Merge pull request rails#54713 from joshuay03/handle-libpq-server-version-0

Handle libpq db version 0 as connection failure in `PostgreSQLAdapter`

Author: byroot

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -634,7 +634,11 @@ def use_insert_returning?
       # Returns the version of the connected PostgreSQL server.
       def get_database_version # :nodoc:
         with_raw_connection do |conn|
-          conn.server_version
+          version = conn.server_version
+          if version == 0
+            raise ActiveRecord::ConnectionFailed, "Could not determine PostgreSQL version"
+          end
+          version
         end
       end
       alias :postgresql_version :database_version

activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb

@@ -95,6 +95,26 @@ def test_bad_connection_to_postgres_database
         end
       end
 
+      def test_reconnect_after_bad_connection_on_check_version
+        db_config = ActiveRecord::Base.configurations.configs_for(env_name: "arunit", name: "primary")
+        connection = ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.new(db_config.configuration_hash.merge(connection_retries: 0))
+        connection.connect!
+
+        # mimic a connection that hasn't checked and cached the server version yet i.e. without a raw_connection
+        connection.pool.instance_variable_set(:@server_version, nil)
+        connection.raw_connection.stub(:server_version, 0) do
+          error = assert_raises ActiveRecord::ConnectionFailed do
+            connection.reconnect!
+          end
+          assert_equal "Could not determine PostgreSQL version", error.message
+        end
+
+        # can reconnect after a bad connection
+        assert_nothing_raised do
+          connection.reconnect!
+        end
+      end
+
       def test_database_exists_returns_false_when_the_database_does_not_exist
         config = { database: "non_extant_database", adapter: "postgresql" }
         assert_not ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.database_exists?(config),