FIX: :( page was never showing the URL

app/assets/javascripts/discourse/controllers/exception.js.es6

@@ -31,6 +31,7 @@ export default Ember.Controller.extend({
     if (this.get('thrown.jqTextStatus') === "timeout") return true;
     return false;
   }.property(),
+  isNotFound: Em.computed.equal('thrown.status', 404),
   isForbidden: Em.computed.equal('thrown.status', 403),
   isServer: Em.computed.gte('thrown.status', 500),
   isUnknown: Em.computed.none('isNetwork', 'isServer'),
@@ -50,6 +51,8 @@ export default Ember.Controller.extend({
       return I18n.t('errors.reasons.network');
     } else if (this.get('isServer')) {
       return I18n.t('errors.reasons.server');
+    } else if (this.get('isNotFound')) {
+      return I18n.t('errors.reasons.not_found');
     } else if (this.get('isForbidden')) {
       return I18n.t('errors.reasons.forbidden');
     } else {
@@ -65,6 +68,8 @@ export default Ember.Controller.extend({
       return I18n.t('errors.desc.network_fixed');
     } else if (this.get('isNetwork')) {
       return I18n.t('errors.desc.network');
+    } else if (this.get('isNotFound')) {
+      return I18n.t('errors.desc.not_found');
     } else if (this.get('isServer')) {
       return I18n.t('errors.desc.server', { status: this.get('thrown.status') + " " + this.get('thrown.statusText') });
     } else {

app/assets/javascripts/discourse/routes/application.js.es6

@@ -60,30 +60,24 @@ const ApplicationRoute = Discourse.Route.extend(OpenComposer, {
     },
 
     error(err, transition) {
-      if (err.status === 404) {
+      let xhr = {};
-        // 404
+      if (err.jqXHR) {
-        this.transitionTo('unknown');
+        xhr = err.jqXHR;
-        return;
       }
 
-      const exceptionController = this.controllerFor('exception'),
+      const xhrOrErr = err.jqXHR ? xhr : err;
-            stack = err.stack;
 
-      // If we have a stack call `toString` on it. It gives us a better
+      const exceptionController = this.controllerFor('exception');
-      // stack trace since `console.error` uses the stack track of this
-      // error callback rather than the original error.
-      let errorString = err.toString();
-      if (stack) { errorString = stack.toString(); }
-
-      if (err.statusText) { errorString = err.statusText; }
 
       const c = window.console;
       if (c && c.error) {
-        c.error(errorString);
+        c.error(xhrOrErr);
       }
-      exceptionController.setProperties({ lastTransition: transition, thrown: err });
+
+      exceptionController.setProperties({ lastTransition: transition, thrown: xhrOrErr });
 
       this.intermediateTransitionTo('exception');
+      return true;
     },
 
     showLogin: unlessReadOnly('handleShowLogin'),

config/locales/client.en.yml

@@ -684,11 +684,13 @@ en:
         server: "Server Error"
         forbidden: "Access Denied"
         unknown: "Error"
+        not_found: "Page Not Found"
       desc:
         network: "Please check your connection."
         network_fixed: "Looks like it's back."
         server: "Error code: {{status}}"
         forbidden: "You're not allowed to view that."
+        not_found: "Oops, the application tried to load a URL that doesn't exist."
         unknown: "Something went wrong."
       buttons:
         back: "Go Back"