The code and tests

osenv.js

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+var isWindows = process.platform === 'win32'
+console.error('isWindows = %j', isWindows, process.platform)
+var windir = isWindows ? process.env.windir || 'C:\\Windows' : null
+var path = require('path')
+var exec = require('child_process').exec
+
+// looking up envs is a bit costly.
+// Also, sometimes we want to have a fallback
+// Pass in a callback to wait for the fallback on failures
+// After the first lookup, always returns the same thing.
+function memo (key, lookup, fallback) {
+  var fell = false
+  var falling = false
+  exports[key] = function (cb) {
+    var val = lookup()
+    if (!val && !fell && !falling && fallback) {
+      fell = true
+      falling = true
+      exec(fallback, function (er, output, stderr) {
+        falling = false
+        if (er) return // oh well, we tried
+        val = output.trim()
+      })
+    }
+    exports[key] = function (cb) {
+      if (cb) process.nextTick(cb.bind(null, null, val))
+      return val
+    }
+    if (cb && !falling) process.nextTick(cb.bind(null, null, val))
+    return val
+  }
+}
+
+memo('user', function () {
+  return ( isWindows
+         ? process.env.USERDOMAIN + '\\' + process.env.USERNAME
+         : process.env.USER
+         )
+}, 'whoami')
+
+memo('prompt', function () {
+  return isWindows ? process.env.PROMPT : process.env.PS1
+})
+
+memo('hostname', function () {
+  return isWindows ? process.env.COMPUTERNAME : process.env.HOSTNAME
+}, 'hostname')
+
+memo('tmpdir', function () {
+  var t = isWindows ? 'temp' : 'tmp'
+  return process.env.TMPDIR ||
+         process.env.TMP ||
+         process.env.TEMP ||
+         ( exports.home() ? path.resolve(exports.home(), t)
+         : isWindows ? path.resolve(windir, t)
+         : '/tmp'
+         )
+})
+
+memo('home', function () {
+  return ( isWindows ? process.env.USERPROFILE
+         : process.env.HOME
+         )
+})
+
+memo('path', function () {
+  return (process.env.PATH ||
+          process.env.Path ||
+          process.env.path).split(isWindows ? ';' : ':')
+})
+

test/unix.js

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+// only run this test on windows
+// pretending to be another platform is too hacky, since it breaks
+// how the underlying system looks up module paths and runs
+// child processes, and all that stuff is cached.
+if (process.platform === 'win32') {
+  console.log('TAP Version 13\n' +
+              '1..0\n' +
+              '# Skip unix tests, this is not unix\n')
+  return
+}
+var tap = require('tap')
+
+// like unix, but funny
+process.env.USER = 'sirUser'
+process.env.HOME = '/home/sirUser'
+process.env.HOSTNAME = 'my-machine'
+process.env.TMPDIR = '/tmpdir'
+process.env.TMP = '/tmp'
+process.env.TEMP = '/temp'
+process.env.PATH = '/opt/local/bin:/usr/local/bin:/usr/bin/:bin'
+process.env.PS1 = '(o_o) $ '
+
+
+tap.test('basic unix sanity test', function (t) {
+  var osenv = require('../osenv.js')
+
+  t.equal(osenv.user(), process.env.USER)
+  t.equal(osenv.home(), process.env.HOME)
+  t.equal(osenv.hostname(), process.env.HOSTNAME)
+  t.same(osenv.path(), process.env.PATH.split(':'))
+  t.equal(osenv.prompt(), process.env.PS1)
+  t.equal(osenv.tmpdir(), process.env.TMPDIR)
+
+  // mildly evil, but it's for a test.
+  process.env.TMPDIR = ''
+  delete require.cache[require.resolve('../osenv.js')]
+  var osenv = require('../osenv.js')
+  t.equal(osenv.tmpdir(), process.env.TMP)
+
+  process.env.TMP = ''
+  delete require.cache[require.resolve('../osenv.js')]
+  var osenv = require('../osenv.js')
+  t.equal(osenv.tmpdir(), process.env.TEMP)
+
+  process.env.TEMP = ''
+  delete require.cache[require.resolve('../osenv.js')]
+  var osenv = require('../osenv.js')
+  console.error('osenv.home', osenv.home())
+  t.equal(osenv.tmpdir(), '/home/sirUser/tmp')
+
+  delete require.cache[require.resolve('../osenv.js')]
+  var osenv = require('../osenv.js')
+  osenv.home = function () { return null }
+  t.equal(osenv.tmpdir(), '/tmp')
+
+  t.end()
+})

test/windows.js

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+// only run this test on windows
+// pretending to be another platform is too hacky, since it breaks
+// how the underlying system looks up module paths and runs
+// child processes, and all that stuff is cached.
+if (process.platform !== 'win32') {
+  console.log('TAP Version 13\n' +
+              '1..0\n' +
+              '# Skip windows tests, this is not windows\n')
+  return
+}
+
+// load this before clubbing the platform name.
+var tap = require('tap')
+
+process.env.windir = 'C:\\windows'
+process.env.USERDOMAIN = 'some-domain'
+process.env.USERNAME = 'sirUser'
+process.env.USERPROFILE = 'C:\\Users\\sirUser'
+process.env.COMPUTERNAME = 'my-machine'
+process.env.TMPDIR = 'C:\\tmpdir'
+process.env.TMP = 'C:\\tmp'
+process.env.TEMP = 'C:\\temp'
+process.env.Path = 'C:\\Program Files\\;C:\\Binary Stuff\\bin'
+process.env.PROMPT = '(o_o) $ '
+
+tap.test('basic windows sanity test', function (t) {
+  var osenv = require('../osenv.js')
+
+  var osenv = require('../osenv.js')
+
+  t.equal(osenv.user(),
+          process.env.USERDOMAIN + '\\' + process.env.USERNAME)
+  t.equal(osenv.home(), process.env.USERPROFILE)
+  t.equal(osenv.hostname(), process.env.COMPUTERNAME)
+  t.same(osenv.path(), process.env.Path.split(';'))
+  t.equal(osenv.prompt(), process.env.PROMPT)
+  t.equal(osenv.tmpdir(), process.env.TMPDIR)
+
+  // mildly evil, but it's for a test.
+  process.env.TMPDIR = ''
+  delete require.cache[require.resolve('../osenv.js')]
+  var osenv = require('../osenv.js')
+  t.equal(osenv.tmpdir(), process.env.TMP)
+
+  process.env.TMP = ''
+  delete require.cache[require.resolve('../osenv.js')]
+  var osenv = require('../osenv.js')
+  t.equal(osenv.tmpdir(), process.env.TEMP)
+
+  process.env.TEMP = ''
+  delete require.cache[require.resolve('../osenv.js')]
+  var osenv = require('../osenv.js')
+  t.equal(osenv.tmpdir(), 'C:\\Users\\sirUser\\temp')
+
+  process.env.TEMP = ''
+  delete require.cache[require.resolve('../osenv.js')]
+  var osenv = require('../osenv.js')
+  osenv.home = function () { return null }
+  t.equal(osenv.tmpdir(), 'C:\\windows\\temp')
+
+  t.end()
+})