import-local的作用
当全局node_modules和本地node_modules中，存在相同的库，则优先加载本地node_modules中的库
lerna入口文件：/cli.js
#!/usr/bin/env node
"use strict";
/* eslint-disable import/no-dynamic-require, global-require */
const importLocal = require("import-local");
if (importLocal(__filename)) {
require("npmlog").info("cli", "using local version of lerna");
} else {
require(".")(process.argv.slice(2));
}
import-local/index.js文件
'use strict';
const path = require('path');
const resolveCwd = require('resolve-cwd');
const pkgDir = require('pkg-dir');
module.exports = filename => {
const globalDir = pkgDir.sync(path.dirname(filename));
const relativePath = path.relative(globalDir, filename);
const pkg = require(path.join(globalDir, 'package.json'));
const localFile = resolveCwd.silent(path.join(pkg.name, relativePath));
// Use `path.relative()` to detect local package installation,
// because __filename's case is inconsistent on Windows
// Can use `===` when targeting Node.js 8
// See https://github.com/nodejs/node/issues/6624
return localFile && path.relative(localFile, filename) !== '' ? require(localFile) : null;
};
执行lerna命令的流程
在本地lerna源文件目录lerna-main下执行* lerna ls*的流程分析
# 执行lerna 命令
> lerna ls
# 实际是通过which找到lerna的文件路径
> which lerna
/usr/local/bin/lerna # lerna软链接
> ll /usr/local/bin/lerna
# 软链接对应的真实地址 ：/usr/local/lib/node_modules/lerna/cli.js
lrwxr-xr-x 1 song admin 32B 12 30 21:34 /usr/local/bin/lerna -> ../lib/node_modules/lerna/cli.js
# 所以执行 lerna ls 实际是执行下面的命令
> node /usr/local/lib/node_modules/lerna/cli.js ls
在lerna/cli.js 中最先执行import-lcoal
import-lcoal执行流程
