InnerFunctionToPrivateMethodRector.php

<?php

declare(strict_types=1);

namespace Rector\CodeQuality\Rector\Class_;

use PhpParser\Modifiers;
use PhpParser\Node;
use PhpParser\Node\Expr\FuncCall;
use PhpParser\Node\Expr\MethodCall;
use PhpParser\Node\Expr\StaticCall;
use PhpParser\Node\Expr\Variable;
use PhpParser\Node\Name;
use PhpParser\Node\Scalar\String_;
use PhpParser\Node\Stmt\Class_;
use PhpParser\Node\Stmt\ClassMethod;
use PhpParser\Node\Stmt\Function_;
use Rector\Rector\AbstractRector;
use Symplify\RuleDocGenerator\ValueObject\CodeSample\CodeSample;
use Symplify\RuleDocGenerator\ValueObject\RuleDefinition;

/**
 * @see \Rector\Tests\CodeQuality\Rector\Class_\InnerFunctionToPrivateMethodRector\InnerFunctionToPrivateMethodRectorTest
 */
final class InnerFunctionToPrivateMethodRector extends AbstractRector
{
    public function getRuleDefinition(): RuleDefinition
    {
        return new RuleDefinition(
            'Turn an inner named function declared inside a class method into a private method, as inner named functions are not supported by PHPStan',
            [
                new CodeSample(
                    <<<'CODE_SAMPLE'
class SomeClass
{
    public function run(): void
    {
        function inner(): void
        {
            echo 'hello';
        }

        inner();
    }
}
CODE_SAMPLE
                    ,
                    <<<'CODE_SAMPLE'
class SomeClass
{
    public function run(): void
    {
        $this->inner();
    }

    private function inner(): void
    {
        echo 'hello';
    }
}
CODE_SAMPLE
                ),
            ]
        );
    }

    /**
     * @return array<class-string<Node>>
     */
    public function getNodeTypes(): array
    {
        return [Class_::class];
    }

    /**
     * @param Class_ $node
     */
    public function refactor(Node $node): ?Node
    {
        $existingMethodNames = array_map(
            fn (ClassMethod $classMethod): string => $classMethod->name->toString(),
            $node->getMethods()
        );

        $newClassMethods = [];

        foreach ($node->getMethods() as $classMethod) {
            $innerFunctions = $this->extractInnerFunctions($classMethod, $existingMethodNames);
            if ($innerFunctions === []) {
                continue;
            }

            $isStatic = $classMethod->isStatic();
            $innerFunctionNames = array_map(
                fn (Function_ $innerFunction): string => $innerFunction->name->toString(),
                $innerFunctions
            );

            foreach ($innerFunctions as $innerFunction) {
                $newClassMethod = $this->createPrivateMethod($innerFunction, $isStatic);
                $this->rewriteCallsToMethod($newClassMethod, $innerFunctionNames, $isStatic);
                $newClassMethods[] = $newClassMethod;
            }

            $this->rewriteCallsToMethod($classMethod, $innerFunctionNames, $isStatic);
        }

        if ($newClassMethods === []) {
            return null;
        }

        $node->stmts = array_merge($node->stmts, $newClassMethods);

        return $node;
    }

    /**
     * @param string[] $existingMethodNames
     * @return Function_[]
     */
    private function extractInnerFunctions(ClassMethod $classMethod, array &$existingMethodNames): array
    {
        $innerFunctions = [];

        foreach ($classMethod->stmts ?? [] as $key => $stmt) {
            if (! $stmt instanceof Function_) {
                continue;
            }

            $functionName = $stmt->name->toString();

            // avoid collision with an already existing method
            if (in_array($functionName, $existingMethodNames, true)) {
                continue;
            }

            // avoid breaking string callables, e.g. usort($items, 'functionName')
            if ($this->isReferencedAsStringCallable($classMethod, $functionName)) {
                continue;
            }

            $existingMethodNames[] = $functionName;
            $innerFunctions[] = $stmt;
            unset($classMethod->stmts[$key]);
        }

        if ($innerFunctions !== []) {
            $classMethod->stmts = array_values((array) $classMethod->stmts);
        }

        return $innerFunctions;
    }

    private function isReferencedAsStringCallable(ClassMethod $classMethod, string $functionName): bool
    {
        $isReferenced = false;

        $this->traverseNodesWithCallable($classMethod->stmts ?? [], function (Node $node) use (
            $functionName,
            &$isReferenced
        ): null {
            if ($node instanceof String_ && $node->value === $functionName) {
                $isReferenced = true;
            }

            return null;
        });

        return $isReferenced;
    }

    private function createPrivateMethod(Function_ $innerFunction, bool $isStatic): ClassMethod
    {
        $flags = Modifiers::PRIVATE;
        if ($isStatic) {
            $flags |= Modifiers::STATIC;
        }

        $classMethod = new ClassMethod($innerFunction->name, [
            'flags' => $flags,
            'byRef' => $innerFunction->byRef,
            'params' => $innerFunction->params,
            'returnType' => $innerFunction->returnType,
            'stmts' => $innerFunction->stmts,
            'attrGroups' => $innerFunction->attrGroups,
        ]);

        $this->mirrorComments($classMethod, $innerFunction);

        return $classMethod;
    }

    /**
     * @param string[] $innerFunctionNames
     */
    private function rewriteCallsToMethod(ClassMethod $classMethod, array $innerFunctionNames, bool $isStatic): void
    {
        $this->traverseNodesWithCallable($classMethod->stmts ?? [], function (Node $node) use (
            $innerFunctionNames,
            $isStatic
        ): MethodCall|StaticCall|null {
            if (! $node instanceof FuncCall) {
                return null;
            }

            if (! $node->name instanceof Name) {
                return null;
            }

            $functionName = $node->name->toString();
            if (! in_array($functionName, $innerFunctionNames, true)) {
                return null;
            }

            if ($isStatic) {
                return new StaticCall(new Name('self'), $functionName, $node->args);
            }

            return new MethodCall(new Variable('this'), $functionName, $node->args);
        });
    }
}