How to Create Typo Variable Fixer with Rector

Rector is a code refactoring tool that can help us with major code changes (like upgrade legacy code) or daily work. There are already many rules that ready to use for us.

What if we want a custom rule, like we want a daily work can to do “Typo” check in variables? In this post, I want to show you how to create a Typo Variable Fixer with Rector, a custom Rector rule!

Preparation

First, let say, we build a new app, we use composer for it with add rector/rector to require-dev:

composer init


  Welcome to the Composer config generator



This command will guide you through creating your composer.json config.

Package name (<vendor>/<name>) [samsonasik/how-to-create-typo-variable-fixer]: samsonasik/app

Description []: App Demo

Author [Abdul Malik Ikhsan <samsonasik@gmail.com>, n to skip]:

Minimum Stability []:

Package Type (e.g. library, project, metapackage, composer-plugin) []:

License []: MIT

Define your dependencies.

Would you like to define your dependencies (require) interactively [yes]? no
Would you like to define your dev dependencies (require-dev) interactively [yes]? yes
Search for a package: rector/rector
Enter the version constraint to require (or leave blank to use the latest version):

Using version ^0.8.40 for rector/rector

Search for a package:

{
    "name": "samsonasik/app",
    "description": "App Demo",
    "require-dev": {
        "rector/rector": "^0.8.40"
    },
    "license": "MIT",
    "authors": [
        {
            "name": "Abdul Malik Ikhsan",
            "email": "samsonasik@gmail.com"
        }
    ],
    "require": {}
}

Do you confirm generation [yes]? yes
Would you like to install dependencies now [yes]? yes

After it, let say we need an app directory, we can create an app directory and write a php file inside it:

mkdir -p app && touch app/app.php

with file app/app.php content:

<?php

namespace App;

$previuos = 0;
$begining = 1;
$statment = $previuos . ' is lower than ' . $begining;

Yes, there are 3 typos in above file! For example, we will have a sample library.php file for common typos, for example, inside utils directory:

mkdir -p utils && touch utils/library.php

with file utils/library.php content:

<?php

namespace Utils;

return [
    'previous' => ['previuos', 'previuous'],
    'beginning' => ['begining', 'beginign'],
    'statement' => ['statment'],
];

We can setup composer autoload for with add the following to our composer.json file:

    "autoload": {
        "psr-4": {
            "App\\": "app"
        }
    },
    "autoload-dev": {
        "psr-4": {
            "Utils\\": "utils"
        }
    }

After it, run composer dump-autoload command:

composer dump-autoload

The preparation is done!

Create the Typo Fixer Rule

We can follow the Rector‘s documentation to create new custom rule. So, for example, we create TypoVariableFixerRule under own utils/Rector directory:

mkdir -p utils/Rector && touch utils/Rector/TypoVariableFixerRule.php

Our directory will looks like the following:

.
├── app
│   └── app.php
├── composer.json
├── utils
│   ├── Rector
│   │   └── TypoVariableFixerRule.php
│   └── library.php

Now, we can start create the TypoVariableFixerRule:

<?php

declare(strict_types=1);

namespace Utils\Rector;

use PhpParser\Node;
use PhpParser\Node\Expr\Variable;
use Rector\Core\Rector\AbstractRector;
use Rector\Core\RectorDefinition\CodeSample;
use Rector\Core\RectorDefinition\RectorDefinition;

final class TypoVariableFixerRule extends AbstractRector
{
    public function getNodeTypes(): array
    {
        return [Variable::class];
    }

    /**
     * @param Variable $node
     */
    public function refactor(Node $node): ?Node
    {
        return $node;
    }

    public function getDefinition(): RectorDefinition
    {
        return new RectorDefinition(
            'Change Typo in variable', [
                new CodeSample(
                    // code before
                    '$previuos',
                    // code after
                    '$previous'
                ),
            ]
        );
    }
}

Above, we extends AbstractRector for new Rector rule. We operate with nikic/php-parser to do refactor. The getNodeTypes returns the node that we want to refactor, at this case, we want to refactor Variable node in our refactor method.

Before we continue, let’s register our new TypoVariableFixerRule to rector config to ensure it works. We can create rector config as follow:

touch rector.php

with file rector.php content:

<?php

use Rector\Core\Configuration\Option;
use Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator;
use Utils\Rector\TypoVariableFixerRule;

return static function (ContainerConfigurator $containerConfigurator): void {
    $parameters = $containerConfigurator->parameters();
    $parameters->set(Option::PATHS, [__DIR__ . '/app']);

    $services = $containerConfigurator->services();
    $services->set(TypoVariableFixerRule::class);
};

and test with run:

vendor/bin/rector process

So we see the “Green” OK:

Now, time to make refactor work! We can modify the refactor method:

    public function refactor(Node $node): ?Node
    {
        // get the variable name
        $variableName = $this->getName($node);

        // get the library content
        $library = include 'utils/library.php';

        foreach ($library as $correctWord => $commonTypos) {
            if (! in_array($variableName, $commonTypos, true)) {
                continue;
            }

            $node->name = $correctWord;
            return $node;
        }

        return null;
    }

Above, we find if the variable name is in common typos, then we return node (as variable) with updated its name with the correct word. Now, let’s run it with --dry-run to see the diff that can be made:

vendor/bin/rector process --dry-run

and we can see:

Seems great! Let’s apply the changes:

vendor/bin/rector process

Awesome! We now already make typo fixer succesfully working! Let’s run again, and it will take no effect as already fixed:

That’s it!