Laravel's composer.json doesn't reinstall all required packages - laravel

Question

I have this Laravel composer.json that's automatically created after running composer create-project --prefer-dist laravel/laravel blog.
Unfortunately when I run a composer install. It's only installing 38 instead of 26 required packages.
The error message on the website is:
Class 'BeyondCode\DumpServer\DumpServerServiceProvider' not found
Composer configuration:
{
"name": "laravel-distro",
"type": "project",
"description": "The Laravel Framework.",
"keywords": [
"framework",
"laravel"
],
"license": "MIT",
"require": {
"php": "^7.1.3",
"fideloper/proxy": "^4.0",
"laravel/framework": "5.8.*",
"laravel/tinker": "^1.0",
"laravel/installer": "^2.0.1"
},
"require-dev": {
"beyondcode/laravel-dump-server": "^1.0",
"filp/whoops": "^2.0",
"fzaninotto/faker": "^1.4",
"mockery/mockery": "^1.0",
"nunomaduro/collision": "^2.0",
"phpunit/phpunit": "^7.5"
},
"config": {
"optimize-autoloader": true,
"preferred-install": "dist",
"vendor-dir": "vendor",
"sort-packages": true
},
"extra": {
"laravel": {
"dont-discover": []
}
},
"autoload": {
"psr-4": {
"App\\": "app/"
}
},
"autoload-dev": {
"psr-4": {
"Tests\\": "tests/"
}
},
"minimum-stability": "dev",
"prefer-stable": true
}
Installed packages:
[laravel-distro &cli-image laravel-distro]php:/app$ ls vendor
autoload.php composer doctrine egulias fideloper jakub-onderka league nesbot opis phpoption psy ramsey symfony vlucas
bin dnoegel dragonmantank erusev guzzlehttp laravel monolog nikic paragonie psr ralouphie swiftmailer tijsverkoyen
[laravel-distro &cli-image laravel-distro]php:/app$ ls vendor_backup/
autoload.php composer dragonmantank fideloper hamcrest league myclabs nunomaduro phar-io phpspec psy swiftmailer tijsverkoyen
beyondcode dnoegel egulias filp jakub-onderka mockery nesbot opis phpdocumentor phpunit ramsey symfony vlucas
bin doctrine erusev fzaninotto laravel monolog nikic paragonie phpoption psr sebastian theseer webmozart
[laravel-distro &cli-image laravel-distro]php:/app$

Answer 1

I believe the problem might be that composer.lock is not synchronized with composer.json. Try to run
composer install
and make sure you don't have message like this:
The lock file is not up to date with the latest changes in composer.json
If you do, it means someone forgot to commit composer.lock - the easiest solution is to run:
composer update
that will cause that all packages will be updated (it might cause some problems if something in package was changed) but it should also install all the packages that are not in composer.lock file but are listed in composer.json