Framework: [5.4] ConvertEmptyStringsToNull middleware is causing problems in validation

[ankurk91]

• Laravel Version: 5.4.6
• PHP Version: 7.0.8
• Database Driver & Version: MySql 5.6.30

Description:

I upgrade my project from 5.3 to 5.4, everything worked fine.
Now i am facing issues when an input field is optional and submitted as empty string.

Steps To Reproduce:

Lets have a validation request class with rules like -

'amount' => 'numeric|min:0|max:9999',

```html

This field is optional, when we submit the form without typing anything into text field it should pass the validation. But it not. 
If we comment out ```ConvertEmptyStringsToNull``` middleware it passes the validation.
This is not related to ```numeric``` validation. It applies to all type of validations for eg ```alpha```

FYI: I have those two new middlewares in ```Kernal.php``` .
```php
protected $middleware = [
        \Illuminate\Foundation\Http\Middleware\CheckForMaintenanceMode::class,
        \Illuminate\Foundation\Http\Middleware\ValidatePostSize::class,
        \App\Http\Middleware\TrimStrings::class,
        \Illuminate\Foundation\Http\Middleware\ConvertEmptyStringsToNull::class,
    ];

[laurencei]

What is the validation error you are getting?

[ankurk91]

@lioannou
I am getting the desired validation error message for this field. Here is the message.

The amount must be a number.

[joseaneto]

Same problem here using "required_with":

        'password' => 'max:200',
        'repeat_password' => 'required_with:password|max:200|same:password',

With password field empty I have a error in repeat_password:

The repeat password and password must match.

Removing the middleware ConvertEmptyStringsToNull works as expected.

[fernandobandeira]

What happens when you use "nullable"?

[ankurk91]

@fernandobandeira

Adding nullable to rule passes the validation. This can be a workaround.

'amount' => 'nullable|numeric|min:0|max:9999',

PS - Such changes should be documented somewhere.
PS2 - Taylor added a note about optional fields on docs see

[fernandobandeira]

This is a duplicate of #17558 btw...
This is the intended behavior...

ping @themsaid It seems there's an increasing number of issues like this one, should we add a warning on the validation docs? This middleware is enabled by default...

[themsaid]

Here's a blog post describing the issue http://themsaid.com/laravel-convert-empty-strings-to-null-20170130/

I'm not sure if it should be in the docs though, maybe the upgrade guide :)

Please feel free to PR the docs to add a hint about that if you want.

[IJack]

@themsaid I add to my validation nullable, but nw I get many issues with saving the data. Does ConvertEmptyStringsToNull convert my value to "null" also for storing the data, or just for the validation session?

[themsaid]

It converts empty request parameters to null, so yeah it'll hit the database as null.

The middleware is not mandatory, you can comment it and get back to the 5.3 behaviour easily.