Removed empty if, added disable unit test for python.

Author: TongruiLi

sdks/go/pkg/beam/runners/dataflow/dataflow.go

@@ -369,9 +369,7 @@ func getJobOptions(ctx context.Context, streaming bool) (*dataflowlib.JobOptions
 	if !portaSubmission {
 		experiments = append(experiments, "use_portable_job_submission")
 	}
-	if !portableRunnerSet {
-		// As this option is not documented, we do not set it by default. This behavior will be fixed in later versions.
-	}
+	// As portable_runner is not documented, we do not set it by default. This behavior will be fixed in later versions.
 
 	// Ensure that streaming specific experiments are set for streaming pipelines
 	// since runner v2 only supports using streaming engine.

sdks/python/apache_beam/runners/dataflow/dataflow_runner_test.py

@@ -41,6 +41,7 @@
 from apache_beam.runners.dataflow.dataflow_runner import DataflowRuntimeException
 from apache_beam.runners.dataflow.dataflow_runner import _check_and_add_missing_options
 from apache_beam.runners.dataflow.dataflow_runner import _check_and_add_missing_streaming_options
+from apache_beam.runners.dataflow.dataflow_runner import _is_runner_v2_disabled
 from apache_beam.runners.dataflow.internal.clients import dataflow as dataflow_api
 from apache_beam.runners.internal import names
 from apache_beam.runners.runner import PipelineState
@@ -734,5 +735,27 @@ def test_explicit_streaming_no_unbounded(self):
         apiclient.dataflow.Job.TypeValueValuesEnum.JOB_TYPE_STREAMING)
 
 
+class DataflowRunnerV2DisabledTest(unittest.TestCase):
+
+  def test_runner_v2_disabled_experiments_raise(self):
+    disable_experiments = [
+        'disable_portable_runner',
+        'enable_streaming_java_runner',
+        'disable_runner_v2',
+        'disable_runner_v2_until_2023',
+        'disable_runner_v2_until_v2.50',
+        'disable_prime_runner_v2',
+    ]
+    for experiment in disable_experiments:
+      options = PipelineOptions([f'--experiments={experiment}'])
+      self.assertTrue(
+          _is_runner_v2_disabled(options),
+          f'Expected {experiment} to disable runner v2')
+      with self.assertRaisesRegex(
+          ValueError,
+          'Disabling Runner V2 no longer supported'):
+        DataflowRunner().run_pipeline(None, options)
+
+
 if __name__ == '__main__':
   unittest.main()