os: refactor os structure, add Symbol.toPrimitive

Refactor the structure of the os module to use more efficient
module.exports = {} pattern.

Add Symbol.toPrimitive support to os methods that return simple
primitives. This is a minor tweak that makes using these slightly
more friendly when doing things like:

```js
var m = `${os.tmpdir}/foo`
```

PR-URL: https://github.com/nodejs/node/pull/12654
Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>
Reviewed-By: Alexey Orlenko <eaglexrlnk@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>

lib/os.js

@@ -21,31 +21,50 @@
 
 'use strict';
 
-const binding = process.binding('os');
-const getCPUs = binding.getCPUs;
-const getLoadAvg = binding.getLoadAvg;
 const pushValToArrayMax = process.binding('util').pushValToArrayMax;
 const constants = process.binding('constants').os;
-const internalUtil = require('internal/util');
+const deprecate = require('internal/util').deprecate;
 const isWindows = process.platform === 'win32';
 
-exports.hostname = binding.getHostname;
-exports.uptime = binding.getUptime;
-exports.freemem = binding.getFreeMem;
-exports.totalmem = binding.getTotalMem;
-exports.type = binding.getOSType;
-exports.release = binding.getOSRelease;
-exports.networkInterfaces = binding.getInterfaceAddresses;
-exports.homedir = binding.getHomeDirectory;
-exports.userInfo = binding.getUserInfo;
+const {
+  getCPUs,
+  getFreeMem,
+  getHomeDirectory,
+  getHostname,
+  getInterfaceAddresses,
+  getLoadAvg,
+  getOSRelease,
+  getOSType,
+  getTotalMem,
+  getUserInfo,
+  getUptime,
+  isBigEndian
+} = process.binding('os');
+
+getFreeMem[Symbol.toPrimitive] = () => getFreeMem();
+getHostname[Symbol.toPrimitive] = () => getHostname();
+getHomeDirectory[Symbol.toPrimitive] = () => getHomeDirectory();
+getOSRelease[Symbol.toPrimitive] = () => getOSRelease();
+getOSType[Symbol.toPrimitive] = () => getOSType();
+getTotalMem[Symbol.toPrimitive] = () => getTotalMem();
+getUptime[Symbol.toPrimitive] = () => getUptime();
+
+const kEndianness = isBigEndian ? 'BE' : 'LE';
+
+const tmpDirDeprecationMsg =
+  'os.tmpDir() is deprecated. Use os.tmpdir() instead.';
+
+const getNetworkInterfacesDepMsg =
+  'os.getNetworkInterfaces is deprecated. Use os.networkInterfaces instead.';
 
 const avgValues = new Float64Array(3);
-exports.loadavg = function loadavg() {
+const cpuValues = new Float64Array(6 * pushValToArrayMax);
+
+function loadavg() {
   getLoadAvg(avgValues);
   return [avgValues[0], avgValues[1], avgValues[2]];
-};
+}
 
-const cpuValues = new Float64Array(6 * pushValToArrayMax);
 function addCPUInfo() {
   for (var i = 0, c = 0; i < arguments.length; ++i, c += 6) {
     this[this.length] = {
@@ -61,25 +80,22 @@ function addCPUInfo() {
     };
   }
 }
-exports.cpus = function cpus() {
-  return getCPUs(addCPUInfo, cpuValues, []);
-};
 
-Object.defineProperty(exports, 'constants', {
-  configurable: false,
-  enumerable: true,
-  value: constants
-});
+function cpus() {
+  return getCPUs(addCPUInfo, cpuValues, []);
+}
 
-exports.arch = function() {
+function arch() {
   return process.arch;
-};
+}
+arch[Symbol.toPrimitive] = () => process.arch;
 
-exports.platform = function() {
+function platform() {
   return process.platform;
-};
+}
+platform[Symbol.toPrimitive] = () => process.platform;
 
-exports.tmpdir = function() {
+function tmpdir() {
   var path;
   if (isWindows) {
     path = process.env.TEMP ||
@@ -97,22 +113,41 @@ exports.tmpdir = function() {
   }
 
   return path;
-};
+}
+tmpdir[Symbol.toPrimitive] = () => tmpdir();
 
-const tmpDirDeprecationMsg =
-  'os.tmpDir() is deprecated. Use os.tmpdir() instead.';
-exports.tmpDir = internalUtil.deprecate(exports.tmpdir,
-                                        tmpDirDeprecationMsg,
-                                        'DEP0022');
+function endianness() {
+  return kEndianness;
+}
+endianness[Symbol.toPrimitive] = () => kEndianness;
 
-exports.getNetworkInterfaces = internalUtil.deprecate(function() {
-  return exports.networkInterfaces();
-}, 'os.getNetworkInterfaces is deprecated. ' +
-   'Use os.networkInterfaces instead.', 'DEP0023');
+module.exports = exports = {
+  arch,
+  cpus,
+  EOL: isWindows ? '\r\n' : '\n',
+  endianness,
+  freemem: getFreeMem,
+  homedir: getHomeDirectory,
+  hostname: getHostname,
+  loadavg,
+  networkInterfaces: getInterfaceAddresses,
+  platform,
+  release: getOSRelease,
+  tmpdir,
+  totalmem: getTotalMem,
+  type: getOSType,
+  userInfo: getUserInfo,
+  uptime: getUptime,
 
-exports.EOL = isWindows ? '\r\n' : '\n';
+  // Deprecated APIs
+  getNetworkInterfaces: deprecate(getInterfaceAddresses,
+                                  getNetworkInterfacesDepMsg,
+                                  'DEP0023'),
+  tmpDir: deprecate(tmpdir, tmpDirDeprecationMsg, 'DEP0022')
+};
 
-if (binding.isBigEndian)
-  exports.endianness = function() { return 'BE'; };
-else
-  exports.endianness = function() { return 'LE'; };
+Object.defineProperty(module.exports, 'constants', {
+  configurable: false,
+  enumerable: true,
+  value: constants
+});

test/parallel/test-os.js

@@ -191,3 +191,12 @@ is.string(pwd.username);
 assert.ok(pwd.homedir.includes(path.sep));
 assert.strictEqual(pwd.username, pwdBuf.username.toString('utf8'));
 assert.strictEqual(pwd.homedir, pwdBuf.homedir.toString('utf8'));
+
+// Test that the Symbol.toPrimitive functions work correctly
+[
+  [`${os.hostname}`, os.hostname()],
+  [`${os.homedir}`, os.homedir()],
+  [`${os.release}`, os.release()],
+  [`${os.type}`, os.type()],
+  [`${os.endianness}`, os.endianness()]
+].forEach((set) => assert.strictEqual(set[0], set[1]));