File Explorer

1// if the thing isn't there, skip it2// if there's a non-symlink there already, eexist3// if there's a symlink already, pointing somewhere else, eexist4// if there's a symlink already, pointing into our pkg, remove it first5// then create the symlink6 7const { resolve, dirname, sep } = require('path')8const { lstat, mkdir, readlink, rm, symlink } = require('fs/promises')9const { log } = require('proc-log')10const throwSignificant = er => {11  if (er.code === 'ENOENT') {12    return13  }14  if (er.code === 'EACCES') {15    log.warn('error adding file', er.message)16    return17  }18  throw er19}20 21const rmOpts = {22  recursive: true,23  force: true,24}25 26// even in --force mode, we never create a link over a link we've27// already created.  you can have multiple packages in a tree trying28// to contend for the same bin, or the same manpage listed multiple times,29// which creates a race condition and nondeterminism.30const seen = new Set()31 32const SKIP = Symbol('skip - missing or already installed')33const CLOBBER = Symbol('clobber - ours or in forceful mode')34 35const linkGently = async ({ path, to, from, absFrom, force }) => {36  if (seen.has(to)) {37    return false38  }39  seen.add(to)40 41  // if the script or manpage isn't there, just ignore it.42  // this arguably *should* be an install error of some sort,43  // or at least a warning, but npm has always behaved this44  // way in the past, so it'd be a breaking change45  return Promise.all([46    lstat(absFrom).catch(throwSignificant),47    lstat(to).catch(throwSignificant),48  ]).then(([stFrom, stTo]) => {49    // not present in package, skip it50    if (!stFrom) {51      return SKIP52    }53 54    // exists! maybe clobber if we can55    if (stTo) {56      if (!stTo.isSymbolicLink()) {57        return force && rm(to, rmOpts).then(() => CLOBBER)58      }59 60      return readlink(to).then(target => {61        if (target === from) {62          return SKIP63        } // skip it, already set up like we want it.64 65        target = resolve(dirname(to), target)66        if (target === path || target.startsWith(path + sep) || force) {67          return rm(to, rmOpts).then(() => CLOBBER)68        }69        // neither skip nor clobber70        return false71      })72    } else {73      // doesn't exist, dir might not either74      return mkdir(dirname(to), { recursive: true })75    }76  })77    .then(skipOrClobber => {78      if (skipOrClobber === SKIP) {79        return false80      }81      return symlink(from, to, 'file').catch(er => {82        if (skipOrClobber === CLOBBER || force) {83          return rm(to, rmOpts).then(() => symlink(from, to, 'file'))84        }85        throw er86      }).then(() => true)87    })88}89 90const resetSeen = () => {91  for (const p of seen) {92    seen.delete(p)93  }94}95 96module.exports = Object.assign(linkGently, { resetSeen })97