SimplifyUselessVariableRector.php

<?php

declare(strict_types=1);

namespace Rector\CodeQuality\Rector\FunctionLike;

use PhpParser\Comment\Doc;
use PhpParser\Node;
use PhpParser\Node\Expr\Assign;
use PhpParser\Node\Expr\Variable;
use PhpParser\Node\Stmt;
use PhpParser\Node\Stmt\Expression;
use PhpParser\Node\Stmt\Return_;
use PHPStan\Type\MixedType;
use Rector\BetterPhpDocParser\PhpDocInfo\PhpDocInfoFactory;
use Rector\NodeAnalyzer\CallAnalyzer;
use Rector\NodeAnalyzer\VariableAnalyzer;
use Rector\NodeTypeResolver\Node\AttributeKey;
use Rector\PhpParser\Enum\NodeGroup;
use Rector\Rector\AbstractRector;
use Rector\RuleDoc\CodeSample\CodeSample;
use Rector\RuleDoc\RuleDefinition;

/**
 * @see \Rector\Tests\CodeQuality\Rector\FunctionLike\SimplifyUselessVariableRector\SimplifyUselessVariableRectorTest
 */
final class SimplifyUselessVariableRector extends AbstractRector
{
    public function __construct(
        private readonly VariableAnalyzer $variableAnalyzer,
        private readonly CallAnalyzer $callAnalyzer,
        private readonly PhpDocInfoFactory $phpDocInfoFactory
    ) {
    }

    public function getRuleDefinition(): RuleDefinition
    {
        return new RuleDefinition('Remove useless variable assigns', [
            new CodeSample(
                <<<'CODE_SAMPLE'
function () {
    $a = true;
    return $a;
};
CODE_SAMPLE
                ,
                <<<'CODE_SAMPLE'
function () {
    return true;
};
CODE_SAMPLE
            ),
        ]);
    }

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

    /**
     * @param StmtsAware $node
     */
    public function refactor(Node $node): ?Node
    {
        $stmts = $node->stmts;
        if ($stmts === null) {
            return null;
        }

        foreach ($stmts as $key => $stmt) {
            // has previous node?
            if (! isset($stmts[$key - 1])) {
                continue;
            }

            if (! $stmt instanceof Return_) {
                continue;
            }

            $previousStmt = $stmts[$key - 1];
            if ($this->shouldSkipStmt($stmt, $previousStmt)) {
                return null;
            }

            if ($this->hasSomeComment($previousStmt)) {
                return null;
            }

            // the variable might be used in commented-out code between assign and return
            if ($this->isVariableMentionedInComment($stmt)) {
                return null;
            }

            if ($this->isReturnWithVarAnnotation($stmt)) {
                return null;
            }

            if (! $previousStmt instanceof Expression) {
                return null;
            }

            $assign = $previousStmt->expr;
            if (! $assign instanceof Assign) {
                return null;
            }

            $stmt->expr = $assign->expr;
            unset($node->stmts[$key - 1]);

            return $node;
        }

        return null;
    }

    private function shouldSkipStmt(Return_ $return, Stmt $previousStmt): bool
    {
        if (! $return->expr instanceof Variable) {
            return true;
        }

        if ($return->getAttribute(AttributeKey::IS_INSIDE_BYREF_FUNCTION_LIKE) === true) {
            return true;
        }

        if (! $previousStmt instanceof Expression) {
            return true;
        }

        // is variable part of single assign
        $previousNode = $previousStmt->expr;

        if (! $previousNode instanceof Assign) {
            return true;
        }

        $variable = $return->expr;
        // is the same variable
        if (! $this->nodeComparator->areNodesEqual($previousNode->var, $variable)) {
            return true;
        }

        if ($this->variableAnalyzer->isStaticOrGlobal($variable)) {
            return true;
        }

        /** @var Variable $previousVar */
        $previousVar = $previousNode->var;
        if ($this->callAnalyzer->isNewInstance($previousVar)) {
            return true;
        }

        return $this->variableAnalyzer->isUsedByReference($variable);
    }

    private function isVariableMentionedInComment(Return_ $return): bool
    {
        $comments = $return->getComments();
        if ($comments === []) {
            return false;
        }

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

        $variableName = $return->expr->name;
        if (! is_string($variableName)) {
            return false;
        }

        return array_any($comments, fn ($comment): bool => str_contains($comment->getText(), '$' . $variableName));
    }

    private function hasSomeComment(Stmt $stmt): bool
    {
        if ($stmt->getComments() !== []) {
            return true;
        }

        return $stmt->getDocComment() instanceof Doc;
    }

    private function isReturnWithVarAnnotation(Return_ $return): bool
    {
        $phpDocInfo = $this->phpDocInfoFactory->createFromNodeOrEmpty($return);
        return ! $phpDocInfo->getVarType() instanceof MixedType;
    }
}