lib: refactor internal/util

* Use the more efficient module.exports = {} approach
* Eliminate some uses of arguments

PR-URL: #11404
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net

lib/internal/util.js

@@ -5,19 +5,24 @@ const signals = process.binding('constants').os.signals;
 
 const kArrowMessagePrivateSymbolIndex = binding['arrow_message_private_symbol'];
 const kDecoratedPrivateSymbolIndex = binding['decorated_private_symbol'];
+const noCrypto = !process.versions.openssl;
 
-// The `buffer` module uses this. Defining it here instead of in the public
-// `util` module makes it accessible without having to `require('util')` there.
-exports.customInspectSymbol = Symbol('util.inspect.custom');
+function isError(e) {
+  return objectToString(e) === '[object Error]' || e instanceof Error;
+}
+
+function objectToString(o) {
+  return Object.prototype.toString.call(o);
+}
 
 // Mark that a method should not be used.
 // Returns a modified function which warns once by default.
 // If --no-deprecation is set, then it is a no-op.
-exports.deprecate = function deprecate(fn, msg, code) {
+function deprecate(fn, msg, code) {
   // Allow for deprecating things in the process of starting up.
   if (global.process === undefined) {
-    return function() {
-      return exports.deprecate(fn, msg, code).apply(this, arguments);
+    return function(...args) {
+      return deprecate(fn, msg).apply(this, args);
     };
   }
 
@@ -29,7 +34,7 @@ exports.deprecate = function deprecate(fn, msg, code) {
     throw new TypeError('`code` argument must be a string');
 
   var warned = false;
-  function deprecated() {
+  function deprecated(...args) {
     if (!warned) {
       warned = true;
       if (code !== undefined) {
@@ -39,9 +44,9 @@ exports.deprecate = function deprecate(fn, msg, code) {
       }
     }
     if (new.target) {
-      return Reflect.construct(fn, arguments, new.target);
+      return Reflect.construct(fn, args, new.target);
     }
-    return fn.apply(this, arguments);
+    return fn.apply(this, args);
   }
 
   // The wrapper will keep the same prototype as fn to maintain prototype chain
@@ -54,10 +59,10 @@ exports.deprecate = function deprecate(fn, msg, code) {
   }
 
   return deprecated;
-};
+}
 
-exports.decorateErrorStack = function decorateErrorStack(err) {
-  if (!(exports.isError(err) && err.stack) ||
+function decorateErrorStack(err) {
+  if (!(isError(err) && err.stack) ||
       binding.getHiddenValue(err, kDecoratedPrivateSymbolIndex) === true)
     return;
 
@@ -67,30 +72,19 @@ exports.decorateErrorStack = function decorateErrorStack(err) {
     err.stack = arrow + err.stack;
     binding.setHiddenValue(err, kDecoratedPrivateSymbolIndex, true);
   }
-};
-
-exports.isError = function isError(e) {
-  return exports.objectToString(e) === '[object Error]' || e instanceof Error;
-};
-
-exports.objectToString = function objectToString(o) {
-  return Object.prototype.toString.call(o);
-};
+}
 
-const noCrypto = !process.versions.openssl;
-exports.assertCrypto = function() {
+function assertCrypto() {
   if (noCrypto)
     throw new Error('Node.js is not compiled with openssl crypto support');
-};
-
-exports.kIsEncodingSymbol = Symbol('node.isEncoding');
+}
 
 // The loop should only run at most twice, retrying with lowercased enc
 // if there is no match in the first pass.
 // We use a loop instead of branching to retry with a helper
 // function in order to avoid the performance hit.
 // Return undefined if there is no match.
-exports.normalizeEncoding = function normalizeEncoding(enc) {
+function normalizeEncoding(enc) {
   if (!enc) return 'utf8';
   var retried;
   while (true) {
@@ -116,11 +110,9 @@ exports.normalizeEncoding = function normalizeEncoding(enc) {
         retried = true;
     }
   }
-};
+}
 
-// Filters duplicate strings. Used to support functions in crypto and tls
-// modules. Implemented specifically to maintain existing behaviors in each.
-exports.filterDuplicateStrings = function filterDuplicateStrings(items, low) {
+function filterDuplicateStrings(items, low) {
   const map = new Map();
   for (var i = 0; i < items.length; i++) {
     const item = items[i];
@@ -132,24 +124,24 @@ exports.filterDuplicateStrings = function filterDuplicateStrings(items, low) {
     }
   }
   return Array.from(map.values()).sort();
-};
+}
 
-exports.cachedResult = function cachedResult(fn) {
+function cachedResult(fn) {
   var result;
   return () => {
     if (result === undefined)
       result = fn();
     return result.slice();
   };
-};
+}
 
 // Useful for Wrapping an ES6 Class with a constructor Function that
 // does not require the new keyword. For instance:
 //   class A { constructor(x) {this.x = x;}}
 //   const B = createClassWrapper(A);
 //   B() instanceof A // true
 //   B() instanceof B // true
-exports.createClassWrapper = function createClassWrapper(type) {
+function createClassWrapper(type) {
   const fn = function(...args) {
     return Reflect.construct(type, args, new.target || type);
   };
@@ -161,7 +153,7 @@ exports.createClassWrapper = function createClassWrapper(type) {
   Object.setPrototypeOf(fn, type);
   fn.prototype = type.prototype;
   return fn;
-};
+}
 
 let signalsToNamesMapping;
 function getSignalsToNamesMapping() {
@@ -176,7 +168,7 @@ function getSignalsToNamesMapping() {
   return signalsToNamesMapping;
 }
 
-exports.convertToValidSignal = function convertToValidSignal(signal) {
+function convertToValidSignal(signal) {
   if (typeof signal === 'number' && getSignalsToNamesMapping()[signal])
     return signal;
 
@@ -186,4 +178,25 @@ exports.convertToValidSignal = function convertToValidSignal(signal) {
   }
 
   throw new Error('Unknown signal: ' + signal);
+}
+
+module.exports = exports = {
+  assertCrypto,
+  cachedResult,
+  convertToValidSignal,
+  createClassWrapper,
+  decorateErrorStack,
+  deprecate,
+  filterDuplicateStrings,
+  isError,
+  normalizeEncoding,
+  objectToString,
+
+  // Symbol used to provide a custom inspect function for an object as an
+  // alternative to using 'inspect'
+  customInspectSymbol: Symbol('util.inspect.custom'),
+
+  // Used by the buffer module to capture an internal reference to the
+  // default isEncoding implementation, just in case userland overrides it.
+  kIsEncodingSymbol: Symbol('node.isEncoding')
 };