FIX: Do not allow blank chat messages (#21968)

This fixes an issue where a user could send an empty
string as a chat message .e.g '   ' and the message would
be posted. We don't want this, we need to strip the message
first before validating for length etc.

plugins/chat/app/models/chat/message.rb

@@ -76,6 +76,9 @@ module Chat
     def self.polymorphic_class_mapping = { "ChatMessage" => Chat::Message }
 
     def validate_message(has_uploads:)
+      self.message =
+        TextCleaner.clean(self.message, strip_whitespaces: true, strip_zero_width_spaces: true)
+
       WatchedWordsValidator.new(attributes: [:message]).validate(self)
 
       if self.new_record? || self.changed.include?("message")

plugins/chat/spec/components/chat/message_creator_spec.rb

@@ -65,6 +65,18 @@ describe Chat::MessageCreator do
       )
     end
 
+    it "errors when a blank message is sent" do
+      creator =
+        described_class.create(chat_channel: public_chat_channel, user: user1, content: "   ")
+      expect(creator.failed?).to eq(true)
+      expect(creator.error.message).to match(
+        I18n.t(
+          "chat.errors.minimum_length_not_met",
+          { count: SiteSetting.chat_minimum_message_length },
+        ),
+      )
+    end
+
     it "errors when length is greater than `chat_maximum_message_length`" do
       SiteSetting.chat_maximum_message_length = 100
       creator =

plugins/chat/spec/components/chat/message_updater_spec.rb

@@ -85,6 +85,27 @@ describe Chat::MessageUpdater do
     expect(chat_message.reload.message).to eq(og_message)
   end
 
+  it "errors when a blank message is sent" do
+    og_message = "This won't be changed!"
+    chat_message = create_chat_message(user1, og_message, public_chat_channel)
+    new_message = "    "
+
+    updater =
+      Chat::MessageUpdater.update(
+        guardian: guardian,
+        chat_message: chat_message,
+        new_content: new_message,
+      )
+    expect(updater.failed?).to eq(true)
+    expect(updater.error.message).to match(
+      I18n.t(
+        "chat.errors.minimum_length_not_met",
+        { count: SiteSetting.chat_minimum_message_length },
+      ),
+    )
+    expect(chat_message.reload.message).to eq(og_message)
+  end
+
   it "errors if a user other than the message user is trying to edit the message" do
     og_message = "This won't be changed!"
     chat_message = create_chat_message(user1, og_message, public_chat_channel)