Introduce get_post_types dynamic return service

Account for different results from `get_post_types` based on the
arguments passed.

Also submitted a pull request upstream and simply keeping this here in
case that does not get merged.

@todo Remove this extension if the pull request gets merged and released upstream

szepeviktor/phpstan-wordpress#177

Author: lipemat

.idea/phpstan.iml

@@ -1,3 +1,8 @@
+services:
+  - class: Lipe\Lib\Phpstan\Services\GetPostTypesDynamicFunctionReturnTypeExtension
+    tags:
+      - phpstan.broker.dynamicFunctionReturnTypeExtension
+
 parameters:
   dynamicConstantNames:
     - COOKIEPATH

extension.neon

@@ -0,0 +1,57 @@
+<?php
+declare( strict_types=1 );
+
+namespace Lipe\Lib\Phpstan\Services;
+
+use PhpParser\Node\Expr\FuncCall;
+use PHPStan\Analyser\Scope;
+use PHPStan\Reflection\FunctionReflection;
+use PHPStan\Type\ArrayType;
+use PHPStan\Type\DynamicFunctionReturnTypeExtension;
+use PHPStan\Type\IntegerType;
+use PHPStan\Type\ObjectType;
+use PHPStan\Type\StringType;
+use PHPStan\Type\Type;
+
+/**
+ * The `get_post_types` function returns different results based on the
+ * arguments passed to the function.
+ *
+ * @author Mat Lipe
+ * @since  2.6.0
+ *
+ * @todo   Remove this extension if the pull request gets merged and released upstream
+ *
+ * @link   https://github.com/szepeviktor/phpstan-wordpress/pull/177
+ * @link   https://phpstan.org/developing-extensions/dynamic-return-type-extensions
+ *
+ */
+class GetPostTypesDynamicFunctionReturnTypeExtension implements DynamicFunctionReturnTypeExtension {
+	public function isFunctionSupported( FunctionReflection $functionReflection ) : bool {
+		return $functionReflection->getName() === 'get_post_types';
+	}
+
+
+	/**
+	 * - Return `string[]` if default or `$output = 'names'`.
+	 * - Return `WP_Post_Type[]` if `$output` is anything but 'names';
+	 *
+	 * @link https://developer.wordpress.org/reference/functions/get_post_types/#parameters
+	 */
+	public function getTypeFromFunctionCall( FunctionReflection $functionReflection, FuncCall $functionCall, Scope $scope ) : ?Type {
+		$args = $functionCall->getArgs();
+
+		if ( count( $args ) < 2 ) {
+			return new ArrayType( new IntegerType(), new StringType() );
+		}
+
+		$argumentType = $scope->getType( $args[1]->value );
+		if ( count( $argumentType->getConstantStrings() ) === 1 ) {
+			if ( 'names' === $argumentType->getConstantStrings()[0]->getValue() ) {
+				return new ArrayType( new IntegerType(), new StringType() );
+			}
+		}
+
+		return new ArrayType( new IntegerType(), new ObjectType( 'WP_Post_Type' ) );
+	}
+}