Allow to choose an index for tagged collection

src/Symfony/Component/DependencyInjection/Argument/TaggedIteratorArgument.php

@@ -19,16 +19,33 @@ namespace Symfony\Component\DependencyInjection\Argument;
 class TaggedIteratorArgument extends IteratorArgument
 {
     private $tag;
+    private $indexAttribute;
+    private $defaultIndexMethod;
 
-    public function __construct(string $tag)
+    public function __construct(string $tag, string $indexAttribute = null, string $defaultIndexMethod = null)
     {
         parent::__construct([]);
 
         $this->tag = $tag;
+        $this->indexAttribute = $indexAttribute ?: null;
+
+        if ($indexAttribute) {
+            $this->defaultIndexMethod = $defaultIndexMethod ?: ('getDefault'.str_replace(' ', '', ucwords(preg_replace('/[^a-zA-Z0-9\x7f-\xff]++/', ' ', $indexAttribute))).'Name');
+        }
     }
 
     public function getTag()
     {
         return $this->tag;
     }
+
+    public function getIndexAttribute(): ?string
+    {
+        return $this->indexAttribute;
+    }
+
+    public function getDefaultIndexMethod(): ?string
+    {
+        return $this->defaultIndexMethod;
+    }
 }

src/Symfony/Component/DependencyInjection/Compiler/PriorityTaggedServiceTrait.php

@@ -11,7 +11,9 @@
 
 namespace Symfony\Component\DependencyInjection\Compiler;
 
+use Symfony\Component\DependencyInjection\Argument\TaggedIteratorArgument;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
+use Symfony\Component\DependencyInjection\Exception\InvalidArgumentException;
 use Symfony\Component\DependencyInjection\Reference;
 
 /**
@@ -31,18 +33,59 @@ trait PriorityTaggedServiceTrait
      * @see https://bugs.php.net/bug.php?id=53710
      * @see https://bugs.php.net/bug.php?id=60926
      *
-     * @param string           $tagName
-     * @param ContainerBuilder $container
+     * @param string|TaggedIteratorArgument $tagName
+     * @param ContainerBuilder              $container
      *
      * @return Reference[]
      */
     private function findAndSortTaggedServices($tagName, ContainerBuilder $container)
     {
+        $indexAttribute = $defaultIndexMethod = null;
+        if ($tagName instanceof TaggedIteratorArgument) {
+            $indexAttribute = $tagName->getIndexAttribute();
+            $defaultIndexMethod = $tagName->getDefaultIndexMethod();
+            $tagName = $tagName->getTag();
+        }
         $services = [];
 
         foreach ($container->findTaggedServiceIds($tagName, true) as $serviceId => $attributes) {
             $priority = isset($attributes[0]['priority']) ? $attributes[0]['priority'] : 0;
-            $services[$priority][] = new Reference($serviceId);
+
+            if (null === $indexAttribute) {
+                $services[$priority][] = new Reference($serviceId);
+
+                continue;
+            }
+
+            if (isset($attributes[0][$indexAttribute])) {
+                $services[$priority][$attributes[0][$indexAttribute]] = new Reference($serviceId);
+
+                continue;
+            }
+
+            if (!$r = $container->getReflectionClass($class = $container->getDefinition($serviceId)->getClass())) {
+                throw new InvalidArgumentException(sprintf('Class "%s" used for service "%s" cannot be found.', $class, $serviceId));
+            }
+
+            if (!$r->hasMethod($defaultIndexMethod)) {
+                throw new InvalidArgumentException(sprintf('Method "%s::%s()" not found: tag "%s" on service "%s" is missing "%s" attribute.', $class, $defaultIndexMethod, $tagName, $serviceId, $indexAttribute));
+            }
+
+            if (!($rm = $r->getMethod($defaultIndexMethod))->isStatic()) {
+                throw new InvalidArgumentException(sprintf('Method "%s::%s()" should be static: tag "%s" on service "%s" is missing "%s" attribute.', $class, $defaultIndexMethod, $tagName, $serviceId, $indexAttribute));
+            }
+
+            if (!$rm->isPublic()) {
+                throw new InvalidArgumentException(sprintf('Method "%s::%s()" should be public: tag "%s" on service "%s" is missing "%s" attribute.', $class, $defaultIndexMethod, $tagName, $serviceId, $indexAttribute));
+            }
+
+            $key = $rm->invoke(null);
+
+            if (!\is_string($key)) {
+                throw new InvalidArgumentException(sprintf('Method "%s::%s()" should return a string, got %s: tag "%s" on service "%s" is missing "%s" attribute.', $class, $defaultIndexMethod, \gettype($key), $tagName, $serviceId, $indexAttribute));
+            }
+
+            $services[$priority][$key] = new Reference($serviceId);
         }
 
         if ($services) {

src/Symfony/Component/DependencyInjection/Compiler/ResolveTaggedIteratorArgumentPass.php

@@ -31,7 +31,7 @@ class ResolveTaggedIteratorArgumentPass extends AbstractRecursivePass
             return parent::processValue($value, $isRoot);
         }
 
-        $value->setValues($this->findAndSortTaggedServices($value->getTag(), $this->container));
+        $value->setValues($this->findAndSortTaggedServices($value, $this->container));
 
         return $value;
     }

src/Symfony/Component/DependencyInjection/Loader/Configurator/ContainerConfigurator.php

@@ -116,9 +116,9 @@ function iterator(array $values): IteratorArgument
 /**
  * Creates a lazy iterator by tag name.
  */
-function tagged(string $tag): TaggedIteratorArgument
+function tagged(string $tag, string $indexAttribute = null, string $defaultIndexMethod = null): TaggedIteratorArgument
 {
-    return new TaggedIteratorArgument($tag);
+    return new TaggedIteratorArgument($tag, $indexAttribute, $defaultIndexMethod);
 }
 
 /**

src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php

@@ -710,11 +710,17 @@ class YamlFileLoader extends FileLoader
                 }
             }
             if ('tagged' === $value->getTag()) {
-                if (!\is_string($argument) || !$argument) {
-                    throw new InvalidArgumentException(sprintf('"!tagged" tag only accepts non empty string in "%s".', $file));
+                if (\is_string($argument) && $argument) {
+                    return new TaggedIteratorArgument($argument);
                 }
+                if (\is_array($argument) && isset($argument['name']) && $argument['name']) {
+                    if (array_diff(array_keys($argument), ['name', 'index_by', 'default_index_method'])) {
+                        throw new InvalidArgumentException('"!tagged" tag contains unsupported keys. Supported are: "name, index_by, default_index_method".');
+                    }
 
-                return new TaggedIteratorArgument($argument);
+                    return new TaggedIteratorArgument($argument['name'], $argument['index_by'] ?? null, $argument['default_index_method'] ?? null);
+                }
+                throw new InvalidArgumentException(sprintf('"!tagged" tag only accepts a non empty string or an array with a key "name" in "%s".', $file));
             }
             if ('service' === $value->getTag()) {
                 if ($isParameter) {