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'use strict'
const path = require('path')
const fs = require('graceful-fs')
const chain = require('slide').chain
const mkdir = require('mkdirp')
const rm = require('./rm.js')
exports = module.exports = {
link: link,
linkIfExists: linkIfExists
}
function linkIfExists (from, to, opts, cb) {
fs.stat(from, function (er) {
if (er) return cb()
fs.readlink(to, function (er, fromOnDisk) {
// if the link already exists and matches what we would do,
// we don't need to do anything
if (!er) {
var toDir = path.dirname(to)
var absoluteFrom = path.resolve(toDir, from)
var absoluteFromOnDisk = path.resolve(toDir, fromOnDisk)
if (absoluteFrom === absoluteFromOnDisk) return cb()
}
link(from, to, opts, cb)
})
})
}
function resolveIfSymlink (maybeSymlinkPath, cb) {
fs.lstat(maybeSymlinkPath, function (err, stat) {
if (err) return cb.apply(this, arguments)
if (!stat.isSymbolicLink()) return cb(null, maybeSymlinkPath)
fs.readlink(maybeSymlinkPath, cb)
})
}
function ensureFromIsNotSource (from, to, cb) {
resolveIfSymlink(from, function (err, fromDestination) {
if (err) return cb.apply(this, arguments)
if (path.resolve(path.dirname(from), fromDestination) === path.resolve(to)) {
return cb(new Error('Link target resolves to the same directory as link source: ' + to))
}
cb.apply(this, arguments)
})
}
function link (from, to, opts, cb) {
to = path.resolve(to)
opts.base = path.dirname(to)
var absTarget = path.resolve(opts.base, from)
var relativeTarget = path.relative(opts.base, absTarget)
var target = opts.absolute ? absTarget : relativeTarget
chain(
[
[ensureFromIsNotSource, absTarget, to],
[fs, 'stat', absTarget],
[rm, to, opts],
[mkdir, path.dirname(to)],
[fs, 'symlink', target, to, 'junction']
],
cb
)
}
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