Add Rule: nullable_type_declaration

[Jubeki]

PHP-CS-Fixer Rule: nullable_type_declaration

With the given configuration this will change it like this (Taken from the PHP-CS-Fixer Page):

--- Original
+++ New
 <?php
-function bar(null|int $value, null|\Closure $callable): void {}
+function bar(?int $value, ?\Closure $callable): void {}

--- Original
+++ New
 <?php
 class ValueObject
 {
-    public null|string $name;
+    public ?string $name;
     public ?int $count;
-    public null|bool $internal;
-    public null|\Closure $callback;
+    public ?bool $internal;
+    public ?\Closure $callback;
 }

[driesvints]

Thanks @Jubeki but I don't think we should do this. It's true that right now we do this in our own codebase but null is a valid type in PHP 8.2

If people have PHP 8.2 as a default for their project they'll probably want to use null instead of ?. So this could be opinionated. In the future when 8.2 is the minimum for Laravel and all of its first party packages (which is still a while away. And Pint has 8.2 as a default, we could change it to enforce null instead.

Side note: I also think null should always be placed as the last type like |null.

[Jubeki]

@driesvints I understand that, I don't think there as currently a rule where |null will be enforced at the end.

If you take a look at this PR/rule: #192 there would als be a configuration where the |null is added at the end (instead of only removing the null or question_mark).

Edit: I took a look at the rule, which I referenced, it also doesn't always enforce the |null with default values.

[browner12]

I'm with @driesvints on this one. Much prefer |null over ?

[zepfietje]

I'm with @driesvints on this one. Much prefer |null over ?

Me too. Also, it's already valid starting with PHP 8.0. PHP 8.2 added support for null as a standalone type, but that's not what this PR and rule are about.

[Wirone]

FYI: Instead of 'nullable_type_declaration' => true, you just could do 'nullable_type_declaration' => ['syntax' => 'union'], because rule works both ways.