Signup form: prefill username if Discourse Hub has a match for the email address. Also, fix some bad specs in username_checker_service_spec that were passing...

app/assets/javascripts/discourse/controllers/create_account_controller.js

@@ -15,6 +15,7 @@ Discourse.CreateAccountController = Discourse.Controller.extend(Discourse.ModalF
   accountChallenge: 0,
   formSubmitted: false,
   rejectedEmails: Em.A([]),
+  prefilledUsername: null,
 
   submitDisabled: function() {
     if (this.get('formSubmitted')) return true;
@@ -95,6 +96,28 @@ Discourse.CreateAccountController = Discourse.Controller.extend(Discourse.ModalF
     });
   }.property('accountEmail', 'rejectedEmails.@each'),
 
+  prefillUsername: function() {
+    if (this.get('prefilledUsername')) {
+      if (this.get('accountUsername') === this.get('prefilledUsername')) {
+        this.set('accountUsername', '');
+      }
+      this.set('prefilledUsername', null);
+    }
+    if (this.get('emailValidation.ok') && this.blank('accountUsername')) {
+      this.fetchExistingUsername();
+    }
+  }.observes('emailValidation', 'accountEmail'),
+
+  fetchExistingUsername: Discourse.debounce(function() {
+    var self = this;
+    Discourse.User.checkUsername(null, this.get('accountEmail')).then(function(result) {
+      if (result.suggestion && self.blank('accountUsername')) {
+        self.set('accountUsername', result.suggestion);
+        self.set('prefilledUsername', result.suggestion);
+      }
+    });
+  }, 500),
+
   usernameMatch: function() {
     if (this.usernameNeedsToBeValidatedWithEmail()) {
       if (this.get('emailValidation.failed')) {
@@ -119,6 +142,13 @@ Discourse.CreateAccountController = Discourse.Controller.extend(Discourse.ModalF
   basicUsernameValidation: function() {
     this.set('uniqueUsernameValidation', null);
 
+    if (this.get('accountUsername') === this.get('prefilledUsername')) {
+      return Discourse.InputValidation.create({
+        ok: true,
+        reason: I18n.t('user.username.prefilled')
+      });
+    }
+
     // If blank, fail without a reason
     if (this.blank('accountUsername')) {
       return Discourse.InputValidation.create({

app/controllers/users_controller.rb

@@ -97,7 +97,10 @@ class UsersController < ApplicationController
   # Used for checking availability of a username and will return suggestions
   # if the username is not available.
   def check_username
-    params.require(:username)
+    if !params[:username].present?
+      params.require(:username) if !params[:email].present?
+      return render(json: success_json) unless SiteSetting.call_discourse_hub?
+    end
     username = params[:username]
 
     target_user = user_from_params_or_current_user
@@ -107,7 +110,7 @@ class UsersController < ApplicationController
 
     checker = UsernameCheckerService.new
     email = params[:email] || target_user.try(:email)
-    render(json: checker.check_username(username, email))
+    render json: checker.check_username(username, email)
   rescue RestClient::Forbidden
     render json: {errors: [I18n.t("discourse_hub.access_token_problem")]}
   end

app/services/username_checker_service.rb

@@ -1,15 +1,18 @@
 class UsernameCheckerService
 
   def check_username(username, email)
-    validator = UsernameValidator.new(username)
-    if !validator.valid_format?
-      {errors: validator.errors}
-    elsif !SiteSetting.call_discourse_hub?
-      check_username_locally(username)
-    else
-      check_username_with_hub_server(username, email)
+    if username && username.length > 0
+      validator = UsernameValidator.new(username)
+      if !validator.valid_format?
+        {errors: validator.errors}
+      elsif !SiteSetting.call_discourse_hub?
+        check_username_locally(username)
+      else
+        check_username_with_hub_server(username, email)
+      end
+    elsif email and SiteSetting.call_discourse_hub?
+      {suggestion: DiscourseHub.nickname_for_email(email)}
     end
-
   end
 
   # Contact the Discourse Hub server