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composer 在 2020-11-24 发布了全新的 2.0 版本。参考官方博客
鉴于博客里描述新版在很多方面都做出了优化，特别是性能方面，提速了很多，于是笔者迫不及待地更新了。
测试的是无缓存下的耗时（"初始化update" + "install"），表现出了60%的提速
但是在写上一篇文章 php 调试指南（Xdebug版）的篇头处，执行 composer require mikecao/flight 缺发生了异常
[RuntimeException]
No composer.json present in the current directory, this may be the cause of the following exception.
[InvalidArgumentException]
Could not find package mikecao/flight.
Did you mean one of these?
mikecao/flight
geogkary/breeze
分析报错信息，提示找不到 mikecao/flight，又问我是不是想找 mikecao/flight。
这。。。有毒吧
会不会是 Composer 2.0 的 bug？不科学呀，不至于有这么大的bug还发布了出来。
会不会是我的配置有问题？查看一下 配置文件
$ cat ~/.composer/config.json
{
"config": {},
"repositories": {
"packagist": {
"type": "composer",
"url": "https://packagist.phpcomposer.com"
}
}
}
可以看到除了 镜像源 以外并无其他的配置。
问题会不会出在 镜像源 上呢，反正排除法就那么多选项
- 删除
镜像源 - 删除
composer二进制文件以及程序目录$HOME/.composer后重装
将 config.json 的 packagist 块删除后（亦可执行 composer config -g --unset repos.packagist），再次执行 require
$ composer require mikecao/flight
Using version ^1.3 for mikecao/flight
./composer.json has been updated
Running composer update mikecao/flight
Loading composer repositories with package information
Updating dependencies
Lock file operations: 1 install, 0 updates, 0 removals
- Locking mikecao/flight (v1.3.8)
Writing lock file
Installing dependencies from lock file (including require-dev)
Package operations: 1 install, 0 updates, 0 removals
- Installing mikecao/flight (v1.3.8): Extracting archive
Generating autoload files
Bingo! 异常报错消失了
可是该镜像源 Packagist / Composer 中国全量镜像 笔者已经使用了好多年了，怎么突然就挂了呢？网上也搜不到它的 停服 消息。
考虑到国内的网络环境，得重新找一个镜像源。
经过一番网罗，笔者最终敲定选用 阿里云 Composer 全量镜像，配置命令：
$ composer config -g repo.packagist composer https://mirrors.aliyun.com/composer/
其他的推荐镜像源：
次选镜像源：
列为次选是因为还未支持 Composer2，运行时会有 黄色警告
Composer 2 repository support for https://mirrors.xxx.com/composer has been disabled due to what seems like a misconfiguration. If this is a packagist.org mirror we recommend removing it as Composer 2 handles network operations much faster and should work fine without.
