RemoveUnusedPrivateMethodRector.php

<?php

declare(strict_types=1);

namespace Rector\DeadCode\Rector\ClassMethod;

use PhpParser\Node;
use PhpParser\Node\Expr\ClassConstFetch;
use PhpParser\Node\Expr\MethodCall;
use PhpParser\Node\Expr\StaticCall;
use PhpParser\Node\Expr\Variable;
use PhpParser\Node\Identifier;
use PhpParser\Node\Stmt\Class_;
use PhpParser\Node\Stmt\ClassMethod;
use PHPStan\Reflection\ClassReflection;
use Rector\DeadCode\NodeAnalyzer\IsClassMethodUsedAnalyzer;
use Rector\PhpParser\Node\BetterNodeFinder;
use Rector\PHPStan\ScopeFetcher;
use Rector\Rector\AbstractRector;
use Rector\Reflection\ReflectionResolver;
use Rector\TypeDeclarationDocblocks\NodeFinder\DataProviderMethodsFinder;
use Rector\ValueObject\MethodName;
use Symplify\RuleDocGenerator\ValueObject\CodeSample\CodeSample;
use Symplify\RuleDocGenerator\ValueObject\RuleDefinition;

/**
 * @see \Rector\Tests\DeadCode\Rector\ClassMethod\RemoveUnusedPrivateMethodRector\RemoveUnusedPrivateMethodRectorTest
 */
final class RemoveUnusedPrivateMethodRector extends AbstractRector
{
    public function __construct(
        private readonly IsClassMethodUsedAnalyzer $isClassMethodUsedAnalyzer,
        private readonly ReflectionResolver $reflectionResolver,
        private readonly BetterNodeFinder $betterNodeFinder,
        private readonly DataProviderMethodsFinder $dataProviderMethodsFinder
    ) {
    }

    public function getRuleDefinition(): RuleDefinition
    {
        return new RuleDefinition('Remove unused private method', [
            new CodeSample(
                <<<'CODE_SAMPLE'
final class SomeController
{
    public function run()
    {
        return 5;
    }

    private function skip()
    {
        return 10;
    }
}
CODE_SAMPLE
                ,
                <<<'CODE_SAMPLE'
final class SomeController
{
    public function run()
    {
        return 5;
    }
}
CODE_SAMPLE
            ),
        ]);
    }

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

    /**
     * @param Class_ $node
     */
    public function refactor(Node $node): ?Node
    {
        // unreliable to detect on anonymous class: doesn't make sense
        if ($node->isAnonymous()) {
            return null;
        }

        if (! $this->hasPrivateMethod($node)) {
            return null;
        }

        $hasChanged = false;

        $classReflection = $this->reflectionResolver->resolveClassReflection($node);
        if (! $classReflection instanceof ClassReflection) {
            return null;
        }

        $dataProviderMethodNames = $this->resolveDataProviderMethodNames($node);

        // methods invoked via a class-string static call, e.g. self::class::sampleClass(),
        // are not seen by the usage analyzer
        $classStringCallMethodNames = $this->resolveClassStringStaticCallNames($node);

        foreach ($node->stmts as $classStmtKey => $classStmt) {
            if (! $classStmt instanceof ClassMethod) {
                continue;
            }

            if (! $classStmt->isPrivate()) {
                continue;
            }

            $classMethod = $classStmt;
            if ($this->hasDynamicMethodCallOnFetchThis($classStmt)) {
                continue;
            }

            $scope = ScopeFetcher::fetch($node);
            if ($this->shouldSkip($classStmt, $classReflection)) {
                continue;
            }

            if ($this->isClassMethodUsedAnalyzer->isClassMethodUsed($node, $classStmt, $scope)) {
                continue;
            }

            if ($this->isNames($classMethod, $dataProviderMethodNames)) {
                continue;
            }

            if ($this->isNames($classMethod, $classStringCallMethodNames)) {
                continue;
            }

            unset($node->stmts[$classStmtKey]);
            $hasChanged = true;
        }

        if ($hasChanged) {
            return $node;
        }

        return null;
    }

    private function hasPrivateMethod(Class_ $class): bool
    {
        return array_any($class->getMethods(), fn(ClassMethod $classMethod): bool => $classMethod->isPrivate());
    }

    private function shouldSkip(ClassMethod $classMethod, ClassReflection $classReflection): bool
    {
        // unreliable to detect trait, interface: doesn't make sense
        if ($classReflection->isTrait()) {
            return true;
        }

        if ($classReflection->isInterface()) {
            return true;
        }

        // skip magic methods - @see https://www.php.net/manual/en/language.oop5.magic.php
        if ($classMethod->isMagic()) {
            return true;
        }

        return $classReflection->hasMethod(MethodName::CALL);
    }

    /**
     * Mirrors PHPStan's UnusedPrivateMethodRule fix for class-string static calls
     * @see https://github.com/phpstan/phpstan-src/pull/5953
     *
     * @return string[]
     */
    private function resolveClassStringStaticCallNames(Class_ $class): array
    {
        $methodNames = [];

        /** @var StaticCall[] $staticCalls */
        $staticCalls = $this->betterNodeFinder->findInstanceOf($class->stmts, StaticCall::class);
        foreach ($staticCalls as $staticCall) {
            // e.g. self::class::sampleClass() - the called class is a ::class expression
            if (! $staticCall->class instanceof ClassConstFetch) {
                continue;
            }

            if (! $this->isName($staticCall->class->name, 'class')) {
                continue;
            }

            if (! $staticCall->name instanceof Identifier) {
                continue;
            }

            $methodNames[] = $staticCall->name->toString();
        }

        return $methodNames;
    }

    private function hasDynamicMethodCallOnFetchThis(ClassMethod $classMethod): bool
    {
        return (bool) $this->betterNodeFinder->findFirst(
            (array) $classMethod->stmts,
            function (Node $subNode): bool {
                if (! $subNode instanceof MethodCall) {
                    return false;
                }

                if (! $subNode->var instanceof Variable) {
                    return false;
                }

                if (! $this->isName($subNode->var, 'this')) {
                    return false;
                }

                return $subNode->name instanceof Variable;
            }
        );
    }

    /**
     * @return string[]
     */
    private function resolveDataProviderMethodNames(Class_ $class): array
    {
        $dataProviderClassMethods = $this->dataProviderMethodsFinder->findDataProviderNodesInClass($class);
        return $this->nodeNameResolver->getNames($dataProviderClassMethods);
    }
}