Modifying Spark's login to use username instead of email

@clat23 I am supposing that you are having a username field under the Users table

your User.php

protected $fillable = ['name', 'email', 'password', 'username'];

Secondly change the input type field from 'email' to 'text' from the login.blade.php

<input id="email" type="text" class="form-control{{ $errors->has('email') ? ' is-invalid' : '' }}" name="email" value="{{ old('email') }}" required autofocus>

your LoginController

protected function credentials(Request $request)
    {
        $field = $this->field($request);

        return [
            $field => $request->get($this->username()),
            'password' => $request->get('password'),
        ];
    }

public function field(Request $request)
    {
        $email = $this->username();

        return filter_var($request->get($email), FILTER_VALIDATE_EMAIL) ? $email : 'username';
    }


protected function validateLogin(Request $request)
    {
        $field = $this->field($request);

        $messages = ["{$this->username()}.exists" => 'The account you are trying to login is not registered or it has been disabled.'];

        $this->validate($request, [
            $this->username() => "required|exists:users,{$field}",
            'password' => 'required',
        ], $messages);
    }

@rameezisrar Thanks, but it didn't work...

Spark 8.0 (Laravel 5.8)

app/database/migrations/2019_07_30_171753_create_users_table.php:

<?php

use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class CreateUsersTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::create('users', function (Blueprint $table) {
            $table->increments('id');
            $table->string('name');
            $table->string('email');
            $table->string('username')->unique();
            $table->string('timezone');
            $table->timestamp('email_verified_at')->nullable();
            $table->string('password');
            $table->rememberToken();
            $table->text('photo_url')->nullable();
            $table->tinyInteger('uses_two_factor_auth')->default(0);
            $table->string('authy_id')->nullable();
            $table->string('country_code', 10)->nullable();
            $table->string('phone', 25)->nullable();
            $table->string('two_factor_reset_code', 100)->nullable();
            $table->integer('current_team_id')->nullable();
            $table->string('stripe_id')->nullable();
            $table->string('current_billing_plan')->nullable();
            $table->string('card_brand')->nullable();
            $table->string('card_last_four')->nullable();
            $table->string('card_country')->nullable();
            $table->string('billing_address')->nullable();
            $table->string('billing_address_line_2')->nullable();
            $table->string('billing_city')->nullable();
            $table->string('billing_state')->nullable();
            $table->string('billing_zip', 25)->nullable();
            $table->string('billing_country', 2)->nullable();
            $table->string('vat_id', 50)->nullable();
            $table->text('extra_billing_information')->nullable();
            $table->timestamp('trial_ends_at')->nullable();
            $table->timestamp('last_read_announcements_at')->nullable();
            $table->timestamps();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::drop('users');
    }
}

app\User.php:

<?php

namespace App;

use Laravel\Spark\CanJoinTeams;
use Laravel\Spark\User as SparkUser;

class User extends SparkUser
{
    use CanJoinTeams;

    /**
     * The attributes that are mass assignable.
     *
     * @var array
     */
    protected $fillable = [
        'name',
        'email',
        'password',
        'username'
    ];

    /**
     * The attributes excluded from the model's JSON form.
     *
     * @var array
     */
    protected $hidden = [
        'password',
        'remember_token',
        'authy_id',
        'country_code',
        'phone',
        'card_brand',
        'card_last_four',
        'card_country',
        'billing_address',
        'billing_address_line_2',
        'billing_city',
        'billing_zip',
        'billing_country',
        'extra_billing_information',
    ];

    /**
     * The attributes that should be cast to native types.
     *
     * @var array
     */
    protected $casts = [
        'trial_ends_at' => 'datetime',
        'uses_two_factor_auth' => 'boolean',
    ];
}

app/resources/views/vendor/spark/auth/login.blade.php

@extends('spark::layouts.app')

@section('content')
<div class="container">
    <div class="row justify-content-center">
        <div class="col-lg-8">
            <div class="card card-default">
                <div class="card-header">{{__('Login')}}</div>

                <div class="card-body">
                    @include('spark::shared.errors')

                    <form role="form" method="POST" action="/login">
                        {{ csrf_field() }}

                        <!-- Username -->
                        <div class="form-group row">
                            <label class="col-md-4 col-form-label text-md-right">Username</label>

                            <div class="col-md-6">
                                <input type="text" class="form-control" name="username" value="{{ old('username') }}" autofocus>
                            </div>
                        </div>

                        <!-- Password -->
                        <div class="form-group row">
                            <label class="col-md-4 col-form-label text-md-right">{{__('Password')}}</label>

                            <div class="col-md-6">
                                <input type="password" class="form-control" name="password">
                            </div>
                        </div>

                        <!-- Remember Me -->
                        <div class="form-group row">
                            <div class="col-md-6 offset-md-4">
                                <div class="form-check">
                                    <label class="form-check-label">
                                        <input type="checkbox" name="remember" class="form-check-input"> {{__('Remember Me')}}
                                    </label>
                                </div>
                            </div>
                        </div>

                        <!-- Login Button -->
                        <div class="form-group row mb-0">
                            <div class="col-md-6 offset-md-4">
                                <button type="submit" class="btn btn-primary">
                                    {{__('Login')}}
                                </button>

                                <a class="btn btn-link" href="{{ url('/password/reset') }}">{{__('Forgot Your Password?')}}</a>
                            </div>
                        </div>
                    </form>
                </div>
            </div>
        </div>
    </div>
</div>
@endsection

app\Http\Controllers\Auth\LoginController.php

<?php

namespace App\Http\Controllers\Auth;

use App\Http\Controllers\Controller;
use Illuminate\Foundation\Auth\AuthenticatesUsers;

class LoginController extends Controller
{
    /*
    |--------------------------------------------------------------------------
    | Login Controller
    |--------------------------------------------------------------------------
    |
    | This controller handles authenticating users for the application and
    | redirecting them to your home screen. The controller uses a trait
    | to conveniently provide its functionality to your applications.
    |
    */

    use AuthenticatesUsers;

    /**
     * Where to redirect users after login.
     *
     * @var string
     */
    protected $redirectTo = '/home';

    /**
     * Create a new controller instance.
     *
     * @return void
     */
    public function __construct()
    {
        $this->middleware('guest')->except('logout');
    }

    protected function credentials(Request $request)
    {
        $field = $this->field($request);

        return [
            $field => $request->get($this->username()),
            'password' => $request->get('password'),
        ];
    }

    public function field(Request $request)
    {
        $email = $this->username();

        return filter_var($request->get($email), FILTER_VALIDATE_EMAIL) ? $email : 'username';
    }


    protected function validateLogin(Request $request)
    {
        $field = $this->field($request);

        $messages = ["{$this->username()}.exists" => 'The account you are trying to login is not registered or it has been disabled.'];

        $this->validate($request, [
            $this->username() => "required|exists:users,{$field}",
            'password' => 'required',
        ], $messages);
    }
}

However, when I add the following to app\Http\Controllers\Auth\LoginController.php:

public function username()
{
  return 'username';
}

I am still receiving the message: "Whoops! Something went wrong! The email field is required".

Spark has its own LoginController at app\spark\src\Http\Controllers\Auth\LoginController.php so adding

public function username()
{
  return 'username';
}

to app\Http\Controllers\Auth\LoginController.php will not do anything as Spark uses its own LoginController as mentioned above. To ensure proper implementation of

public function username()
{
  return 'username';
}

as per Laravel (not Spark) documentation on "Username Customization" (https://laravel.com/docs/5.8/authentication#included-authenticating) you must add the following to app\routes\web.php:

Route::post('/login', 'Auth\LoginController@login');