Resolve nullable types using a Nullable type wrapper

src/TypeResolver.php

@@ -16,6 +16,7 @@
 use phpDocumentor\Reflection\Types\Compound;
 use phpDocumentor\Reflection\Types\Context;
 use phpDocumentor\Reflection\Types\Iterable_;
+use phpDocumentor\Reflection\Types\Nullable;
 use phpDocumentor\Reflection\Types\Object_;
 
 final class TypeResolver
@@ -102,6 +103,8 @@ public function resolve($type, Context $context = null)
         }
 
         switch (true) {
+            case $this->isNullableType($type):
+                return $this->resolveNullableType($type, $context);
             case $this->isKeyword($type):
                 return $this->resolveKeyword($type);
             case ($this->isCompoundType($type)):
@@ -208,6 +211,18 @@ private function isCompoundType($type)
         return strpos($type, '|') !== false;
     }
 
+    /**
+     * Test whether the given type is a nullable type (i.e. `?string`)
+     *
+     * @param string $type
+     *
+     * @return bool
+     */
+    private function isNullableType($type)
+    {
+        return $type[0] === '?';
+    }
+
     /**
      * Resolves the given typed array string (i.e. `string[]`) into an Array object with the right types set.
      *
@@ -265,4 +280,17 @@ private function resolveCompoundType($type, Context $context)
 
         return new Compound($types);
     }
+
+    /**
+     * Resolve nullable types (i.e. `?string`) into a Nullable type wrapper
+     *
+     * @param string $type
+     * @param Context $context
+     *
+     * @return Nullable
+     */
+    private function resolveNullableType($type, Context $context)
+    {
+        return new Nullable($this->resolve(ltrim($type, '?'), $context));
+    }
 }

src/Types/Nullable.php

@@ -0,0 +1,56 @@
+<?php
+/**
+ * This file is part of phpDocumentor.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ *
+ * @copyright 2010-2017 Mike van Riel<mike@phpdoc.org>
+ * @license   http://www.opensource.org/licenses/mit-license.php MIT
+ * @link      http://phpdoc.org
+ */
+
+namespace phpDocumentor\Reflection\Types;
+
+use phpDocumentor\Reflection\Type;
+
+/**
+ * Value Object representing a nullable type. The real type is wrapped.
+ */
+final class Nullable implements Type
+{
+    /**
+     * @var Type
+     */
+    private $realType;
+
+    /**
+     * Initialises this nullable type using the real type embedded
+     *
+     * @param Type $realType
+     */
+    public function __construct(Type $realType)
+    {
+        $this->realType = $realType;
+    }
+
+    /**
+     * Provide access to the actual type directly, if needed.
+     *
+     * @return Type
+     */
+    public function getActualType()
+    {
+        return $this->realType;
+    }
+
+    /**
+     * Returns a rendered output of the Type as it would be used in a DocBlock.
+     *
+     * @return string
+     */
+    public function __toString()
+    {
+        return '?' . $this->realType->__toString();
+    }
+}

tests/unit/TypeResolverTest.php

@@ -17,7 +17,9 @@
 use phpDocumentor\Reflection\Types\Compound;
 use phpDocumentor\Reflection\Types\Context;
 use phpDocumentor\Reflection\Types\Iterable_;
+use phpDocumentor\Reflection\Types\Nullable;
 use phpDocumentor\Reflection\Types\Object_;
+use phpDocumentor\Reflection\Types\String_;
 
 /**
  * @coversDefaultClass phpDocumentor\Reflection\TypeResolver
@@ -142,6 +144,27 @@ public function testResolvingTypedArrays()
         $this->assertInstanceOf('phpDocumentor\Reflection\Types\String_', $resolvedType->getValueType());
     }
 
+    /**
+     * @covers ::__construct
+     * @covers ::resolve
+     * @covers ::<private>
+     *
+     * @uses \phpDocumentor\Reflection\Types\Context
+     * @uses \phpDocumentor\Reflection\Types\Nullable
+     * @uses \phpDocumentor\Reflection\Types\String_
+     */
+    public function testResolvingNullableTypes()
+    {
+        $fixture = new TypeResolver();
+
+        /** @var Nullable $resolvedType */
+        $resolvedType = $fixture->resolve('?string', new Context(''));
+
+        $this->assertInstanceOf(Nullable::class, $resolvedType);
+        $this->assertInstanceOf(String_::class, $resolvedType->getActualType());
+        $this->assertSame('?string', (string)$resolvedType);
+    }
+
     /**
      * @covers ::__construct
      * @covers ::resolve

tests/unit/Types/NullableTest.php

@@ -0,0 +1,40 @@
+<?php
+/**
+ * This file is part of phpDocumentor.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ *
+ * @copyright 2010-2017 Mike van Riel<mike@phpdoc.org>
+ * @license   http://www.opensource.org/licenses/mit-license.php MIT
+ * @link      http://phpdoc.org
+ */
+
+namespace phpDocumentor\Reflection\Types;
+
+/**
+ * @coversDefaultClass \phpDocumentor\Reflection\Types\Nullable
+ */
+class NullableTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * @covers ::__construct
+     * @covers ::getActualType
+     */
+    public function testNullableTypeWrapsCorrectly()
+    {
+        $realType = new String_();
+
+        $nullableString = new Nullable($realType);
+
+        $this->assertSame($realType, $nullableString->getActualType());
+    }
+
+    /**
+     * @covers ::__toString
+     */
+    public function testNullableStringifyCorrectly()
+    {
+        $this->assertSame('?string', (string)(new Nullable(new String_())));
+    }
+}