DEV: Add debug lines for mystery no_user_selected error (#8759)

On some customer forums we are randomly getting a "You must select a valid user" error when sending a PM even when all parameters seem to be OK. This is an attempt to track it down with more data.

app/controllers/posts_controller.rb

@@ -777,6 +777,10 @@ class PostsController < ApplicationController
       result[:target_group_names] = groups.join(",")
     end
 
+    if recipients.blank? || result[:target_usernames].blank?
+      Rails.logger.debug("Missing recipients for PM! result: #{result.inspect} | params: #{params.inspect}")
+    end
+
     result.permit!
     result.to_h
   end

lib/topic_creator.rb

@@ -171,6 +171,8 @@ class TopicCreator
     topic.subtype = TopicSubtype.user_to_user unless topic.subtype
 
     unless @opts[:target_usernames].present? || @opts[:target_emails].present? || @opts[:target_group_names].present?
+      Rails.logger.debug("Topic PM cannot be created without recipients! opts: #{@opts.inspect}")
+
       rollback_with!(topic, :no_user_selected)
     end
 

spec/requests/posts_controller_spec.rb

@@ -1110,6 +1110,22 @@ describe PostsController do
         expect(new_topic.allowed_users).to contain_exactly(user, user_2, user_3)
       end
 
+      context "when target_recipients not provided" do
+        it "errors when creating a private post" do
+          post "/posts.json", params: {
+            raw: 'this is the test content',
+            archetype: 'private_message',
+            title: "this is some post",
+            target_recipients: ""
+          }
+
+          expect(response.status).to eq(422)
+          expect(JSON.parse(response.body)["errors"]).to include(
+            I18n.t("activerecord.errors.models.topic.attributes.base.no_user_selected")
+          )
+        end
+      end
+
       context "errors" do
         it "does not succeed" do
           post "/posts.json", params: { raw: 'test' }