[SPARK-13625][PYSPARK][ML] Added a check to see if an attribute is a property...

[SPARK-13625][PYSPARK][ML] Added a check to see if an attribute is a property when getting param list

## What changes were proposed in this pull request?

Added a check in pyspark.ml.param.Param.params() to see if an attribute is a property (decorated with `property`) before checking if it is a `Param` instance.  This prevents the property from being invoked to 'get' this attribute, which could possibly cause an error.

## How was this patch tested?

Added a test case with a class has a property that will raise an error when invoked and then call`Param.params` to verify that the property is not invoked, but still able to find another property in the class.  Also ran pyspark-ml test before fix that will trigger an error, and again after the fix to verify that the error was resolved and the method was working properly.

Author: Bryan Cutler <cutlerb@gmail.com>

Closes #11476 from BryanCutler/pyspark-ml-property-attr-SPARK-13625.

python/pyspark/ml/param/__init__.py

@@ -109,7 +109,8 @@ class Params(Identifiable):
         """
         if self._params is None:
             self._params = list(filter(lambda attr: isinstance(attr, Param),
-                                       [getattr(self, x) for x in dir(self) if x != "params"]))
+                                       [getattr(self, x) for x in dir(self) if x != "params" and
+                                        not isinstance(getattr(type(self), x, None), property)]))
         return self._params
 
     @since("1.4.0")

python/pyspark/ml/tests.py

@@ -271,6 +271,12 @@ class ParamTests(PySparkTestCase):
         # Check that a different class has a different seed
         self.assertNotEqual(other.getSeed(), noSeedSpecd.getSeed())
 
+    def test_param_property_error(self):
+        param_store = HasThrowableProperty()
+        self.assertRaises(RuntimeError, lambda: param_store.test_property)
+        params = param_store.params  # should not invoke the property 'test_property'
+        self.assertEqual(len(params), 1)
+
 
 class FeatureTests(PySparkTestCase):
 
@@ -494,6 +500,17 @@ class PersistenceTest(PySparkTestCase):
             pass
 
 
+class HasThrowableProperty(Params):
+
+    def __init__(self):
+        super(HasThrowableProperty, self).__init__()
+        self.p = Param(self, "none", "empty param")
+
+    @property
+    def test_property(self):
+        raise RuntimeError("Test property to raise error when invoked")
+
+
 if __name__ == "__main__":
     from pyspark.ml.tests import *
     if xmlrunner: