How to Complete Type Declarations without Docblocks with Rector

2019-01-03

Well, you're doomed, because you should write docblocks everywhere where useful.

<?php

class SomeClass
{
    public function getItems()
    {
        return ['Statie', 'EasyCodingStandard', 'Rector'];
    }
}

If you only typed @return annotation 4 years ago, where no-one thought there will ever be scalar type declarations and such annotations were only for geeks. Transition to PHP 7 features would be so easy:

 <?php

 class SomeClass
 {
-    public function getItems()
+    public function getItems(): array
     {
         return ['Statie', 'EasyCodingStandard', 'Rector'];
     }
 }

Now, I hope you've learned, that future compatibility is a thing and you'll write annotations to each property, so they Rector will convert them to type declarations once PHP 7.4 is out.

"It's Not My Fault"

Well, but what if you've inherited such legacy code, are you to blame? No, no-one is to blame even if you wrote the code. That's how change works. We feel like we know all today, but in 5 years array-type declarations will be considered code smell and we keep it only for historical reasons.

So how can we fight the change together?

<?php

class SomeClass
{
    public function getItems()
    {
        $items = ['Statie', 'EasyCodingStandard', 'Rector'];

         return $this->sortItems($items);
    }

    private function sortItems(array $items)
    {
        sort($items);
        return $items;
    }
}

How would upgrade this code to type declarations?

 <?php

 class SomeClass
 {
-    public function getItems()
+    public function getItems(): array
     {
         $items = ['Statie', 'EasyCodingStandard', 'Rector'];

         return $this->sortItems($items);
     }

-    private function sortItems(array $items)
+    private function sortItems(array $items): array
     {
         sort($items);
         return $items;
     }
 }

Good job, that's correct! Now you can do it for the rest of your 25 000 lines of code.

Or... You can be lazy smart and use static analysis from PHPStan to do it for you. It already knows that:

• $items is array with strings
• sort sorts array and keeps it an array

That was too easy... let's check case we'll find in our code:

 <?php

 // ...

-public function getResult()
+public function getResult(): float
 {
     if (true) {
         return 5.2;
     }

     $value = 5.3;

     return $value;
 }

Don't get confused by incorrect doc:

 /**
  * @return bool
  */
-public function getNumber()
+public function getNumber(): int
 {
     return 5;
 }

Is one object or null?

 <?php

 // ...

-public function resolve(Product $product)
+public function resolve(Product $product): ?Product
 {
     // ...

     if (...) {
         return null;
     }

     return $product;
 }

If PHPStorm or PHPStan knows what type it is,
there is a big chance Rector can change it everywhere in your code.

Honza Kuchař spend one afternoon over Rector with me and motivated me to add this feature to Rector, so PHP developers can enjoy the laziness AST provides. Thank you, Honza! It's done (see PR).

Just setup Rector and upgrade your code:

<?php

// rector.php

declare(strict_types=1);

use Rector\TypeDeclaration\Rector\FunctionLike\ReturnTypeDeclarationRector;
use Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator;

return function (ContainerConfigurator $containerConfigurator): void {
    $services = $containerConfigurator->services();
    $services->set(ReturnTypeDeclarationRector::class);
};

vendor/bin/rector process src

Done!

Just one more thing...

Properties Without @var?

There is a big chance that if our code misses @param and @return type declarations, the @var is missing as well. We don't have to go to legacy code to find such code.

Do you recognize this class?

<?php

namespace Symfony\Component\Console\Command;

use Symfony\Component\Console\Application;

class Command
{
    private $application;
    private $name;
    private $processTitle;
    private $aliases = [];
    private $definition;
    private $hidden = false;
    private $help;
    private $description;
    private $ignoreValidationErrors = false;
    private $applicationDefinitionMerged = false;
    private $applicationDefinitionMergedWithArgs = false;
    private $code;
    private $synopsis = [];
    private $usages = [];
    private $helperSet;

    // ...

    public function setApplication(Application $application = null)
    {
        $this->application = $application;
    }
}

Quiz question: how would you utilize AST to autocomplete all @var annotations to properties above?

$this->application = $application; we know that $application can be upgraded to:

+/**
+ * @var \Symfony\Component\Console\Application
+ */
 private $application;

That's it! Let's put this algorithm into Rector:

<?php

// rector.php

declare(strict_types=1);

use Rector\TypeDeclaration\Rector\Property\CompleteVarDocTypePropertyRector;
use Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator;

return function (ContainerConfigurator $containerConfigurator): void {
    $services = $containerConfigurator->services();
    $services->set(CompleteVarDocTypePropertyRector::class);
};

vendor/bin/rector process src

↓

 <?php

 namespace Symfony\Component\Console\Command;

 use Symfony\Component\Console\Application;

 class Command
 {
+    /**
+     * @var \Symfony\Component\Console\Application
+     */
     private $application;
+    /**
+     * @var string
+     */
     private $name;
+    /**
+     * @var string
+     */
     private $processTitle;
+    /**
+     * @var mixed[]|string[]
+     */
     private $aliases = [];
+    /**
+     * @var \Symfony\Component\Console\Input\InputDefinition
+     */
     private $definition;
+    /**
+     * @var bool
+     */
     private $hidden = false;
+    /**
+     * @var string
+     */
     private $help;
+    /**
+     * @var string
+     */
     private $description;
+    /**
+     * @var bool
+     */
     private $ignoreValidationErrors = false;
+    /**
+     * @var bool
+     */
     private $applicationDefinitionMerged = false;
+    /**
+     * @var bool
+     */
     private $applicationDefinitionMergedWithArgs = false;
+    /**
+     * @var callable
+     */
     private $code;
+    /**
+     * @var mixed[]
+     */
     private $synopsis = [];
+    /**
+     * @var mixed[]
+     */
     private $usages = [];
+    /**
+     * @var \Symfony\Component\Console\Helper\HelperSet
+     */
     private $helperSet;

In matter of seconds now we have:

• Better static type analysis ✅
• Better PHPStorm autocomplete ✅
• Better coding standards ✅
• No manual boring work required from the developer ✅

If you want to how Rector works behind this scene, (check the PR). The code size to make this happen is not what you'd expect thanks to php-parser elegance (thanks Nikic!).

What more could be done to turn legacy code to elegant code? Share in comments, I'm eager to know.

Happy coding!