feat!: allow mapping to any type

Previously, the method `TreeMapper::map` would allow mapping only to an
object. It is now possible to map to any type handled by the library.

It is for instance possible to map to an array of objects:

```php
$objects = (new \CuyZ\Valinor\MapperBuilder())->mapper()->map(
    'array<' . SomeClass::class . '>',
    [/* … */]
);
```

For simple use-cases, an array shape can be used:

```php
$array = (new \CuyZ\Valinor\MapperBuilder())->mapper()->map(
    'array{foo: string, bar: int}',
    [/* … */]
);

echo strtolower($array['foo']);
echo $array['bar'] * 2;
```

This new feature changes the possible behaviour of the mapper, meaning
static analysis tools need help to understand the types correctly. An
extension for PHPStan and a plugin for Psalm are now provided and can be
included in a project to automatically increase the type coverage.

.php-cs-fixer.dist.php

@@ -2,7 +2,8 @@
 
 $finder = PhpCsFixer\Finder::create()->in([
     './src',
-    './tests'
+    './tests',
+    './qa',
 ]);
 
 if (PHP_VERSION_ID < 8_00_00) {

README.md

@@ -125,6 +125,44 @@ public function getThread(int $id): Thread
 }
 ```
 
+### Mapping advanced types
+
+Although it is recommended to map an input to a value object, in some cases 
+mapping to another type can be easier/more flexible.
+
+It is for instance possible to map to an array of objects:
+
+```php
+try {
+    $objects = (new \CuyZ\Valinor\MapperBuilder())
+        ->mapper()
+        ->map(
+            'array<' . SomeClass::class . '>',
+            [/* … */]
+        );
+} catch (\CuyZ\Valinor\Mapper\MappingError $error) {
+    // Do something…
+}
+```
+
+For simple use-cases, an array shape can be used:
+
+```php
+try {
+    $array = (new \CuyZ\Valinor\MapperBuilder())
+        ->mapper()
+        ->map(
+            'array{foo: string, bar: int}',
+            [/* … */]
+        );
+
+    echo $array['foo'];
+    echo $array['bar'] * 2;
+} catch (\CuyZ\Valinor\Mapper\MappingError $error) {
+    // Do something…
+}
+```
+
 ### Validation
 
 The source given to a mapper can never be trusted, this is actually the very
@@ -225,7 +263,7 @@ map(new \CuyZ\Valinor\Mapper\Source\FileSource(
 ### Construction strategy
 
 During the mapping, instances of the objects are created and hydrated with the
-correct values. construction strategies will determine what values are needed
+correct values. Construction strategies will determine what values are needed
 and how an object is built.
 
 An object can provide either…
@@ -370,6 +408,91 @@ final class SomeClass
 }
 ```
 
+## Static analysis
+
+To help static analysis of a codebase using this library, an extension for
+[PHPStan] and a plugin for [Psalm] are provided. They enable these tools to
+better understand the behaviour of the mapper.
+
+Considering at least one of those tools are installed on a project, below are
+examples of the kind of errors that would be reported.
+
+**Mapping to an array of classes**
+
+```php
+final class SomeClass
+{
+    public function __construct(
+        public readonly string $foo,
+        public readonly int $bar,
+    ) {}
+}
+
+$objects = (new \CuyZ\Valinor\MapperBuilder())
+    ->mapper()
+    ->map(
+        'array<' . SomeClass::class . '>',
+        [/* … */]
+    );
+
+foreach ($objects as $object) {
+    // ✅
+    echo $object->foo;
+
+    // ✅
+    echo $object->bar * 2;
+
+    // ❌ Cannot perform operation between `string` and `int`
+    echo $object->foo * $object->bar;
+
+    // ❌ Property `SomeClass::$fiz` is not defined
+    echo $object->fiz;
+} 
+```
+
+**Mapping to a shaped array**
+
+```php
+$array = (new \CuyZ\Valinor\MapperBuilder())
+    ->mapper()
+    ->map(
+        'array{foo: string, bar: int}',
+        [/* … */]
+    );
+
+// ✅
+echo $array['foo'];
+
+// ❌ Expected `string` but got `int`
+echo strtolower($array['bar']);
+
+// ❌ Cannot perform operation between `string` and `int`
+echo $array['foo'] * $array['bar'];
+
+// ❌ Offset `fiz` does not exist on array
+echo $array['fiz']; 
+```
+
+---
+
+To activate this feature, the configuration must be updated for the installed
+tool(s):
+
+**PHPStan**
+
+```yaml
+includes:
+    - vendor/cuyz/valinor/qa/PHPStan/valinor-phpstan-configuration.php
+```
+
+**Psalm**
+
+```xml
+<plugins>
+    <plugin filename="vendor/cuyz/valinor/qa/Psalm/Plugin/TreeMapperPsalmPlugin.php"/>
+</plugins>
+```
+
 [PHPStan]: https://phpstan.org/
 
 [Psalm]: https://psalm.dev/

composer.json

@@ -36,7 +36,8 @@
     },
     "autoload-dev": {
         "psr-4": {
-            "CuyZ\\Valinor\\Tests\\": "tests"
+            "CuyZ\\Valinor\\Tests\\": "tests",
+            "CuyZ\\Valinor\\QA\\": "qa"
         }
     },
     "scripts": {

phpstan.neon.dist

@@ -1,11 +1,13 @@
 includes:
+    - qa/PHPStan/valinor-phpstan-configuration.php
     - vendor/phpstan/phpstan-strict-rules/rules.neon
 
 parameters:
     level: max
     paths:
         - src
         - tests
+        - qa/PHPStan
     ignoreErrors:
         # \PHPStan\Rules\BooleansInConditions
         - '#Only booleans are allowed in .* given#'
@@ -15,6 +17,10 @@ parameters:
         - '#Construct empty\(\) is not allowed\. Use more strict comparison\.#'
 
         - '#Method [\w\\:]+_data_provider\(\) return type has no value type specified in iterable type#'
+
+        - message: '#Template type T of method CuyZ\\Valinor\\Mapper\\TreeMapper::map\(\) is not referenced in a parameter#'
+          path: src/Mapper/TreeMapper.php
+
     stubFiles:
-        - stubs/Psr/SimpleCache/CacheInterface.stub
+        - qa/PHPStan/Stubs/Psr/SimpleCache/CacheInterface.stub
     tmpDir: var/cache/phpstan

qa/PHPStan/Extension/TreeMapperPHPStanExtension.php

@@ -0,0 +1,62 @@
+<?php
+
+declare(strict_types=1);
+
+namespace CuyZ\Valinor\QA\PHPStan\Extension;
+
+use CuyZ\Valinor\Mapper\TreeMapper;
+use PhpParser\Node\Expr\MethodCall;
+use PHPStan\Analyser\Scope;
+use PHPStan\PhpDoc\TypeStringResolver;
+use PHPStan\Reflection\MethodReflection;
+use PHPStan\Type\Constant\ConstantStringType;
+use PHPStan\Type\DynamicMethodReturnTypeExtension;
+use PHPStan\Type\Generic\GenericClassStringType;
+use PHPStan\Type\MixedType;
+use PHPStan\Type\Type;
+use PHPStan\Type\UnionType;
+
+final class TreeMapperPHPStanExtension implements DynamicMethodReturnTypeExtension
+{
+    private TypeStringResolver $resolver;
+
+    public function __construct(TypeStringResolver $resolver)
+    {
+        $this->resolver = $resolver;
+    }
+
+    public function getClass(): string
+    {
+        return TreeMapper::class;
+    }
+
+    public function isMethodSupported(MethodReflection $methodReflection): bool
+    {
+        return $methodReflection->getName() === 'map';
+    }
+
+    public function getTypeFromMethodCall(MethodReflection $methodReflection, MethodCall $methodCall, Scope $scope): Type
+    {
+        $argument = $methodCall->getArgs()[0]->value;
+        $type = $scope->getType($argument);
+
+        if ($type instanceof UnionType) {
+            return $type->traverse(fn (Type $type) => $this->type($type));
+        }
+
+        return $this->type($type);
+    }
+
+    private function type(Type $type): Type
+    {
+        if ($type instanceof GenericClassStringType) {
+            return $type->getGenericType();
+        }
+
+        if ($type instanceof ConstantStringType) {
+            return $this->resolver->resolve($type->getValue());
+        }
+
+        return new MixedType();
+    }
+}

qa/PHPStan/valinor-phpstan-configuration.php

@@ -0,0 +1,14 @@
+<?php
+
+use CuyZ\Valinor\QA\PHPStan\Extension\TreeMapperPHPStanExtension;
+
+require_once 'Extension/TreeMapperPHPStanExtension.php';
+
+return [
+    'services' => [
+        [
+            'class' => TreeMapperPHPStanExtension::class,
+            'tags' => ['phpstan.broker.dynamicMethodReturnTypeExtension']
+        ]
+    ],
+];

qa/Psalm/Plugin/TreeMapperPsalmPlugin.php

@@ -0,0 +1,68 @@
+<?php
+
+declare(strict_types=1);
+
+namespace CuyZ\Valinor\QA\Psalm\Plugin;
+
+use CuyZ\Valinor\Mapper\TreeMapper;
+use Psalm\Plugin\EventHandler\Event\MethodReturnTypeProviderEvent;
+use Psalm\Plugin\EventHandler\MethodReturnTypeProviderInterface;
+use Psalm\Type;
+use Psalm\Type\Atomic;
+use Psalm\Type\Atomic\TClassString;
+use Psalm\Type\Atomic\TDependentGetClass;
+use Psalm\Type\Atomic\TLiteralString;
+use Psalm\Type\Union;
+
+final class TreeMapperPsalmPlugin implements MethodReturnTypeProviderInterface
+{
+    public static function getClassLikeNames(): array
+    {
+        return [TreeMapper::class];
+    }
+
+    public static function getMethodReturnType(MethodReturnTypeProviderEvent $event): ?Union
+    {
+        if ($event->getMethodNameLowercase() !== 'map') {
+            return null;
+        }
+
+        $type = $event->getSource()->getNodeTypeProvider()->getType($event->getCallArgs()[0]->value);
+
+        if (! $type) {
+            return null;
+        }
+
+        $types = [];
+
+        foreach ($type->getChildNodes() as $node) {
+            $inferred = self::type($node);
+
+            if ($inferred === null) {
+                return null;
+            }
+
+            $types[] = $inferred;
+        }
+
+        if (count($types) === 0) {
+            return null;
+        }
+
+        return Type::combineUnionTypeArray($types, $event->getSource()->getCodebase());
+    }
+
+    private static function type(Atomic $node): ?Union
+    {
+        switch (true) {
+            case $node instanceof TLiteralString:
+                return Type::parseString($node->value);
+            case $node instanceof TDependentGetClass:
+                return $node->as_type;
+            case $node instanceof TClassString && $node->as_type:
+                return new Union([$node->as_type]);
+            default:
+                return null;
+        }
+    }
+}

src/Mapper/MappingError.php

@@ -16,7 +16,7 @@ public function __construct(Node $node)
         $this->node = $node;
 
         parent::__construct(
-            "Could not map an object of type `{$node->type()}` with the given source.",
+            "Could not map type `{$node->type()}` with the given source.",
             1617193185
         );
     }

src/Mapper/TreeMapper.php

@@ -9,11 +9,11 @@ interface TreeMapper
     /**
      * @template T of object
      *
-     * @param class-string<T> $signature
+     * @param string|class-string<T> $signature
      * @param mixed $source
-     * @return T
+     * @return T|mixed
      *
      * @throws MappingError
      */
-    public function map(string $signature, $source): object;
+    public function map(string $signature, $source);
 }