FIX: Include Symbol polyfill for IE11

This is necessary when we use `for (x of y)` operators in Javascript as
they are transpiled to use `Symbol` which is not present in IE.

plugins/discourse-internet-explorer/public/js/ie.js

@@ -357,4 +357,642 @@ if (!String.prototype.repeat) {
   };
 }
 
+/*!
+ * Symbol-ES6 v0.1.2
+ * ES6 Symbol polyfill in pure ES5.
+ *
+ * @license Copyright (c) 2017-2018 Rousan Ali, MIT License
+ *
+ * Codebase: https://github.com/rousan/symbol-es6
+ * Date: 28th Jan, 2018
+ */
+
+(function(global, factory) {
+  "use strict";
+
+  if (typeof module === "object" && typeof module.exports === "object") {
+    // For the environment like NodeJS, CommonJS etc where module or
+    // module.exports objects are available
+    module.exports = factory(global);
+  } else {
+    // For browser context, where global object is window
+    factory(global);
+  }
+
+  /* window is for browser environment and global is for NodeJS environment */
+})(typeof window !== "undefined" ? window : global, function(global) {
+  "use strict";
+
+  var defineProperty = Object.defineProperty;
+
+  var defineProperties = Object.defineProperties;
+
+  var symbolHiddenCounter = 0;
+
+  var globalSymbolRegistry = [];
+
+  var slice = Array.prototype.slice;
+
+  var ES6 = typeof global.ES6 === "object" ? global.ES6 : (global.ES6 = {});
+
+  var isArray = Array.isArray;
+
+  var objectToString = Object.prototype.toString;
+
+  var push = Array.prototype.push;
+
+  var emptyFunction = function() {};
+
+  var simpleFunction = function(arg) {
+    return arg;
+  };
+
+  var isCallable = function(fn) {
+    return typeof fn === "function";
+  };
+
+  var isConstructor = function(fn) {
+    return isCallable(fn);
+  };
+
+  var Iterator = function() {};
+
+  var ArrayIterator = function ArrayIterator(array, flag) {
+    this._array = array;
+    this._flag = flag;
+    this._nextIndex = 0;
+  };
+
+  var StringIterator = function StringIterator(string, flag) {
+    this._string = string;
+    this._flag = flag;
+    this._nextIndex = 0;
+  };
+
+  var isES6Running = function() {
+    return false; /* Now 'false' for testing purpose */
+  };
+
+  var isObject = function(value) {
+    return (
+      value !== null &&
+      (typeof value === "object" || typeof value === "function")
+    );
+  };
+
+  var es6FunctionPrototypeHasInstanceSymbol = function(instance) {
+    if (typeof this !== "function") return false;
+    return instance instanceof this;
+  };
+
+  var es6InstanceOfOperator = function(object, constructor) {
+    if (!isObject(constructor))
+      throw new TypeError("Right-hand side of 'instanceof' is not an object");
+
+    var hasInstanceSymbolProp = constructor[Symbol.hasInstance];
+    if (typeof hasInstanceSymbolProp === "undefined") {
+      return object instanceof constructor;
+    } else if (typeof hasInstanceSymbolProp !== "function") {
+      throw new TypeError(typeof hasInstanceSymbolProp + " is not a function");
+    } else {
+      return hasInstanceSymbolProp.call(constructor, object);
+    }
+  };
+
+  // Generates name for a symbol instance and this name will be used as
+  // property key for property symbols internally.
+  var generateSymbolName = function(id) {
+    return "@@_____" + id + "_____";
+  };
+
+  // Generates id for next Symbol instance
+  var getNextSymbolId = function() {
+    return symbolHiddenCounter++;
+  };
+
+  var setupSymbolInternals = function(symbol, desc) {
+    defineProperties(symbol, {
+      _description: {
+        value: desc
+      },
+      _isSymbol: {
+        value: true
+      },
+      _id: {
+        value: getNextSymbolId()
+      }
+    });
+    return symbol;
+  };
+
+  var checkSymbolInternals = function(symbol) {
+    return (
+      symbol._isSymbol === true &&
+      typeof symbol._id === "number" &&
+      typeof symbol._description === "string"
+    );
+  };
+
+  var isSymbol = function(symbol) {
+    return symbol instanceof Symbol && checkSymbolInternals(symbol);
+  };
+
+  var symbolFor = function(key) {
+    key = String(key);
+    var registryLength = globalSymbolRegistry.length,
+      record,
+      i = 0;
+
+    for (; i < registryLength; ++i) {
+      record = globalSymbolRegistry[i];
+      if (record.key === key) return record.symbol;
+    }
+
+    record = {
+      key: key,
+      symbol: Symbol(key)
+    };
+    globalSymbolRegistry.push(record);
+    return record.symbol;
+  };
+
+  var symbolKeyFor = function(symbol) {
+    if (!ES6.isSymbol(symbol))
+      throw new TypeError(String(symbol) + " is not a symbol");
+    var registryLength = globalSymbolRegistry.length,
+      record,
+      i = 0;
+
+    for (; i < registryLength; ++i) {
+      record = globalSymbolRegistry[i];
+      if (record.symbol === symbol) return record.key;
+    }
+  };
+
+  /* It affects array1 and appends array2 at the end of array1 */
+  var appendArray = function(array1, array2) {
+    // Returns immediately if these are not array or not array-like objects
+    if (
+      !(
+        typeof array1.length === "number" &&
+        array1.length >= 0 &&
+        typeof array2.length === "number" &&
+        array2.length >= 0
+      )
+    )
+      return;
+    var length1 = Math.floor(array1.length),
+      length2 = Math.floor(array2.length),
+      i = 0;
+
+    array1.length = length1 + length2;
+    for (; i < length2; ++i)
+      if (array2.hasOwnProperty(i)) array1[length1 + i] = array2[i];
+  };
+
+  var es6ObjectPrototypeToString = function toString() {
+    if (this === undefined || this === null) return objectToString.call(this);
+    // Add support for @@toStringTag symbol
+    if (typeof this[Symbol.toStringTag] === "string")
+      return "[object " + this[Symbol.toStringTag] + "]";
+    else return objectToString.call(this);
+  };
+
+  var es6ArrayPrototypeConcat = function concat() {
+    if (this === undefined || this === null)
+      throw new TypeError("Array.prototype.concat called on null or undefined");
+
+    // Boxing 'this' value to wrapper object
+    var self = Object(this),
+      targets = slice.call(arguments),
+      outputs = []; // Later it may affected by Symbol
+
+    targets.unshift(self);
+
+    targets.forEach(function(target) {
+      // If target is primitive then just push
+      if (!isObject(target)) outputs.push(target);
+      // Here Symbol.isConcatSpreadable support is added
+      else if (typeof target[Symbol.isConcatSpreadable] !== "undefined") {
+        if (target[Symbol.isConcatSpreadable]) {
+          appendArray(outputs, target);
+        } else {
+          outputs.push(target);
+        }
+      } else if (isArray(target)) {
+        appendArray(outputs, target);
+      } else {
+        outputs.push(target);
+      }
+    });
+    return outputs;
+  };
+
+  var es6ForOfLoop = function(iterable, callback, thisArg) {
+    callback = typeof callback !== "function" ? emptyFunction : callback;
+    if (typeof iterable[Symbol.iterator] !== "function")
+      throw new TypeError("Iterable[Symbol.iterator] is not a function");
+    var iterator = iterable[Symbol.iterator](),
+      iterationResult;
+    if (typeof iterator.next !== "function")
+      throw new TypeError(".iterator.next is not a function");
+    while (true) {
+      iterationResult = iterator.next();
+      if (!isObject(iterationResult))
+        throw new TypeError(
+          "Iterator result " + iterationResult + " is not an object"
+        );
+      if (iterationResult.done) break;
+      callback.call(thisArg, iterationResult.value);
+    }
+  };
+
+  // Provides simple inheritance functionality
+  var simpleInheritance = function(child, parent) {
+    if (typeof child !== "function" || typeof parent !== "function")
+      throw new TypeError("Child and Parent must be function type");
+
+    child.prototype = Object.create(parent.prototype);
+    child.prototype.constructor = child;
+  };
+
+  // Behaves as Symbol function in ES6, take description and returns an unique object,
+  // but in ES6 this function returns 'symbol' primitive typed value.
+  // Its type is 'object' not 'symbol'.
+  // There is no wrapping in this case i.e. Object(sym) = sym.
+  var Symbol = function Symbol(desc) {
+    desc = typeof desc === "undefined" ? "" : String(desc);
+
+    if (this instanceof Symbol)
+      throw new TypeError("Symbol is not a constructor");
+
+    return setupSymbolInternals(Object.create(Symbol.prototype), desc);
+  };
+
+  defineProperties(Symbol, {
+    for: {
+      value: symbolFor,
+      writable: true,
+      configurable: true
+    },
+
+    keyFor: {
+      value: symbolKeyFor,
+      writable: true,
+      configurable: true
+    },
+
+    hasInstance: {
+      value: Symbol("Symbol.hasInstance")
+    },
+
+    isConcatSpreadable: {
+      value: Symbol("Symbol.isConcatSpreadable")
+    },
+
+    iterator: {
+      value: Symbol("Symbol.iterator")
+    },
+
+    toStringTag: {
+      value: Symbol("Symbol.toStringTag")
+    }
+  });
+
+  // In ES6, this function returns like 'Symbol(<desc>)', but in this case
+  // this function returns the symbol's internal name to work properly.
+  Symbol.prototype.toString = function() {
+    return generateSymbolName(this._id);
+  };
+
+  // Returns itself but in ES6 It returns 'symbol' typed value.
+  Symbol.prototype.valueOf = function() {
+    return this;
+  };
+
+  // Make Iterator like iterable
+  defineProperty(Iterator.prototype, Symbol.iterator.toString(), {
+    value: function() {
+      return this;
+    },
+    writable: true,
+    configurable: true
+  });
+
+  simpleInheritance(ArrayIterator, Iterator);
+
+  simpleInheritance(StringIterator, Iterator);
+
+  defineProperty(ArrayIterator.prototype, Symbol.toStringTag.toString(), {
+    value: "Array Iterator",
+    configurable: true
+  });
+
+  defineProperty(StringIterator.prototype, Symbol.toStringTag.toString(), {
+    value: "String Iterator",
+    configurable: true
+  });
+
+  // This iterator works on any Array or TypedArray or array-like objects
+  ArrayIterator.prototype.next = function next() {
+    if (!(this instanceof ArrayIterator))
+      throw new TypeError(
+        "Method Array Iterator.prototype.next called on incompatible receiver " +
+          String(this)
+      );
+
+    var self = this,
+      nextValue;
+
+    if (self._nextIndex === -1) {
+      return {
+        done: true,
+        value: undefined
+      };
+    }
+
+    if (!(typeof self._array.length === "number" && self._array.length >= 0)) {
+      self._nextIndex = -1;
+      return {
+        done: true,
+        value: undefined
+      };
+    }
+
+    // _flag = 1 for [index, value]
+    // _flag = 2 for [value]
+    // _flag = 3 for [index]
+    if (self._nextIndex < Math.floor(self._array.length)) {
+      if (self._flag === 1)
+        nextValue = [self._nextIndex, self._array[self._nextIndex]];
+      else if (self._flag === 2) nextValue = self._array[self._nextIndex];
+      else if (self._flag === 3) nextValue = self._nextIndex;
+      self._nextIndex++;
+      return {
+        done: false,
+        value: nextValue
+      };
+    } else {
+      self._nextIndex = -1;
+      return {
+        done: true,
+        value: undefined
+      };
+    }
+  };
+
+  StringIterator.prototype.next = function next() {
+    if (!(this instanceof StringIterator))
+      throw new TypeError(
+        "Method String Iterator.prototype.next called on incompatible receiver " +
+          String(this)
+      );
+
+    var self = this,
+      stringObject = new String(this._string),
+      nextValue;
+
+    if (self._nextIndex === -1) {
+      return {
+        done: true,
+        value: undefined
+      };
+    }
+
+    if (self._nextIndex < stringObject.length) {
+      nextValue = stringObject[self._nextIndex];
+      self._nextIndex++;
+      return {
+        done: false,
+        value: nextValue
+      };
+    } else {
+      self._nextIndex = -1;
+      return {
+        done: true,
+        value: undefined
+      };
+    }
+  };
+
+  var es6ArrayPrototypeIteratorSymbol = function values() {
+    if (this === undefined || this === null)
+      throw new TypeError("Cannot convert undefined or null to object");
+
+    var self = Object(this);
+    return new ArrayIterator(self, 2);
+  };
+
+  var es6StringPrototypeIteratorSymbol = function values() {
+    if (this === undefined || this === null)
+      throw new TypeError(
+        "String.prototype[Symbol.iterator] called on null or undefined"
+      );
+    return new StringIterator(String(this), 0);
+  };
+
+  var es6ArrayPrototypeEntries = function entries() {
+    if (this === undefined || this === null)
+      throw new TypeError("Cannot convert undefined or null to object");
+
+    var self = Object(this);
+    return new ArrayIterator(self, 1);
+  };
+
+  var es6ArrayPrototypeKeys = function keys() {
+    if (this === undefined || this === null)
+      throw new TypeError("Cannot convert undefined or null to object");
+    var self = Object(this);
+    return new ArrayIterator(self, 3);
+  };
+
+  var SpreadOperatorImpl = function(target, thisArg) {
+    this._target = target;
+    this._values = [];
+    this._thisArg = thisArg;
+  };
+  // All the arguments must be iterable
+  SpreadOperatorImpl.prototype.spread = function() {
+    var self = this;
+    slice.call(arguments).forEach(function(iterable) {
+      ES6.forOf(iterable, function(value) {
+        self._values.push(value);
+      });
+    });
+    return self;
+  };
+
+  SpreadOperatorImpl.prototype.add = function() {
+    var self = this;
+    slice.call(arguments).forEach(function(value) {
+      self._values.push(value);
+    });
+    return self;
+  };
+
+  SpreadOperatorImpl.prototype.call = function(thisArg) {
+    if (typeof this._target !== "function")
+      throw new TypeError("Target is not a function");
+    thisArg = arguments.length <= 0 ? this._thisArg : thisArg;
+    return this._target.apply(thisArg, this._values);
+  };
+
+  SpreadOperatorImpl.prototype.new = function() {
+    if (typeof this._target !== "function")
+      throw new TypeError("Target is not a constructor");
+
+    var temp, returnValue;
+    temp = Object.create(this._target.prototype);
+    returnValue = this._target.apply(temp, this._values);
+    return isObject(returnValue) ? returnValue : temp;
+  };
+
+  // Affects the target array
+  SpreadOperatorImpl.prototype.array = function() {
+    if (!isArray(this._target)) throw new TypeError("Target is not a array");
+    push.apply(this._target, this._values);
+    return this._target;
+  };
+
+  // Target must be Array or function
+  var es6SpreadOperator = function spreadOperator(target, thisArg) {
+    if (!(typeof target === "function" || isArray(target)))
+      throw new TypeError(
+        "Spread operator only supports on array and function objects at this moment"
+      );
+    return new SpreadOperatorImpl(target, thisArg);
+  };
+
+  var es6ArrayFrom = function from(arrayLike, mapFn, thisArg) {
+    var constructor,
+      i = 0,
+      length,
+      outputs;
+    // Use the generic constructor
+    constructor = !isConstructor(this) ? Array : this;
+    if (arrayLike === undefined || arrayLike === null)
+      throw new TypeError("Cannot convert undefined or null to object");
+
+    arrayLike = Object(arrayLike);
+    if (mapFn === undefined) mapFn = simpleFunction;
+    else if (!isCallable(mapFn))
+      throw new TypeError(mapFn + " is not a function");
+
+    if (typeof arrayLike[Symbol.iterator] === "undefined") {
+      if (!(typeof arrayLike.length === "number" && arrayLike.length >= 0)) {
+        outputs = new constructor(0);
+        outputs.length = 0;
+        return outputs;
+      }
+      length = Math.floor(arrayLike.length);
+      outputs = new constructor(length);
+      outputs.length = length;
+      for (; i < length; ++i) outputs[i] = mapFn.call(thisArg, arrayLike[i]);
+    } else {
+      outputs = new constructor();
+      outputs.length = 0;
+      ES6.forOf(arrayLike, function(value) {
+        outputs.length++;
+        outputs[outputs.length - 1] = mapFn.call(thisArg, value);
+      });
+    }
+    return outputs;
+  };
+
+  // Export ES6 APIs and add all the patches to support Symbol in ES5
+  // If the running environment already supports ES6 then no patches will be applied,
+  if (isES6Running()) return ES6;
+  else {
+    // Some ES6 APIs can't be implemented in pure ES5, so this 'ES6' object provides
+    // some equivalent functionality of these features.
+    defineProperties(ES6, {
+      // Checks if a JS value is a symbol
+      // It can be used as equivalent api in ES6: typeof symbol === 'symbol'
+      isSymbol: {
+        value: isSymbol,
+        writable: true,
+        configurable: true
+      },
+
+      // Native ES5 'instanceof' operator does not support @@hasInstance symbol,
+      // this method provides same functionality of ES6 'instanceof' operator.
+      instanceOf: {
+        value: es6InstanceOfOperator,
+        writable: true,
+        configurable: true
+      },
+
+      // This method behaves exactly same as ES6 for...of loop.
+      forOf: {
+        value: es6ForOfLoop,
+        writable: true,
+        configurable: true
+      },
+
+      // This method gives same functionality of the spread operator of ES6
+      // It works on only functions and arrays.
+      // Limitation: You can't create array like this [...iterable, , , , 33] by this method,
+      // to achieve this you have to do like this [...iterable, undefined, undefined, undefined, 33]
+      spreadOperator: {
+        value: es6SpreadOperator,
+        writable: true,
+        configurable: true
+      }
+    });
+
+    defineProperty(global, "Symbol", {
+      value: Symbol,
+      writable: true,
+      configurable: true
+    });
+
+    defineProperty(Function.prototype, Symbol.hasInstance.toString(), {
+      value: es6FunctionPrototypeHasInstanceSymbol
+    });
+
+    defineProperty(Array.prototype, "concat", {
+      value: es6ArrayPrototypeConcat,
+      writable: true,
+      configurable: true
+    });
+
+    defineProperty(Object.prototype, "toString", {
+      value: es6ObjectPrototypeToString,
+      writable: true,
+      configurable: true
+    });
+
+    defineProperty(Array.prototype, Symbol.iterator.toString(), {
+      value: es6ArrayPrototypeIteratorSymbol,
+      writable: true,
+      configurable: true
+    });
+
+    defineProperty(Array, "from", {
+      value: es6ArrayFrom,
+      writable: true,
+      configurable: true
+    });
+
+    defineProperty(Array.prototype, "entries", {
+      value: es6ArrayPrototypeEntries,
+      writable: true,
+      configurable: true
+    });
+
+    defineProperty(Array.prototype, "keys", {
+      value: es6ArrayPrototypeKeys,
+      writable: true,
+      configurable: true
+    });
+
+    defineProperty(String.prototype, Symbol.iterator.toString(), {
+      value: es6StringPrototypeIteratorSymbol,
+      writable: true,
+      configurable: true
+    });
+  }
+
+  return ES6;
+});
 /* eslint-enable */