code to make tests pass

index.js

@@ -0,0 +1,71 @@
+const cache = new Map()
+const fs = require('fs')
+const { dirname, resolve } = require('path')
+
+
+const lstat = path => new Promise((res, rej) =>
+  fs.lstat(path, (er, st) => er ? rej(er) : res(st)))
+
+const inferOwner = path => {
+  path = resolve(path)
+  if (cache.has(path))
+    return Promise.resolve(cache.get(path))
+
+  const statThen = st => {
+    const { uid, gid } = st
+    cache.set(path, { uid, gid })
+    return { uid, gid }
+  }
+  const parent = dirname(path)
+  const parentTrap = parent === path ? null : er => {
+    return inferOwner(parent).then((owner) => {
+      cache.set(path, owner)
+      return owner
+    })
+  }
+  return lstat(path).then(statThen, parentTrap)
+}
+
+const inferOwnerSync = path => {
+  path = resolve(path)
+  if (cache.has(path))
+    return cache.get(path)
+
+  const parent = dirname(path)
+
+  // avoid obscuring call site by re-throwing
+  // "catch" the error by returning from a finally,
+  // only if we're not at the root, and the parent call works.
+  let threw = true
+  try {
+    const st = fs.lstatSync(path)
+    threw = false
+    const { uid, gid } = st
+    cache.set(path, { uid, gid })
+    return { uid, gid }
+  } finally {
+    if (threw && parent !== path) {
+      const owner = inferOwnerSync(parent)
+      cache.set(path, owner)
+      return owner // eslint-disable-line no-unsafe-finally
+    }
+  }
+}
+
+const inflight = new Map()
+module.exports = path => {
+  path = resolve(path)
+  if (inflight.has(path))
+    return Promise.resolve(inflight.get(path))
+  const p = inferOwner(path).then(owner => {
+    inflight.delete(path)
+    return owner
+  })
+  inflight.set(path, p)
+  return p
+}
+module.exports.sync = inferOwnerSync
+module.exports.clearCache = () => {
+  cache.clear()
+  inflight.clear()
+}