FIX: Properly display error when post action fails to create.

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

@@ -3,6 +3,7 @@ import ActionSummary from "discourse/models/action-summary";
 import { MAX_MESSAGE_LENGTH } from "discourse/models/post-action-type";
 import computed from "ember-addons/ember-computed-decorators";
 import optionalService from "discourse/lib/optional-service";
+import { popupAjaxError } from "discourse/lib/ajax-error";
 
 export default Ember.Controller.extend(ModalFunctionality, {
   adminTools: optionalService(),
@@ -163,13 +164,9 @@ export default Ember.Controller.extend(ModalFunctionality, {
             id: this.get("model.id")
           });
         })
-        .catch(errors => {
+        .catch(error => {
           this.send("closeModal");
-          if (errors && errors.responseText) {
-            bootbox.alert($.parseJSON(errors.responseText).errors);
-          } else {
-            bootbox.alert(I18n.t("generic_error"));
-          }
+          popupAjaxError(error);
         });
     },
 

app/controllers/post_actions_controller.rb

@@ -26,7 +26,11 @@ class PostActionsController < ApplicationController
     args[:take_action] = true if guardian.is_staff? && params[:take_action] == 'true'
     args[:flag_topic] = true if params[:flag_topic] == 'true'
 
-    post_action = PostAction.act(current_user, @post, @post_action_type_id, args)
+    begin
+      post_action = PostAction.act(current_user, @post, @post_action_type_id, args)
+    rescue PostAction::FailedToCreatePost => e
+      return render_json_error(e.message)
+    end
 
     if post_action.blank? || post_action.errors.present?
       render_json_error(post_action)

app/models/post_action.rb

@@ -3,6 +3,7 @@ require_dependency 'system_message'
 
 class PostAction < ActiveRecord::Base
   class AlreadyActed < StandardError; end
+  class FailedToCreatePost < StandardError; end
 
   include RateLimiter::OnCreateRecord
   include Trashable
@@ -281,7 +282,12 @@ class PostAction < ActiveRecord::Base
   def self.act(user, post, post_action_type_id, opts = {})
     limit_action!(user, post, post_action_type_id)
 
-    related_post_id = create_message_for_post_action(user, post, post_action_type_id, opts)
+    begin
+      related_post_id = create_message_for_post_action(user, post, post_action_type_id, opts)
+    rescue ActiveRecord::RecordNotSaved => e
+      raise FailedToCreatePost.new(e.message)
+    end
+
     staff_took_action = opts[:take_action] || false
 
     targets_topic =

lib/post_creator.rb

@@ -205,7 +205,7 @@ class PostCreator
     create
 
     if !self.errors.full_messages.empty?
-      raise ActiveRecord::RecordNotSaved.new("Failed to create post: #{self.errors.full_messages}")
+      raise ActiveRecord::RecordNotSaved.new(self.errors.full_messages.to_sentence)
     end
 
     @post

spec/requests/post_actions_controller_spec.rb

@@ -87,7 +87,28 @@ RSpec.describe PostActionsController do
         post_action_type_id: PostActionType.types[:bookmark]
       }
 
-      expect(response).to be_forbidden
+      expect(response.status).to eq(403)
+    end
+
+    it 'fails when the user tries to notify user that has disabled PM' do
+      sign_in(Fabricate(:user))
+      user2 = Fabricate(:user)
+
+      post = Fabricate(:post, user: user2)
+      user2.user_option.update!(allow_private_messages: false)
+
+      post "/post_actions.json", params: {
+        id: post.id,
+        post_action_type_id: PostActionType.types[:notify_user],
+        message: 'testing',
+        flag_topic: false
+      }
+
+      expect(response.status).to eq(422)
+
+      expect(JSON.parse(response.body)["errors"].first).to eq(I18n.t(
+        :not_accepting_pms, username: user2.username
+      ))
     end
 
     describe 'as a moderator' do