ?? null;
        $trailingSlashOnRoot = $config['trailing_slash_on_root'] ?? true;
        $namePrefix = $config['name_prefix'] ?? null;
        $exclude = $config['exclude'] ?? null;

        if (isset($config['controller'])) {
            $defaults['_controller'] = $config['controller'];
        }
        if (isset($config['locale'])) {
            $defaults['_locale'] = $config['locale'];
        }
        if (isset($config['format'])) {
            $defaults['_format'] = $config['format'];
        }
        if (isset($config['utf8'])) {
            $options['utf8'] = $config['utf8'];
        }
        if (isset($config['stateless'])) {
            $defaults['_stateless'] = $config['stateless'];
        }

        $this-&gt;setCurrentDir(\dirname($path));

        /** @var RouteCollection[] $imported */
        $imported = $this-&gt;import($config['resource'], $type, false, $file, $exclude) ?: [];

        if (!\is_array($imported)) {
            $imported = [$imported];
        }

        foreach ($imported as $subCollection) {
            $this-&gt;addPrefix($subCollection, $prefix, $trailingSlashOnRoot);

            if (null !== $host) {
                $this-&gt;addHost($subCollection, $host);
            }
            if (null !== $condition) {
                $subCollection-&gt;setCondition($condition);
            }
            if (null !== $schemes) {
                $subCollection-&gt;setSchemes($schemes);
            }
            if (null !== $methods) {
                $subCollection-&gt;setMethods($methods);
            }
            if (null !== $namePrefix) {
                $subCollection-&gt;addNamePrefix($namePrefix);
            }
            $subCollection-&gt;addDefaults($defaults);
            $subCollection-&gt;addRequirements($requirements);
            $subCollection-&gt;addOptions($options);

            $collection-&gt;addCollection($subCollection);
        }
    }

    /**
     * Validates the route configuration.
     *
     * @param array  $config A resource config
     * @param string $name   The config key
     * @param string $path   The loaded file path
     *
     * @throws \InvalidArgumentException If one of the provided config keys is not supported,
     *                                   something is missing or the combination is nonsense
     */
    protected function validate($config, string $name, string $path)
    {
        if (!\is_array($config)) {
            throw new \InvalidArgumentException(sprintf('The definition of &quot;%s&quot; in &quot;%s&quot; must be a YAML array.', $name, $path));
        }
        if (isset($config['alias'])) {
            $this-&gt;validateAlias($config, $name, $path);

            return;
        }
        if ($extraKeys = array_diff(array_keys($config), self::AVAILABLE_KEYS)) {
            throw new \InvalidArgumentException(sprintf('The routing file &quot;%s&quot; contains unsupported keys for &quot;%s&quot;: &quot;%s&quot;. Expected one of: &quot;%s&quot;.', $path, $name, implode('&quot;, &quot;', $extraKeys), implode('&quot;, &quot;', self::AVAILABLE_KEYS)));
        }
        if (isset($config['resource']) &amp;&amp; isset($config['path'])) {
            throw new \InvalidArgumentException(sprintf('The routing file &quot;%s&quot; must not specify both the &quot;resource&quot; key and the &quot;path&quot; key for &quot;%s&quot;. Choose between an import and a route definition.', $path, $name));
        }
        if (!isset($config['resource']) &amp;&amp; isset($config['type'])) {
            throw new \InvalidArgumentException(sprintf('The &quot;type&quot; key for the route definition &quot;%s&quot; in &quot;%s&quot; is unsupported. It is only available for imports in combination with the &quot;resource&quot; key.', $name, $path));
        }
        if (!isset($config['resource']) &amp;&amp; !isset($config['path'])) {
            throw new \InvalidArgumentException(sprintf('You must define a &quot;path&quot; for the route &quot;%s&quot; in file &quot;%s&quot;.', $name, $path));
        }
        if (isset($config['controller']) &amp;&amp; isset($config['defaults']['_controller'])) {
            throw new \InvalidArgumentException(sprintf('The routing file &quot;%s&quot; must not specify both the &quot;controller&quot; key and the defaults key &quot;_controller&quot; for &quot;%s&quot;.', $path, $name));
        }
        if (isset($config['stateless']) &amp;&amp; isset($config['defaults']['_stateless'])) {
            throw new \InvalidArgumentException(sprintf('The routing file &quot;%s&quot; must not specify both the &quot;stateless&quot; key and the defaults key &quot;_stateless&quot; for &quot;%s&quot;.', $path, $name));
        }
    }

    /**
     * @throws \InvalidArgumentException If one of the provided config keys is not supported,
     *                                   something is missing or the combination is nonsense
     */
    private function validateAlias(array $config, string $name, string $path): void
    {
        foreach ($config as $key =&gt; $value) {
            if (!\in_array($key, ['alias', 'deprecated'], true)) {
                throw new \InvalidArgumentException(sprintf('The routing file &quot;%s&quot; must not specify other keys than &quot;alias&quot; and &quot;deprecated&quot; for &quot;%s&quot;.', $path, $name));
            }

            if ('deprecated' === $key) {
                if (!isset($value['package'])) {
                    throw new \InvalidArgumentException(sprintf('The routing file &quot;%s&quot; must specify the attribute &quot;package&quot; of the &quot;deprecated&quot; option for &quot;%s&quot;.', $path, $name));
                }

                if (!isset($value['version'])) {
                    throw new \InvalidArgumentException(sprintf('The routing file &quot;%s&quot; must specify the attribute &quot;version&quot; of the &quot;deprecated&quot; option for &quot;%s&quot;.', $path, $name));
                }
            }
        }
    }
}
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