FIX: Avoid publishing post if there is no change (#140)

config/locales/server.en.yml

@@ -21,6 +21,8 @@ en:
     not_supported: "This language is not supported by the translator."
     too_long: "This post is too long to be translated by the translator."
     not_available: "The translator service is currently not available."
+    amazon:
+      invalid_credentials: "The provided credentials for AWS translate are invalid."
 
     microsoft:
       missing_token: "The translator was unable to retrieve a valid token."

plugin.rb

@@ -144,8 +144,10 @@ def execute(args)
 
         DistributedMutex.synchronize("detect_translation_#{post.id}") do
           "DiscourseTranslator::#{SiteSetting.translator}".constantize.detect(post)
-          post.save_custom_fields unless post.custom_fields_clean?
-          post.publish_change_to_clients! :revised
+          if !post.custom_fields_clean?
+            post.save_custom_fields
+            post.publish_change_to_clients! :revised
+          end
         end
       end
     end

services/discourse_translator/amazon.rb

@@ -105,16 +105,20 @@ def self.detect(topic_or_post)
 
       return if text.blank?
 
-      detected_lang =
-        client.translate_text(
-          {
-            text: text,
-            source_language_code: "auto",
-            target_language_code: SUPPORTED_LANG_MAPPING[I18n.locale],
-          },
-        )&.source_language_code
-
-      assign_lang_custom_field(topic_or_post, detected_lang)
+      begin
+        detected_lang =
+          client.translate_text(
+            {
+              text: text,
+              source_language_code: "auto",
+              target_language_code: SUPPORTED_LANG_MAPPING[I18n.locale],
+            },
+          )&.source_language_code
+
+        assign_lang_custom_field(topic_or_post, detected_lang)
+      rescue Aws::Errors::MissingCredentialsError
+        raise I18n.t("translator.amazon.invalid_credentials")
+      end
     end
 
     def self.translate(topic_or_post)

spec/jobs/detect_translation_spec.rb

@@ -37,9 +37,19 @@
     it "detects translation" do
       post = Fabricate(:post, raw: "this is a sample post")
 
-      Jobs::DetectTranslation.new.execute(post_id: post.id)
+      messages = MessageBus.track_publish { Jobs::DetectTranslation.new.execute(post_id: post.id) }
 
       expect(post.custom_fields[DiscourseTranslator::DETECTED_LANG_CUSTOM_FIELD]).to eq("en")
+      expect(messages.size).to eq(1)
+    end
+
+    it "does not publish change if no change in translation" do
+      post = Fabricate(:post, raw: "this is a sample post")
+      post.custom_fields[DiscourseTranslator::DETECTED_LANG_CUSTOM_FIELD] = "en"
+      post.save_custom_fields
+
+      messages = MessageBus.track_publish { Jobs::DetectTranslation.new.execute(post_id: post.id) }
+      expect(messages.size).to eq(0)
     end
   end
 end