Provide a dynamic return type for EntityTypeManager::getStorage

Fixes #6

Author: mglaman

README.md

@@ -17,7 +17,9 @@ includes:
 
 ## Enabling rules one-by-one
 
-If you don't want to start using all the available strict rules at once but only one or two, you can! Just don't include the whole `rules.neon` from this package in your configuration, but look at its contents and copy only the rules you want to your configuration under the `services` key:
+If you don't want to start using all the available strict rules at once but only one or two, you can! Just don't include 
+the whole `rules.neon` from this package in your configuration, but look at its contents and copy only the rules you 
+want to your configuration under the `services` key:
 
 ```
 services:
@@ -37,3 +39,29 @@ parameters:
 		- *Test.php
 		- *TestBase.php
 ```
+
+## Adapting to your project
+
+### Entity storage mappings.
+
+The `EntityTypeManagerGetStorageDynamicReturnTypeExtension` service helps map dynamic return types. This inspects the 
+passed entity type ID and tries to return a known storage class, besides the default `EntityStorageInterface`. The
+default mapping can be found in `extension.neon`. For example:
+
+```
+drupal:
+	entityTypeStorageMapping:
+		node: Drupal\node\NodeStorage
+		taxonomy_term: Drupal\taxonomy\TermStorage
+		user: Drupal\user\UserStorage
+```
+
+To add support for custom entities, you may add the same definition in your project's `phpstan.neon`. See the following
+example for adding a mapping for Search API:
+
+```
+drupal:
+	entityTypeStorageMapping:
+		search_api_index: Drupal\search_api\Entity\SearchApiConfigEntityStorage
+		search_api_server: Drupal\search_api\Entity\SearchApiConfigEntityStorage
+```

extension.neon

@@ -8,8 +8,19 @@ parameters:
 		- inc
 extensions:
 	drupal: PHPStan\DependencyInjection\DrupalExtension
+drupal:
+	entityTypeStorageMapping:
+		node: Drupal\node\NodeStorage
+		taxonomy_term: Drupal\taxonomy\TermStorage
+		user: Drupal\user\UserStorage
 rules:
 	- PHPStan\Rules\Classes\PluginManagerInspectionRule
 	- PHPStan\Rules\Drupal\Coder\DiscouragedFunctionsRule
 	- PHPStan\Rules\Drupal\GlobalDrupalDependencyInjectionRule
 	- PHPStan\Rules\Drupal\PluginManager\PluginManagerSetsCacheBackendRule
+services:
+	-
+		class: PHPStan\Type\EntityTypeManagerGetStorageDynamicReturnTypeExtension
+		arguments:
+			entityTypeStorageMapping: %drupal.entityTypeStorageMapping%
+		tags: [phpstan.broker.dynamicMethodReturnTypeExtension]

src/DependencyInjection/DrupalExtension.php

@@ -80,6 +80,8 @@ public function loadConfiguration(): void
         $this->modules = $config['modules'] ?? [];
         $this->themes = $config['themes'] ?? [];
 
+        $builder->parameters['drupal']['entityTypeStorageMapping'] = $config['entityTypeStorageMapping'];
+
         $builder = $this->getContainerBuilder();
         foreach ($builder->getDefinitions() as $definition) {
             $factory = $definition->getFactory();

src/Type/EntityTypeManagerGetStorageDynamicReturnTypeExtension.php

@@ -0,0 +1,67 @@
+<?php declare(strict_types=1);
+
+namespace PHPStan\Type;
+
+use PhpParser\Node\Expr\BinaryOp\Concat;
+use PhpParser\Node\Expr\MethodCall;
+use PhpParser\Node\Scalar\String_;
+use PHPStan\Analyser\Scope;
+use PHPStan\Reflection\MethodReflection;
+use PHPStan\Reflection\ParametersAcceptorSelector;
+
+class EntityTypeManagerGetStorageDynamicReturnTypeExtension implements DynamicMethodReturnTypeExtension
+{
+    /**
+     * @var array
+     */
+    private $entityTypeStorageMapping;
+
+    public function __construct(array $entityTypeStorageMapping = [])
+    {
+        $this->entityTypeStorageMapping = $entityTypeStorageMapping;
+    }
+
+    public function getClass(): string
+    {
+        return 'Drupal\Core\Entity\EntityTypeManagerInterface';
+    }
+
+    public function isMethodSupported(MethodReflection $methodReflection): bool
+    {
+        return $methodReflection->getName() === 'getStorage';
+    }
+
+    public function getTypeFromMethodCall(
+        MethodReflection $methodReflection,
+        MethodCall $methodCall,
+        Scope $scope
+    ): Type {
+        $returnType = ParametersAcceptorSelector::selectSingle($methodReflection->getVariants())->getReturnType();
+        if (!isset($methodCall->args[0])) {
+            return $returnType;
+        }
+
+        $arg1 = $methodCall->args[0]->value;
+
+        // @todo handle where the first param is EntityTypeInterface::id()
+        if ($arg1 instanceof MethodCall) {
+            // There may not be much that can be done, since it's a generic EntityTypeInterface.
+            return $returnType;
+        }
+        // @todo handle concat ie: entity_{$display_context}_display for entity_form_display or entity_view_display
+        if ($arg1 instanceof Concat) {
+            return $returnType;
+        }
+        if (!$arg1 instanceof String_) {
+            // @todo determine what these types are, and try to resolve entity name from.
+            return $returnType;
+        }
+
+        $entityTypeId = $arg1->value;
+
+        if (isset($this->entityTypeStorageMapping[$entityTypeId])) {
+            return new ObjectType($this->entityTypeStorageMapping[$entityTypeId]);
+        }
+        return $returnType;
+    }
+}