`Ember.String.fmt` is deprecated

app/assets/javascripts/discourse/lib/computed.js.es6

@@ -1,3 +1,4 @@
+import addonFmt from 'ember-addons/fmt';
 /**
   Returns whether two properties are equal to each other.
 
@@ -46,14 +47,10 @@ export function propertyLessThan(p1, p2) {
   @params {String} format the i18n format string
   @return {Function} computedProperty function
 **/
-export function i18n() {
-  const args = Array.prototype.slice.call(arguments, 0);
+export function i18n(...args) {
   const format = args.pop();
-  const computed = Em.computed(function() {
-    const self = this;
-    return I18n.t(format.fmt.apply(format, args.map(function (a) {
-      return self.get(a);
-    })));
+  const computed = Ember.computed(function() {
+    return I18n.t(addonFmt(format, ...args.map(a => this.get(a))));
   });
   return computed.property.apply(computed, args);
 }
@@ -67,14 +64,10 @@ export function i18n() {
   @params {String} format the format string
   @return {Function} computedProperty function
 **/
-export function fmt() {
-  const args = Array.prototype.slice.call(arguments, 0);
+export function fmt(...args) {
   const format = args.pop();
-  const computed = Em.computed(function() {
-    const self = this;
-    return format.fmt.apply(format, args.map(function (a) {
-      return self.get(a);
-    }));
+  const computed = Ember.computed(function() {
+    return addonFmt(format, ...args.map(a => this.get(a)));
   });
   return computed.property.apply(computed, args);
 }
@@ -88,14 +81,10 @@ export function fmt() {
   @params {String} format the format string for the URL
   @return {Function} computedProperty function returning a URL
 **/
-export function url() {
-  const args = Array.prototype.slice.call(arguments, 0);
+export function url(...args) {
   const format = args.pop();
-  const computed = Em.computed(function() {
-    const self = this;
-    return Discourse.getURL(format.fmt.apply(format, args.map(function (a) {
-      return self.get(a);
-    })));
+  const computed = Ember.computed(function() {
+    return Discourse.getURL(addonFmt(format, ...args.map(a => this.get(a))));
   });
   return computed.property.apply(computed, args);
 }

app/assets/javascripts/ember-addons/fmt.js.es6

@@ -0,0 +1,24 @@
+import Ember from 'ember';
+
+const inspect = Ember.inspect;
+const isArray = Ember.isArray;
+
+export default function(str, formats) {
+  let cachedFormats = formats;
+
+  if (!isArray(cachedFormats) || arguments.length > 2) {
+    cachedFormats = new Array(arguments.length - 1);
+
+    for (let i = 1, l = arguments.length; i < l; i++) {
+      cachedFormats[i - 1] = arguments[i];
+    }
+  }
+
+  // first, replace any ORDERED replacements.
+  let idx  = 0; // the current index for non-numerical replacements
+  return str.replace(/%@([0-9]+)?/g, function(s, argIndex) {
+    argIndex = (argIndex) ? parseInt(argIndex, 10) - 1 : idx++;
+    s = cachedFormats[argIndex];
+    return (s === null) ? '(null)' : (s === undefined) ? '' : inspect(s);
+  });
+}

app/assets/javascripts/main_include.js

@@ -2,6 +2,7 @@
 //= require ./ember-addons/decorator-alias
 //= require ./ember-addons/macro-alias
 //= require ./ember-addons/ember-computed-decorators
+//= require ./ember-addons/fmt
 //= require_tree ./discourse-common
 //= require ./discourse
 //= require ./deprecated