composer update返回installed.json" does not contain valid JSON

Question

我修改了composer.json,从

{
    "name": "laravel/laravel",
    "description": "The Laravel Framework.",
    "keywords": ["framework", "laravel"],
    "license": "MIT",
    "type": "project",
    "require": {
        "php": ">=5.6.4",
        "laravel/framework": "5.4.*",
        "laravel/tinker": "~1.0",
        "predis/predis": "^1.1"
    },
    "require-dev": {
        "fzaninotto/faker": "~1.4",
        "mockery/mockery": "0.9.*",
        "phpunit/phpunit": "~5.7"
    },
    "autoload": {
        "classmap": [
            "database"
        ],
        "psr-4": {
            "App\\": "app/"
        }
    },
    "autoload-dev": {
        "psr-4": {
            "Tests\\": "tests/"
        }
    },
    "scripts": {
        "post-root-package-install": [
            "php -r \"file_exists('.env') || copy('.env.example', '.env');\""
        ],
        "post-create-project-cmd": [
            "php artisan key:generate"
        ],
        "post-install-cmd": [
            "Illuminate\\Foundation\\ComposerScripts::postInstall",
            "php artisan optimize"
        ],
        "post-update-cmd": [
            "Illuminate\\Foundation\\ComposerScripts::postUpdate",
            "php artisan optimize"
        ]
    },
    "config": {
        "preferred-install": "dist",
        "sort-packages": true,
        "optimize-autoloader": true
    }
}

修改为了

{
    "name": "laravel/laravel",
    "description": "The Laravel Framework.",
    "keywords": ["framework", "laravel"],
    "license": "MIT",
    "type": "project",
    "require": {
        "php": ">=5.6.4",
        "laravel/framework": "5.5.*",
        "laravel/tinker": "~1.0",
        "predis/predis": "^1.1"
    },
    "require-dev": {
        "fzaninotto/faker": "~1.4",
        "mockery/mockery": "0.9.*",
        "phpunit/phpunit": "~6.0",
        "filp/whoops": "~2.0",

    },
    "autoload": {
        "classmap": [
            "database"
        ],
        "psr-4": {
            "App\\": "app/"
        }
    },
    "autoload-dev": {
        "psr-4": {
            "Tests\\": "tests/"
        }
    },
    "scripts": {
        "post-root-package-install": [
            "php -r \"file_exists('.env') || copy('.env.example', '.env');\""
        ],
        "post-create-project-cmd": [
            "php artisan key:generate"
        ],
        "post-install-cmd": [
            "Illuminate\\Foundation\\ComposerScripts::postInstall",
            "php artisan optimize"
        ],
        "post-update-cmd": [
            "Illuminate\\Foundation\\ComposerScripts::postUpdate",
            "php artisan optimize"
        ],
        "post-autoload-dump": [
        "Illuminate\\Foundation\\ComposerScripts::postAutoloadDump",
        "@php artisan package:discover"
    ],
    },
    "config": {
        "preferred-install": "dist",
        "sort-packages": true,
        "optimize-autoloader": true
    }
}

即根据官方文档把laravel5.4升级为了laravel5.5，然后执行composer update，他返回了这个错误

然后我去查看"/home/vagrant/work/exports-api/vendor/composer/installed.json"文件
是一片空白，什么都没有，请问有大神知道这是什么问题吗
我上网查，好像说是镜像源的问题，但是我的源已经是阿里的源了，所以很奇怪

补充说明
没更新之前installed.json是有东西的，composer update就变一片空白了，然后现在是在这个项目下执行composer的操作都会返回这个错误

Answer 1

直接把vendor目录 删除就是了. 这目录没用. 也不进代码库.
然后再更新.