PHP 7.4升级至8.2：用Rector自动修复Undefined Array Key警告

针对PHP 7.4迁移至8.2后出现的大量"undefined array key"警告，以下是对应你提出的四个场景的Rector自定义规则实现方案：

场景1、2：补全数组初始化时缺失的键 #

这类场景的核心是在数组定义或+=合并操作中，自动添加代码中已访问但未初始化的键，默认赋值为null。

自定义Rector规则代码 #

use PhpParser\Node;
use PhpParser\Node\Expr\Array_;
use PhpParser\Node\Expr\ArrayDimFetch;
use PhpParser\Node\Expr\Assign;
use PhpParser\Node\Expr\AssignOp\Plus;
use PhpParser\Node\Stmt\ClassMethod;
use Rector\Core\Rector\AbstractRector;
use Symplify\RuleDocGenerator\ValueObject\CodeSample\CodeSample;
use Symplify\RuleDocGenerator\ValueObject\RuleDefinition;

final class CompleteUndefinedArrayKeysRector extends AbstractRector
{
    public function getRuleDefinition(): RuleDefinition
    {
        return new RuleDefinition(
            '补全数组初始化中缺失的、代码中已访问的键，默认赋值为null',
            [
                new CodeSample(
                    <<<'CODE_SAMPLE'
$options = ['key1' => 'key1Value'];
echo $options['key2'];
CODE_SAMPLE
                    ,
                    <<<'CODE_SAMPLE'
$options = ['key1' => 'key1Value', 'key2' => null];
echo $options['key2'];
CODE_SAMPLE
                ),
            ]
        );
    }

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

    /**
     * @param Assign|Plus $node
     */
    public function refactor(Node $node): ?Node
    {
        if (!$node->var instanceof Node\Expr\Variable) {
            return null;
        }
        $arrayVarName = $this->getName($node->var);
        if ($arrayVarName === null) {
            return null;
        }

        $accessedKeys = [];
        $parentMethod = $this->betterNodeFinder->findParentType($node, ClassMethod::class);
        if (!$parentMethod instanceof ClassMethod) {
            return null;
        }

        $this->traverseNodesWithCallable((array)$parentMethod->stmts, function (Node $subNode) use ($arrayVarName, &$accessedKeys) {
            if (!$subNode instanceof ArrayDimFetch) {
                return null;
            }
            if (!$subNode->var instanceof Node\Expr\Variable || $this->getName($subNode->var) !== $arrayVarName) {
                return null;
            }
            if (!$subNode->dim instanceof Node\Scalar\String_) {
                return null;
            }
            $key = $subNode->dim->value;
            $accessedKeys[$key] = true;
        });

        $currentArray = $node instanceof Assign ? $node->expr : $node->expr;
        if (!$currentArray instanceof Array_) {
            return null;
        }
        $currentKeys = [];
        foreach ($currentArray->items as $item) {
            if (!$item->key instanceof Node\Scalar\String_) {
                continue;
            }
            $currentKeys[$item->key->value] = true;
        }

        foreach ($accessedKeys as $key => $_) {
            if (!isset($currentKeys[$key])) {
                $newItem = new Node\Expr\ArrayItem(
                    new Node\Expr\ConstFetch(new Node\Name('null')),
                    new Node\Scalar\String_($key)
                );
                $currentArray->items[] = $newItem;
            }
        }

        return $node;
    }
}

场景3、4：给条件判断中的数组访问添加空合并运算符 #

这类场景需要识别条件表达式中的数组键访问，自动包裹?? null避免警告。

自定义Rector规则代码 #

use PhpParser\Node;
use PhpParser\Node\Expr\ArrayDimFetch;
use PhpParser\Node\Expr\BinaryOp\Coalesce;
use PhpParser\Node\Expr\ConstFetch;
use PhpParser\Node\Name;
use PhpParser\Node\Stmt\If_;
use Rector\Core\Rector\AbstractRector;
use Symplify\RuleDocGenerator\ValueObject\CodeSample\CodeSample;
use Symplify\RuleDocGenerator\ValueObject\RuleDefinition;

final class WrapArrayDimFetchInCoalesceRector extends AbstractRector
{
    public function getRuleDefinition(): RuleDefinition
    {
        return new RuleDefinition(
            '给条件判断中的数组键访问添加?? null，避免undefined array key警告',
            [
                new CodeSample(
                    <<<'CODE_SAMPLE'
if ($options['key2']) {
    echo $options['key2'];
}
CODE_SAMPLE
                    ,
                    <<<'CODE_SAMPLE'
if ($options['key2'] ?? null) {
    echo $options['key2'];
}
CODE_SAMPLE
                ),
            ]
        );
    }

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

    /**
     * @param If_ $node
     */
    public function refactor(Node $node): ?Node
    {
        $this->traverseNodesWithCallable([$node->cond], function (Node $subNode) {
            if (!$subNode instanceof ArrayDimFetch) {
                return null;
            }
            if ($subNode->getAttribute('already_wrapped')) {
                return null;
            }
            $coalesce = new Coalesce(
                $subNode,
                new ConstFetch(new Name('null'))
            );
            $subNode->setAttribute('already_wrapped', true);
            return $coalesce;
        });

        return $node;
    }
}

使用说明 #

1. 将上述两个规则放入你的Rector项目的src/Rector目录下，替换命名空间为你的项目命名空间
2. 在rector.php中注册规则：

use Rector\Config\RectorConfig;

return static function (RectorConfig $rectorConfig): void {
    $rectorConfig->rule(\YourProjectNamespace\CompleteUndefinedArrayKeysRector::class);
    $rectorConfig->rule(\YourProjectNamespace\WrapArrayDimFetchInCoalesceRector::class);
};

3. 运行Rector命令执行修复：vendor/bin/rector process src

注意：当前规则仅处理字符串类型的数组键，若需支持数字键等其他类型，可修改对应节点判断逻辑。

内容的提问来源于stack exchange，提问作者Chirag Kalani