RemoveDoubleAssignRector.php

<?php

declare(strict_types=1);

namespace Rector\DeadCode\Rector\Assign;

use PhpParser\Node;
use PhpParser\Node\Expr\Assign;
use PhpParser\Node\Expr\PropertyFetch;
use PhpParser\Node\Expr\StaticPropertyFetch;
use PhpParser\Node\Expr\Variable;
use PhpParser\Node\Stmt\Expression;
use PhpParser\Node\Stmt\TryCatch;
use Rector\DeadCode\SideEffect\SideEffectNodeDetector;
use Rector\PhpParser\Enum\NodeGroup;
use Rector\PhpParser\Node\BetterNodeFinder;
use Rector\Rector\AbstractRector;
use Symplify\RuleDocGenerator\ValueObject\CodeSample\CodeSample;
use Symplify\RuleDocGenerator\ValueObject\RuleDefinition;

/**
 * @see \Rector\Tests\DeadCode\Rector\Assign\RemoveDoubleAssignRector\RemoveDoubleAssignRectorTest
 */
final class RemoveDoubleAssignRector extends AbstractRector
{
    public function __construct(
        private readonly SideEffectNodeDetector $sideEffectNodeDetector,
        private readonly BetterNodeFinder $betterNodeFinder,
    ) {
    }

    public function getRuleDefinition(): RuleDefinition
    {
        return new RuleDefinition('Simplify useless double assigns', [
            new CodeSample(
                <<<'CODE_SAMPLE'
$value = 1;
$value = 1;
CODE_SAMPLE
                ,
                '$value = 1;'
            ),
        ]);
    }

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

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

        $hasChanged = false;

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

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

            $nextStmt = $node->stmts[$key + 1];
            if (! $nextStmt instanceof Expression) {
                continue;
            }

            if (! $stmt->expr instanceof Assign) {
                continue;
            }

            if (! $nextStmt->expr instanceof Assign) {
                continue;
            }

            $nextAssign = $nextStmt->expr;
            if (! $this->nodeComparator->areNodesEqual($nextAssign->var, $stmt->expr->var)) {
                continue;
            }

            // early check self referencing, ensure that variable not re-used
            if ($this->isSelfReferencing($nextAssign)) {
                continue;
            }

            // detect call expression has side effect
            // no calls on right, could hide e.g. array_pop()|array_shift()
            if ($this->sideEffectNodeDetector->detectCallExpr($stmt->expr->expr)) {
                continue;
            }

            // next stmts can have side effect as well
            if (($nextAssign->var instanceof PropertyFetch || $nextAssign->var instanceof StaticPropertyFetch) && $this->sideEffectNodeDetector->detectCallExpr(
                $nextAssign->expr
            )) {
                continue;
            }

            if (! $stmt->expr->var instanceof Variable && ! $stmt->expr->var instanceof PropertyFetch && ! $stmt->expr->var instanceof StaticPropertyFetch) {
                continue;
            }

            // side effect may throw exception, and may be handled by catch block
            if ($node instanceof TryCatch && $this->sideEffectNodeDetector->detectCallExpr($nextAssign->expr)) {
                continue;
            }

            // remove current Stmt if will be overridden in next stmt
            unset($node->stmts[$key]);

            $hasChanged = true;
        }

        if (! $hasChanged) {
            return null;
        }

        // update array keys to fit printer
        $node->stmts = array_values($node->stmts);

        return $node;
    }

    private function isSelfReferencing(Assign $assign): bool
    {
        return (bool) $this->betterNodeFinder->findFirst(
            $assign->expr,
            fn (Node $subNode): bool => $this->nodeComparator->areNodesEqual($assign->var, $subNode)
        );
    }
}