feature #20973 [DI] Add getter injection (nicolas-grekas)

This PR was merged into the 3.3-dev branch.

Discussion
----------

[DI] Add getter injection

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #20657
| License       | MIT
| Doc PR        | symfony/symfony-docs#7300

Getter overriding by the container will allow a new kind of dependency injection which enables easier laziness and more immutable classes, by not requiring any corresponding setter. See linked issue for more.

This is WIP:
- [x] wire the concept
- [x] dump anonymous classes with PhpDumper
- [x] generate at runtime in ContainerBuilder::createService
- [x] tests
- [x] make it work on PHP 5

Commits
-------

cb49858 [DI] Add getter injection

src/Symfony/Component/DependencyInjection/CHANGELOG.md

@@ -4,6 +4,7 @@ CHANGELOG
 3.3.0
 -----
 
+ * [EXPERIMENTAL] added support for getter-injection
  * added support for omitting the factory class name in a service definition if the definition class is set
  * deprecated case insensitivity of service identifiers
  * added "iterator" argument type for lazy iteration over a set of values and services

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

@@ -61,6 +61,7 @@ protected function processValue($value, $isRoot = false)
         } elseif ($value instanceof Definition) {
             $value->setArguments($this->processValue($value->getArguments()));
             $value->setProperties($this->processValue($value->getProperties()));
+            $value->setOverriddenGetters($this->processValue($value->getOverriddenGetters()));
             $value->setMethodCalls($this->processValue($value->getMethodCalls()));
 
             if ($v = $value->getFactory()) {

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

@@ -88,6 +88,7 @@ private function doResolveDefinition(ChildDefinition $definition)
         $def->setClass($parentDef->getClass());
         $def->setArguments($parentDef->getArguments());
         $def->setMethodCalls($parentDef->getMethodCalls());
+        $def->setOverriddenGetters($parentDef->getOverriddenGetters());
         $def->setProperties($parentDef->getProperties());
         $def->setAutowiringTypes($parentDef->getAutowiringTypes());
         if ($parentDef->isDeprecated()) {
@@ -160,6 +161,11 @@ private function doResolveDefinition(ChildDefinition $definition)
             $def->setMethodCalls(array_merge($def->getMethodCalls(), $calls));
         }
 
+        // merge overridden getters
+        foreach ($definition->getOverriddenGetters() as $k => $v) {
+            $def->setOverriddenGetter($k, $v);
+        }
+
         // merge autowiring types
         foreach ($definition->getAutowiringTypes() as $autowiringType) {
             $def->addAutowiringType($autowiringType);

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

@@ -59,6 +59,7 @@ private function processValue($value, $rootLevel = 0, $level = 0)
             }
             $value->setArguments($this->processValue($value->getArguments(), 0));
             $value->setProperties($this->processValue($value->getProperties(), 1));
+            $value->setOverriddenGetters($this->processValue($value->getOverriddenGetters(), 1));
             $value->setMethodCalls($this->processValue($value->getMethodCalls(), 2));
         } elseif (is_array($value)) {
             $i = 0;

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

@@ -42,6 +42,7 @@ public function process(ContainerBuilder $container)
 
             $definition->setArguments($this->processArguments($definition->getArguments()));
             $definition->setMethodCalls($this->processArguments($definition->getMethodCalls()));
+            $definition->setOverriddenGetters($this->processArguments($definition->getOverriddenGetters()));
             $definition->setProperties($this->processArguments($definition->getProperties()));
             $definition->setFactory($this->processFactory($definition->getFactory()));
         }

src/Symfony/Component/DependencyInjection/ContainerBuilder.php

@@ -29,6 +29,7 @@
 use Symfony\Component\Config\Resource\ResourceInterface;
 use Symfony\Component\DependencyInjection\LazyProxy\Instantiator\InstantiatorInterface;
 use Symfony\Component\DependencyInjection\LazyProxy\Instantiator\RealServiceInstantiator;
+use Symfony\Component\DependencyInjection\LazyProxy\GetterProxyInterface;
 use Symfony\Component\ExpressionLanguage\Expression;
 use Symfony\Component\ExpressionLanguage\ExpressionFunctionProviderInterface;
 
@@ -890,6 +891,9 @@ private function createService(Definition $definition, $id, $tryProxy = true)
         $arguments = $this->resolveServices($parameterBag->unescapeValue($parameterBag->resolveValue($definition->getArguments())));
 
         if (null !== $factory = $definition->getFactory()) {
+            if ($definition->getOverriddenGetters()) {
+                throw new RuntimeException(sprintf('Cannot create service "%s": factories and overridden getters are incompatible with each other.', $id));
+            }
             if (is_array($factory)) {
                 $factory = array($this->resolveServices($parameterBag->resolveValue($factory[0])), $factory[1]);
             } elseif (!is_string($factory)) {
@@ -908,11 +912,31 @@ private function createService(Definition $definition, $id, $tryProxy = true)
         } else {
             $r = new \ReflectionClass($parameterBag->resolveValue($definition->getClass()));
 
-            $service = null === $r->getConstructor() ? $r->newInstance() : $r->newInstanceArgs($arguments);
-
             if (!$definition->isDeprecated() && 0 < strpos($r->getDocComment(), "\n * @deprecated ")) {
                 @trigger_error(sprintf('The "%s" service relies on the deprecated "%s" class. It should either be deprecated or its implementation upgraded.', $id, $r->name), E_USER_DEPRECATED);
             }
+            if ($definition->getOverriddenGetters()) {
+                static $salt;
+                if (null === $salt) {
+                    $salt = str_replace('.', '', uniqid('', true));
+                }
+                $service = sprintf('%s implements \\%s { private $container%4$s; private $values%4$s; %s }', $r->name, GetterProxyInterface::class, $this->generateOverriddenGetters($id, $definition, $r, $salt), $salt);
+                if (!class_exists($proxyClass = 'SymfonyProxy_'.md5($service), false)) {
+                    eval(sprintf('class %s extends %s', $proxyClass, $service));
+                }
+                $r = new \ReflectionClass($proxyClass);
+                $constructor = $r->getConstructor();
+                if ($constructor && !defined('HHVM_VERSION') && $constructor->getDeclaringClass()->isInternal()) {
+                    $constructor = null;
+                }
+                $service = $constructor ? $r->newInstanceWithoutConstructor() : $r->newInstanceArgs($arguments);
+                call_user_func(\Closure::bind(function ($c, $v, $s) { $this->{'container'.$s} = $c; $this->{'values'.$s} = $v; }, $service, $service), $this, $definition->getOverriddenGetters(), $salt);
+                if ($constructor) {
+                    $constructor->invokeArgs($service, $arguments);
+                }
+            } else {
+                $service = null === $r->getConstructor() ? $r->newInstance() : $r->newInstanceArgs($arguments);
+            }
         }
 
         if ($tryProxy || !$definition->isLazy()) {
@@ -1155,6 +1179,102 @@ public function getEnvCounters()
         return $this->envCounters;
     }
 
+    private function generateOverriddenGetters($id, Definition $definition, \ReflectionClass $class, $salt)
+    {
+        if ($class->isFinal()) {
+            throw new RuntimeException(sprintf('Unable to configure getter injection for service "%s": class "%s" cannot be marked as final.', $id, $class->name));
+        }
+        $getters = '';
+        foreach ($definition->getOverriddenGetters() as $name => $returnValue) {
+            $r = self::getGetterReflector($class, $name, $id, $type);
+            $visibility = $r->isProtected() ? 'protected' : 'public';
+            $name = var_export($name, true);
+            $getters .= <<<EOF
+
+{$visibility} function {$r->name}(){$type} {
+    \$c = \$this->container{$salt};
+    \$b = \$c->getParameterBag();
+    \$v = \$this->values{$salt}[{$name}];
+
+    foreach (\$c->getServiceConditionals(\$v) as \$s) {
+        if (!\$c->has(\$s)) {
+            return parent::{$r->name}();
+        }
+    }
+
+    return \$c->resolveServices(\$b->unescapeValue(\$b->resolveValue(\$v)));
+}
+EOF;
+        }
+
+        return $getters;
+    }
+
+    /**
+     * @internal
+     */
+    public static function getGetterReflector(\ReflectionClass $class, $name, $id, &$type)
+    {
+        if (!$class->hasMethod($name)) {
+            throw new RuntimeException(sprintf('Unable to configure getter injection for service "%s": method "%s::%s" does not exist.', $id, $class->name, $name));
+        }
+        $r = $class->getMethod($name);
+        if ($r->isPrivate()) {
+            throw new RuntimeException(sprintf('Unable to configure getter injection for service "%s": method "%s::%s" must be public or protected.', $id, $class->name, $r->name));
+        }
+        if ($r->isStatic()) {
+            throw new RuntimeException(sprintf('Unable to configure getter injection for service "%s": method "%s::%s" cannot be static.', $id, $class->name, $r->name));
+        }
+        if ($r->isFinal()) {
+            throw new RuntimeException(sprintf('Unable to configure getter injection for service "%s": method "%s::%s" cannot be marked as final.', $id, $class->name, $r->name));
+        }
+        if ($r->returnsReference()) {
+            throw new RuntimeException(sprintf('Unable to configure getter injection for service "%s": method "%s::%s" cannot return by reference.', $id, $class->name, $r->name));
+        }
+        if (0 < $r->getNumberOfParameters()) {
+            throw new RuntimeException(sprintf('Unable to configure getter injection for service "%s": method "%s::%s" cannot have any arguments.', $id, $class->name, $r->name));
+        }
+        if ($type = method_exists($r, 'getReturnType') ? $r->getReturnType() : null) {
+            $type = ': '.($type->allowsNull() ? '?' : '').self::generateTypeHint($type, $r);
+        }
+
+        return $r;
+    }
+
+    /**
+     * @internal
+     */
+    public static function generateTypeHint($type, \ReflectionFunctionAbstract $r)
+    {
+        if (is_string($type)) {
+            $name = $type;
+
+            if ('callable' === $name || 'array' === $name) {
+                return $name;
+            }
+        } else {
+            $name = $type instanceof \ReflectionNamedType ? $type->getName() : $type->__toString();
+
+            if ($type->isBuiltin()) {
+                return $name;
+            }
+        }
+        $lcName = strtolower($name);
+
+        if ('self' !== $lcName && 'parent' !== $lcName) {
+            return '\\'.$name;
+        }
+        if (!$r instanceof \ReflectionMethod) {
+            return;
+        }
+        if ('self' === $lcName) {
+            return '\\'.$r->getDeclaringClass()->name;
+        }
+        if ($parent = $r->getDeclaringClass()->getParentClass()) {
+            return '\\'.$parent->name;
+        }
+    }
+
     /**
      * @internal
      */

src/Symfony/Component/DependencyInjection/Definition.php

@@ -29,6 +29,7 @@ class Definition
     private $deprecationTemplate = 'The "%service_id%" service is deprecated. You should stop using it, as it will soon be removed.';
     private $properties = array();
     private $calls = array();
+    private $getters = array();
     private $configurator;
     private $tags = array();
     private $public = true;
@@ -323,6 +324,37 @@ public function getMethodCalls()
         return $this->calls;
     }
 
+    /**
+     * @experimental in version 3.3
+     */
+    public function setOverriddenGetter($name, $returnValue)
+    {
+        if (!$name) {
+            throw new InvalidArgumentException(sprintf('Getter name cannot be empty.'));
+        }
+        $this->getters[strtolower($name)] = $returnValue;
+
+        return $this;
+    }
+
+    /**
+     * @experimental in version 3.3
+     */
+    public function setOverriddenGetters(array $getters)
+    {
+        $this->getters = array_change_key_case($getters, CASE_LOWER);
+
+        return $this;
+    }
+
+    /**
+     * @experimental in version 3.3
+     */
+    public function getOverriddenGetters()
+    {
+        return $this->getters;
+    }
+
     /**
      * Sets tags for this definition.
      *

src/Symfony/Component/DependencyInjection/Dumper/GraphvizDumper.php

@@ -80,6 +80,13 @@ public function dump(array $options = array())
                     $this->findEdges($id, $call[1], false, $call[0].'()')
                 );
             }
+
+            foreach ($definition->getOverriddenGetters() as $name => $value) {
+                $this->edges[$id] = array_merge(
+                    $this->edges[$id],
+                    $this->findEdges($id, $value, false, $name.'()')
+                );
+            }
         }
 
         return $this->container->resolveEnvPlaceholders($this->startDot().$this->addNodes().$this->addEdges().$this->endDot(), '__ENV_%s__');