FIX: Explicit check for empty string in compat migration (#463)

db/post_migrate/20240207144910_fix_llm_backed_setting_defaults.rb

@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+
+# Some sites defaults weren't migrated correctly due to the previous migration
+# using the value as the if condition instead of checking with String#empty?
+class FixLlmBackedSettingDefaults < ActiveRecord::Migration[7.0]
+  def up
+    backfill_settings("composer_ai_helper_enabled", "ai_helper_model")
+    backfill_settings(
+      "ai_embeddings_semantic_search_enabled",
+      "ai_embeddings_semantic_search_hyde_model",
+    )
+  end
+
+  def down
+    raise ActiveRecord::IrreversibleMigration
+  end
+
+  def backfill_settings(feature_setting_name, llm_setting_name)
+    feature_enabled =
+      DB.query_single(
+        "SELECT value FROM site_settings WHERE name = :setting_name",
+        setting_name: feature_setting_name,
+      ).first == "t"
+
+    setting_value =
+      DB
+        .query_single(
+          "SELECT value FROM site_settings WHERE name = :llm_setting",
+          llm_setting: llm_setting_name,
+        )
+        .first
+        .to_s
+    using_old_default = setting_value.empty?
+
+    providers = %w[aws_bedrock anthropic open_ai hugging_face vllm google]
+    # Sanity check to make sure we won't add provider twice.
+    return if providers.include?(setting_value.split(":").first)
+
+    if using_old_default && feature_enabled
+      # Enabled and using old default (gpt-3.5-turbo)
+      DB.exec(<<~SQL, llm_setting: llm_setting_name, default: "open_ai:gpt-3.5-turbo")
+        INSERT INTO site_settings(name, data_type, value, created_at, updated_at)
+        VALUES (:llm_setting, 1, :default, NOW(), NOW())
+      SQL
+    end
+  end
+end