UX: Display warning message about social logins disabled when 2FA is enabled.

app/assets/javascripts/discourse/controllers/preferences/second-factor.js.es6

@@ -1,6 +1,7 @@
 import { default as computed } from 'ember-addons/ember-computed-decorators';
 import { default as DiscourseURL, userPath } from 'discourse/lib/url';
 import { popupAjaxError } from 'discourse/lib/ajax-error';
+import { LOGIN_METHODS }  from 'discourse/models/login-method';
 
 export default Ember.Controller.extend({
   loading: false,
@@ -20,6 +21,13 @@ export default Ember.Controller.extend({
     return loading ? 'loading' : 'submit';
   },
 
+  @computed
+  displayOAuthWarning() {
+    return LOGIN_METHODS.some(name => {
+      return this.siteSettings[`enable_${name}_logins`];
+    });
+  },
+
   toggleSecondFactor(enable) {
     if (!this.get('secondFactorToken')) return;
     this.set('loading', true);

app/assets/javascripts/discourse/models/login-method.js.es6

@@ -22,19 +22,21 @@ const LoginMethod = Ember.Object.extend({
 let methods;
 let preRegister;
 
+export const LOGIN_METHODS = [
+  "google_oauth2",
+  "facebook",
+  "twitter",
+  "yahoo",
+  "instagram",
+  "github"
+];
+
 export function findAll(siteSettings, capabilities, isMobileDevice) {
   if (methods) { return methods; }
 
   methods = [];
 
-  [
-    "google_oauth2",
-    "facebook",
-    "twitter",
-    "yahoo",
-    "instagram",
-    "github"
-  ].forEach(name => {
+  LOGIN_METHODS.forEach(name => {
     if (siteSettings["enable_" + name + "_logins"]) {
       const params = { name };
       if (name === "google_oauth2") {

app/assets/javascripts/discourse/templates/preferences-second-factor.hbs

@@ -40,6 +40,10 @@
         <div class="control-group">
           <div class="controls">
             {{{i18n 'user.second_factor.enable_description'}}}
+
+            {{#if displayOAuthWarning}}
+              {{i18n 'user.second_factor.oauth_enabled_warning'}}
+            {{/if}}
           </div>
         </div>