Fix dotnet and job description methods / tests

python/gresearch/spark/__init__.py

@@ -47,6 +47,12 @@
 
 
 def _get_jvm(obj: Any) -> JVMView:
+    if obj is None:
+        if SparkContext._active_spark_context is None:
+            raise RuntimeError("This method must be called inside an active Spark session")
+        else:
+            raise ValueError("Cannot provide access to JVM from None")
+
     # helper method to assert the JVM is accessible and provide a useful error message
     if has_connect and isinstance(obj, (ConnectDataFrame, ConnectDataFrameReader, ConnectSparkSession)):
         raise RuntimeError('This feature is not supported for Spark Connect. Please use a classic Spark client. https://github.com/G-Research/spark-extension#spark-connect-server')

python/test/test_jvm.py

@@ -84,7 +84,7 @@ def test_dotnet_ticks(self):
             with self.subTest(label):
                 with self.assertRaises(RuntimeError) as e:
                     func("id")
-                self.assertEqual((EXPECTED_UNSUPPORTED_MESSAGE, ), e.exception.args)
+                self.assertEqual(("This method must be called inside an active Spark session", ), e.exception.args)
 
     @skipUnless(SparkTest.is_spark_connect, "Spark connect client tests")
     def test_histogram(self):
@@ -103,12 +103,12 @@ def test_job_description(self):
         with self.assertRaises(RuntimeError) as e:
             with job_description("job description"):
                 pass
-        self.assertEqual((EXPECTED_UNSUPPORTED_MESSAGE, ), e.exception.args)
+        self.assertEqual(("This method must be called inside an active Spark session", ), e.exception.args)
 
         with self.assertRaises(RuntimeError) as e:
             with append_description("job description"):
                 pass
-        self.assertEqual((EXPECTED_UNSUPPORTED_MESSAGE, ), e.exception.args)
+        self.assertEqual(("This method must be called inside an active Spark session", ), e.exception.args)
 
     @skipUnless(SparkTest.is_spark_connect, "Spark connect client tests")
     def test_create_temp_dir(self):