From 6082d305f0791d95032fee1f6e3d98775dd79479 Mon Sep 17 00:00:00 2001
From: Seth Hollyman <shollyman@google.com>
Date: Mon, 6 Apr 2020 20:38:07 +0000
Subject: [PATCH 01/19] feat: add support for policy tags in schema

---
 google/cloud/bigquery/schema.py | 100 +++++++++++++++++++++++++++++++-
 tests/unit/test_schema.py       |  28 +++++++--
 2 files changed, 122 insertions(+), 6 deletions(-)

diff --git a/google/cloud/bigquery/schema.py b/google/cloud/bigquery/schema.py
index 3878a80a9..13e861790 100644
--- a/google/cloud/bigquery/schema.py
+++ b/google/cloud/bigquery/schema.py
@@ -62,14 +62,19 @@ class SchemaField(object):
 
         fields (Tuple[google.cloud.bigquery.schema.SchemaField]):
             subfields (requires ``field_type`` of 'RECORD').
+
+        policy_tags (Optional[PolicyTagList]): The policy tag list for the field.
+
     """
 
-    def __init__(self, name, field_type, mode="NULLABLE", description=None, fields=()):
+    def __init__(self, name, field_type, mode="NULLABLE", description=None, fields=(), policy_tags=None):
         self._name = name
         self._field_type = field_type
         self._mode = mode
         self._description = description
         self._fields = tuple(fields)
+        self._policy_tags = policy_tags
+
 
     @classmethod
     def from_api_repr(cls, api_repr):
@@ -87,12 +92,16 @@ def from_api_repr(cls, api_repr):
         mode = api_repr.get("mode", "NULLABLE")
         description = api_repr.get("description")
         fields = api_repr.get("fields", ())
+        policy_tags = api_repr.get("policyTags")
+        if policy_tags is not None:
+            policy_tags = PolicyTagList.from_api_repr(policy_tags)
         return cls(
             field_type=api_repr["type"].upper(),
             fields=[cls.from_api_repr(f) for f in fields],
             mode=mode.upper(),
             description=description,
             name=api_repr["name"],
+            policy_tags=policy_tags,
         )
 
     @property
@@ -136,6 +145,18 @@ def fields(self):
         """
         return self._fields
 
+    @property
+    def policy_tags(self):
+        """Optional[google.cloud.bigquery.schema.PolicyTagList]: Policy tag list
+        definition for this field.
+
+        Raises:
+            ValueError:
+                if the value is not :class:`~google.cloud.bigquery.schema.PolicyTagList`
+                or :data:`None`.
+        """
+        return self._policy_tags
+
     def to_api_repr(self):
         """Return a dictionary representing this schema field.
 
@@ -155,6 +176,10 @@ def to_api_repr(self):
         if self.field_type.upper() in _STRUCT_TYPES:
             answer["fields"] = [f.to_api_repr() for f in self.fields]
 
+        # If this contains a policy tag definition, include that as well:
+        if self.policy_tags is not None:
+            answer["policyTags"] = self.policy_tags.to_api_repr()
+
         # Done; return the serialized dictionary.
         return answer
 
@@ -172,6 +197,7 @@ def _key(self):
             self._mode.upper(),
             self._description,
             self._fields,
+            self._policy_tags,
         )
 
     def to_standard_sql(self):
@@ -244,7 +270,8 @@ def _parse_schema_resource(info):
         mode = r_field.get("mode", "NULLABLE")
         description = r_field.get("description")
         sub_fields = _parse_schema_resource(r_field)
-        schema.append(SchemaField(name, field_type, mode, description, sub_fields))
+        policy_tags = r_field.get("policyTags", None)
+        schema.append(SchemaField(name, field_type, mode, description, sub_fields, policy_tags))
     return schema
 
 
@@ -291,3 +318,72 @@ def _to_schema_fields(schema):
         field if isinstance(field, SchemaField) else SchemaField.from_api_repr(field)
         for field in schema
     ]
+
+class PolicyTagList(object):
+    """Define Policy Tags for a column.
+
+    Args:
+        names (Union[List[str], None]): list of policy tags to associate with
+            the column.
+    """
+
+    def __init__(self, names=None):
+        self._properties = {}
+        if names is not None:
+            self.names = names
+
+    @property
+    def names(self):
+        """Union[List[str], None]: Policy tags associated with this definition.
+        """
+        return self._properties.get("names", ())
+
+    @names.setter
+    def names(self, value):
+        """Union[List[str], None]: Policy tags associated with this definition.
+
+        (Defaults to :data:`None`).
+        """
+        if value is not None:
+            self._properties["names"] = value
+        else:
+            if "names" in self._properties:
+                del self._properties["names"]
+
+    @classmethod
+    def from_api_repr(cls, api_repr):
+        """Return a :class:`PolicyTagList` object deserialized from a dict.
+
+        This method creates a new ``PolicyTagList`` instance that points to
+        the ``api_repr`` parameter as its internal properties dict. This means
+        that when a ``PolicyTagList`` instance is stored as a property of
+        another object, any changes made at the higher level will also appear
+        here.
+
+        Args:
+            api_repr (Mapping[str, str]):
+                The serialized representation of the PolicyTagList, such as
+                what is output by :meth:`to_api_repr`.
+
+        Returns:
+            google.cloud.bigquery.schema.PolicyTagList:
+                The ``PolicyTagList`` object.
+        """
+        instance = cls()
+        instance._properties = api_repr
+        return instance
+
+    def to_api_repr(self):
+        """Return a dictionary representing this object.
+
+        This method returns the properties dict of the ``PolicyTagList``
+        instance rather than making a copy. This means that when a
+        ``PolicyTagList`` instance is stored as a property of another
+        object, any changes made at the higher level will also appear here.
+
+        Returns:
+            dict:
+                A dictionary representing the PolicyTagList object in
+                serialized form.
+        """
+        return self._properties
\ No newline at end of file
diff --git a/tests/unit/test_schema.py b/tests/unit/test_schema.py
index e1bdd7b2f..fb77341e9 100644
--- a/tests/unit/test_schema.py
+++ b/tests/unit/test_schema.py
@@ -63,13 +63,33 @@ def test_constructor_subfields(self):
         self.assertIs(field._fields[0], sub_field1)
         self.assertIs(field._fields[1], sub_field2)
 
+    def test_constructor_with_policy_tags(self):
+        from google.cloud.bigquery.schema import PolicyTagList
+        
+        policy = PolicyTagList(names=("foo", "bar"))
+        field = self._make_one("test", "STRING", mode="REQUIRED", description="Testing", policy_tags=policy)
+        self.assertEqual(field._name, "test")
+        self.assertEqual(field._field_type, "STRING")
+        self.assertEqual(field._mode, "REQUIRED")
+        self.assertEqual(field._description, "Testing")
+        self.assertEqual(field._fields, ())
+        self.assertEqual(field._policy_tags, policy)
+
     def test_to_api_repr(self):
-        field = self._make_one("foo", "INTEGER", "NULLABLE")
+        from google.cloud.bigquery.schema import PolicyTagList
+        
+        policy = PolicyTagList(names=("foo", "bar"))
         self.assertEqual(
-            field.to_api_repr(),
-            {"mode": "NULLABLE", "name": "foo", "type": "INTEGER", "description": None},
+            policy.to_api_repr(),
+            {"names": ("foo", "bar")} ,
         )
 
+        field = self._make_one("foo", "INTEGER", "NULLABLE", policy_tags=policy)
+        self.assertEqual(
+            field.to_api_repr(),
+            {"mode": "NULLABLE", "name": "foo", "type": "INTEGER", "description": None, "policyTags": {"names": ("foo","bar")}},
+        )
+        
     def test_to_api_repr_with_subfield(self):
         for record_type in ("RECORD", "STRUCT"):
             subfield = self._make_one("bar", "INTEGER", "NULLABLE")
@@ -408,7 +428,7 @@ def test___hash__not_equals(self):
 
     def test___repr__(self):
         field1 = self._make_one("field1", "STRING")
-        expected = "SchemaField('field1', 'STRING', 'NULLABLE', None, ())"
+        expected = "SchemaField('field1', 'STRING', 'NULLABLE', None, (), None)"
         self.assertEqual(repr(field1), expected)
 
 

From 88790b5d51251d9e4b2748c1524a7d302c4ec37f Mon Sep 17 00:00:00 2001
From: Seth Hollyman <shollyman@google.com>
Date: Thu, 16 Apr 2020 18:23:52 +0000
Subject: [PATCH 02/19] blacken

---
 google/cloud/bigquery/schema.py | 18 ++++++++++++++----
 tests/unit/test_schema.py       | 21 ++++++++++++++-------
 2 files changed, 28 insertions(+), 11 deletions(-)

diff --git a/google/cloud/bigquery/schema.py b/google/cloud/bigquery/schema.py
index 13e861790..71271a4c2 100644
--- a/google/cloud/bigquery/schema.py
+++ b/google/cloud/bigquery/schema.py
@@ -67,7 +67,15 @@ class SchemaField(object):
 
     """
 
-    def __init__(self, name, field_type, mode="NULLABLE", description=None, fields=(), policy_tags=None):
+    def __init__(
+        self,
+        name,
+        field_type,
+        mode="NULLABLE",
+        description=None,
+        fields=(),
+        policy_tags=None,
+    ):
         self._name = name
         self._field_type = field_type
         self._mode = mode
@@ -75,7 +83,6 @@ def __init__(self, name, field_type, mode="NULLABLE", description=None, fields=(
         self._fields = tuple(fields)
         self._policy_tags = policy_tags
 
-
     @classmethod
     def from_api_repr(cls, api_repr):
         """Return a ``SchemaField`` object deserialized from a dictionary.
@@ -271,7 +278,9 @@ def _parse_schema_resource(info):
         description = r_field.get("description")
         sub_fields = _parse_schema_resource(r_field)
         policy_tags = r_field.get("policyTags", None)
-        schema.append(SchemaField(name, field_type, mode, description, sub_fields, policy_tags))
+        schema.append(
+            SchemaField(name, field_type, mode, description, sub_fields, policy_tags)
+        )
     return schema
 
 
@@ -319,6 +328,7 @@ def _to_schema_fields(schema):
         for field in schema
     ]
 
+
 class PolicyTagList(object):
     """Define Policy Tags for a column.
 
@@ -386,4 +396,4 @@ def to_api_repr(self):
                 A dictionary representing the PolicyTagList object in
                 serialized form.
         """
-        return self._properties
\ No newline at end of file
+        return self._properties
diff --git a/tests/unit/test_schema.py b/tests/unit/test_schema.py
index fb77341e9..d09abf263 100644
--- a/tests/unit/test_schema.py
+++ b/tests/unit/test_schema.py
@@ -65,9 +65,11 @@ def test_constructor_subfields(self):
 
     def test_constructor_with_policy_tags(self):
         from google.cloud.bigquery.schema import PolicyTagList
-        
+
         policy = PolicyTagList(names=("foo", "bar"))
-        field = self._make_one("test", "STRING", mode="REQUIRED", description="Testing", policy_tags=policy)
+        field = self._make_one(
+            "test", "STRING", mode="REQUIRED", description="Testing", policy_tags=policy
+        )
         self.assertEqual(field._name, "test")
         self.assertEqual(field._field_type, "STRING")
         self.assertEqual(field._mode, "REQUIRED")
@@ -77,19 +79,24 @@ def test_constructor_with_policy_tags(self):
 
     def test_to_api_repr(self):
         from google.cloud.bigquery.schema import PolicyTagList
-        
+
         policy = PolicyTagList(names=("foo", "bar"))
         self.assertEqual(
-            policy.to_api_repr(),
-            {"names": ("foo", "bar")} ,
+            policy.to_api_repr(), {"names": ("foo", "bar")},
         )
 
         field = self._make_one("foo", "INTEGER", "NULLABLE", policy_tags=policy)
         self.assertEqual(
             field.to_api_repr(),
-            {"mode": "NULLABLE", "name": "foo", "type": "INTEGER", "description": None, "policyTags": {"names": ("foo","bar")}},
+            {
+                "mode": "NULLABLE",
+                "name": "foo",
+                "type": "INTEGER",
+                "description": None,
+                "policyTags": {"names": ("foo", "bar")},
+            },
         )
-        
+
     def test_to_api_repr_with_subfield(self):
         for record_type in ("RECORD", "STRUCT"):
             subfield = self._make_one("bar", "INTEGER", "NULLABLE")

From d756cf2d1276b41c7da46b3744e4da8bc5579f22 Mon Sep 17 00:00:00 2001
From: Seth Hollyman <shollyman@google.com>
Date: Thu, 16 Apr 2020 20:37:17 +0000
Subject: [PATCH 03/19] add more unit coverage

---
 tests/unit/test_schema.py | 42 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/tests/unit/test_schema.py b/tests/unit/test_schema.py
index d09abf263..e0efa37fb 100644
--- a/tests/unit/test_schema.py
+++ b/tests/unit/test_schema.py
@@ -138,6 +138,24 @@ def test_from_api_repr(self):
         self.assertEqual(field.fields[0].field_type, "INTEGER")
         self.assertEqual(field.fields[0].mode, "NULLABLE")
 
+    def test_from_api_repr_policy(self):
+        field = self._get_target_class().from_api_repr(
+            {
+                "fields": [{"mode": "nullable", "name": "bar", "type": "integer"}],
+                "name": "foo",
+                "type": "record",
+                "policyTags": ("one", "two"),
+            }
+        )
+        self.assertEqual(field.name, "foo")
+        self.assertEqual(field.field_type, "RECORD")
+        self.assertEqual(field.description, "test_description")
+        self.assertEqual(len(field.fields), 1)
+        self.assertEqual(field.fields[0].name, "bar")
+        self.assertEqual(field.fields[0].field_type, "INTEGER")
+        self.assertEqual(field.fields[0].mode, "NULLABLE")
+        self.assertEqual(field.policy_tags, ("one", "two"))
+
     def test_from_api_repr_defaults(self):
         field = self._get_target_class().from_api_repr(
             {"name": "foo", "type": "record"}
@@ -659,3 +677,27 @@ def test_valid_mapping_representation(self):
 
         result = self._call_fut(schema)
         self.assertEqual(result, expected_schema)
+
+
+class TestPolicyTags(unittest.TestCase):
+    @staticmethod
+    def _get_target_class():
+        from google.cloud.bigquery.schema import PolicyTagList
+
+        return PolicyTagList
+
+    def _make_one(self, *args, **kw):
+        return self._get_target_class()(*args, **kw)
+
+    def test_constructor(self):
+        empty_policy_tags = self._make_one()
+        self.assertIsNotNone(empty_policy_tags.names)
+        self.assertEqual(len(empty_policy_tags.names), 0)
+        policy_tags = self._make_one(("foo", "bar"))
+        self.assertEqual(policy_tags.names, ("foo", "bar"))
+
+    def test_from_api_repr(self):
+        klass = self._get_target_class()
+        api_repr = {"names": ("foo")}
+        policy_tags = klass.from_api_repr(api_repr)
+        self.assertEqual(policy_tags.to_api_repr(), api_repr)

From ae04022ebe18daa1e8fd660993188ea66884fd30 Mon Sep 17 00:00:00 2001
From: Seth Hollyman <shollyman@google.com>
Date: Thu, 16 Apr 2020 21:21:12 +0000
Subject: [PATCH 04/19] more test cleanup

---
 tests/unit/test_schema.py | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/tests/unit/test_schema.py b/tests/unit/test_schema.py
index e0efa37fb..093167514 100644
--- a/tests/unit/test_schema.py
+++ b/tests/unit/test_schema.py
@@ -144,17 +144,16 @@ def test_from_api_repr_policy(self):
                 "fields": [{"mode": "nullable", "name": "bar", "type": "integer"}],
                 "name": "foo",
                 "type": "record",
-                "policyTags": ("one", "two"),
+                "policyTags": {"names": ("one", "two")},
             }
         )
         self.assertEqual(field.name, "foo")
         self.assertEqual(field.field_type, "RECORD")
-        self.assertEqual(field.description, "test_description")
+        self.assertEqual(field.policy_tags.names, ("one", "two"))
         self.assertEqual(len(field.fields), 1)
         self.assertEqual(field.fields[0].name, "bar")
         self.assertEqual(field.fields[0].field_type, "INTEGER")
         self.assertEqual(field.fields[0].mode, "NULLABLE")
-        self.assertEqual(field.policy_tags, ("one", "two"))
 
     def test_from_api_repr_defaults(self):
         field = self._get_target_class().from_api_repr(

From ab27d788ddc7eefb189356d04d3595ae8e7e061e Mon Sep 17 00:00:00 2001
From: Seth Hollyman <shollyman@google.com>
Date: Thu, 16 Apr 2020 23:55:04 +0000
Subject: [PATCH 05/19] more tests

---
 google/cloud/bigquery/schema.py | 1 +
 tests/unit/test_schema.py       | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/google/cloud/bigquery/schema.py b/google/cloud/bigquery/schema.py
index 71271a4c2..ef773bda1 100644
--- a/google/cloud/bigquery/schema.py
+++ b/google/cloud/bigquery/schema.py
@@ -355,6 +355,7 @@ def names(self, value):
         (Defaults to :data:`None`).
         """
         if value is not None:
+            prop = self._properties.setdefault("names", ())
             self._properties["names"] = value
         else:
             if "names" in self._properties:
diff --git a/tests/unit/test_schema.py b/tests/unit/test_schema.py
index 093167514..db61cf627 100644
--- a/tests/unit/test_schema.py
+++ b/tests/unit/test_schema.py
@@ -700,3 +700,11 @@ def test_from_api_repr(self):
         api_repr = {"names": ("foo")}
         policy_tags = klass.from_api_repr(api_repr)
         self.assertEqual(policy_tags.to_api_repr(), api_repr)
+
+    def test_setter(self):
+        policy_tags = self._make_one()
+        self.assertEqual(len(policy_tags.names), 0)
+        policy_tags.names = ("foo", "bar")
+        self.assertEqual(policy_tags.names, ("foo", "bar"))
+        policy_tags.names = None
+        self.assertEqual(policy_tags.names, ())

From dc7170c667872a4a26cdd0105a73015f24659a7a Mon Sep 17 00:00:00 2001
From: Seth Hollyman <shollyman@google.com>
Date: Fri, 17 Apr 2020 05:17:18 +0000
Subject: [PATCH 06/19] formatting

---
 google/cloud/bigquery/schema.py | 1 -
 tests/unit/test_schema.py       | 6 ++++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/google/cloud/bigquery/schema.py b/google/cloud/bigquery/schema.py
index ef773bda1..71271a4c2 100644
--- a/google/cloud/bigquery/schema.py
+++ b/google/cloud/bigquery/schema.py
@@ -355,7 +355,6 @@ def names(self, value):
         (Defaults to :data:`None`).
         """
         if value is not None:
-            prop = self._properties.setdefault("names", ())
             self._properties["names"] = value
         else:
             if "names" in self._properties:
diff --git a/tests/unit/test_schema.py b/tests/unit/test_schema.py
index db61cf627..d5bc5f369 100644
--- a/tests/unit/test_schema.py
+++ b/tests/unit/test_schema.py
@@ -701,6 +701,12 @@ def test_from_api_repr(self):
         policy_tags = klass.from_api_repr(api_repr)
         self.assertEqual(policy_tags.to_api_repr(), api_repr)
 
+    def test_to_api_repr(self):
+        taglist = self._make_one(names=("foo", "bar"))
+        self.assertEqual(
+            taglist.to_api_repr(), {"names": ("foo", "bar")},
+        )
+
     def test_setter(self):
         policy_tags = self._make_one()
         self.assertEqual(len(policy_tags.names), 0)

From c06d4a655a944dd174b23f1701b79fd8d4b0abe3 Mon Sep 17 00:00:00 2001
From: Seth Hollyman <shollyman@google.com>
Date: Fri, 17 Apr 2020 18:32:08 +0000
Subject: [PATCH 07/19] more testing of names setter

---
 tests/unit/test_schema.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tests/unit/test_schema.py b/tests/unit/test_schema.py
index d5bc5f369..ebad2621a 100644
--- a/tests/unit/test_schema.py
+++ b/tests/unit/test_schema.py
@@ -709,7 +709,9 @@ def test_to_api_repr(self):
 
     def test_setter(self):
         policy_tags = self._make_one()
-        self.assertEqual(len(policy_tags.names), 0)
+        self.assertEqual(policy_tags.names, ())
+        policy_tags.names = None
+        self.assertEqual(policy_tags.names, ())
         policy_tags.names = ("foo", "bar")
         self.assertEqual(policy_tags.names, ("foo", "bar"))
         policy_tags.names = None

From 3bd1e7fcee0063490006752e47e409741e88752d Mon Sep 17 00:00:00 2001
From: Seth Hollyman <shollyman@google.com>
Date: Mon, 20 Apr 2020 20:54:55 +0000
Subject: [PATCH 08/19] address reviewer comments

---
 google/cloud/bigquery/schema.py | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/google/cloud/bigquery/schema.py b/google/cloud/bigquery/schema.py
index 71271a4c2..50cd9fa7e 100644
--- a/google/cloud/bigquery/schema.py
+++ b/google/cloud/bigquery/schema.py
@@ -14,6 +14,8 @@
 
 """Schemas for BigQuery tables / queries."""
 
+import copy
+
 from six.moves import collections_abc
 
 from google.cloud.bigquery_v2 import types
@@ -159,7 +161,7 @@ def policy_tags(self):
 
         Raises:
             ValueError:
-                if the value is not :class:`~google.cloud.bigquery.schema.PolicyTagList`
+                If the value is not :class:`~google.cloud.bigquery.schema.PolicyTagList`
                 or :data:`None`.
         """
         return self._policy_tags
@@ -277,7 +279,7 @@ def _parse_schema_resource(info):
         mode = r_field.get("mode", "NULLABLE")
         description = r_field.get("description")
         sub_fields = _parse_schema_resource(r_field)
-        policy_tags = r_field.get("policyTags", None)
+        policy_tags = r_field.get("policyTags")
         schema.append(
             SchemaField(name, field_type, mode, description, sub_fields, policy_tags)
         )
@@ -333,24 +335,23 @@ class PolicyTagList(object):
     """Define Policy Tags for a column.
 
     Args:
-        names (Union[List[str], None]): list of policy tags to associate with
+        names (Union[Tuple[str], None]): list of policy tags to associate with
             the column.
     """
 
     def __init__(self, names=None):
         self._properties = {}
-        if names is not None:
-            self.names = names
+        self.names = names
 
     @property
     def names(self):
-        """Union[List[str], None]: Policy tags associated with this definition.
+        """Tuple[str]: Policy tags associated with this definition.
         """
         return self._properties.get("names", ())
 
     @names.setter
     def names(self, value):
-        """Union[List[str], None]: Policy tags associated with this definition.
+        """Union[Tuple[str], None]: Policy tags associated with this definition.
 
         (Defaults to :data:`None`).
         """
@@ -380,7 +381,7 @@ def from_api_repr(cls, api_repr):
                 The ``PolicyTagList`` object.
         """
         instance = cls()
-        instance._properties = api_repr
+        instance._properties = copy.deepcopy(api_repr)
         return instance
 
     def to_api_repr(self):

From b71b87195f0cf9f36645b3e67baa0ba26333f706 Mon Sep 17 00:00:00 2001
From: Seth Hollyman <shollyman@google.com>
Date: Mon, 20 Apr 2020 20:57:21 +0000
Subject: [PATCH 09/19] docstrings migrate from unions -> optional

---
 google/cloud/bigquery/schema.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/google/cloud/bigquery/schema.py b/google/cloud/bigquery/schema.py
index 50cd9fa7e..4377160b1 100644
--- a/google/cloud/bigquery/schema.py
+++ b/google/cloud/bigquery/schema.py
@@ -335,7 +335,7 @@ class PolicyTagList(object):
     """Define Policy Tags for a column.
 
     Args:
-        names (Union[Tuple[str], None]): list of policy tags to associate with
+        names (Optional[Tuple[str]]): list of policy tags to associate with
             the column.
     """
 
@@ -351,7 +351,7 @@ def names(self):
 
     @names.setter
     def names(self, value):
-        """Union[Tuple[str], None]: Policy tags associated with this definition.
+        """Optional[Tuple[str]]: Policy tags associated with this definition.
 
         (Defaults to :data:`None`).
         """

From 1d704c56820537ed72b6976e18099963b361516c Mon Sep 17 00:00:00 2001
From: Seth Hollyman <shollyman@google.com>
Date: Thu, 30 Apr 2020 19:23:11 +0000
Subject: [PATCH 10/19] stashing changes

---
 google/cloud/bigquery/schema.py | 22 ++++++++++----
 tests/system.py                 | 51 +++++++++++++++++++++++++++++++++
 2 files changed, 67 insertions(+), 6 deletions(-)

diff --git a/google/cloud/bigquery/schema.py b/google/cloud/bigquery/schema.py
index 4377160b1..90c75e835 100644
--- a/google/cloud/bigquery/schema.py
+++ b/google/cloud/bigquery/schema.py
@@ -101,16 +101,14 @@ def from_api_repr(cls, api_repr):
         mode = api_repr.get("mode", "NULLABLE")
         description = api_repr.get("description")
         fields = api_repr.get("fields", ())
-        policy_tags = api_repr.get("policyTags")
-        if policy_tags is not None:
-            policy_tags = PolicyTagList.from_api_repr(policy_tags)
+
         return cls(
             field_type=api_repr["type"].upper(),
             fields=[cls.from_api_repr(f) for f in fields],
             mode=mode.upper(),
             description=description,
             name=api_repr["name"],
-            policy_tags=policy_tags,
+            policy_tags=PolicyTagList.from_api_repr(api_repr.get("policyTags")),
         )
 
     @property
@@ -279,7 +277,7 @@ def _parse_schema_resource(info):
         mode = r_field.get("mode", "NULLABLE")
         description = r_field.get("description")
         sub_fields = _parse_schema_resource(r_field)
-        policy_tags = r_field.get("policyTags")
+        policy_tags = PolicyTagList.from_api_repr(r_field.get("policyTags"))
         schema.append(
             SchemaField(name, field_type, mode, description, sub_fields, policy_tags)
         )
@@ -356,11 +354,20 @@ def names(self, value):
         (Defaults to :data:`None`).
         """
         if value is not None:
-            self._properties["names"] = value
+            self._properties["names"] = tuple(value)
         else:
             if "names" in self._properties:
                 del self._properties["names"]
 
+    def __eq__(self, other):
+        if isinstance(other, self.__class__):
+            return self.__dict__ == other.__dict__
+        else:
+            return False
+
+    def __ne__(self, other):
+        return not self.__eq__(other)
+
     @classmethod
     def from_api_repr(cls, api_repr):
         """Return a :class:`PolicyTagList` object deserialized from a dict.
@@ -382,6 +389,9 @@ def from_api_repr(cls, api_repr):
         """
         instance = cls()
         instance._properties = copy.deepcopy(api_repr)
+        # ensure the representation is immutable
+        if instance._properties is not None:
+            instance.names = instance.names
         return instance
 
     def to_api_repr(self):
diff --git a/tests/system.py b/tests/system.py
index 98a1edaa5..7744fdfdd 100644
--- a/tests/system.py
+++ b/tests/system.py
@@ -335,6 +335,57 @@ def test_create_table(self):
         self.assertTrue(_table_exists(table))
         self.assertEqual(table.table_id, table_id)
 
+    def test_create_table_with_policy(self):
+        from google.cloud.bigquery.schema import PolicyTagList
+
+        dataset = self.temp_dataset(_make_dataset_id("create_table_with_policy"))
+        table_id = "test_table"
+        policy_1 = PolicyTagList(
+            names=(
+                "projects/{}/locations/us/taxonomies/1/policyTags/2".format(
+                    Config.CLIENT.project
+                ),
+            )
+        )
+        policy_2 = PolicyTagList(
+            names=(
+                "projects/{}/locations/us/taxonomies/3/policyTags/4".format(
+                    Config.CLIENT.project
+                ),
+            )
+        )
+
+        schema = [
+            bigquery.SchemaField("full_name", "STRING", mode="REQUIRED"),
+            bigquery.SchemaField(
+                "secret_int", "INTEGER", mode="REQUIRED", policy_tags=policy_1
+            ),
+        ]
+        table_arg = Table(dataset.table(table_id), schema=schema)
+        self.assertFalse(_table_exists(table_arg))
+
+        table = retry_403(Config.CLIENT.create_table)(table_arg)
+        self.to_delete.insert(0, table)
+
+        self.assertTrue(_table_exists(table))
+        self.assertEqual(policy_1, table.schema[1].policy_tags)
+
+        # Amend the schema to replace the policy tags
+        new_schema = table.schema[:]
+        old_field = table.schema[1]
+        new_schema[1] = bigquery.SchemaField(
+            name=old_field.name,
+            field_type=old_field.field_type,
+            mode=old_field.mode,
+            description=old_field.description,
+            fields=old_field.fields,
+            policy_tags=policy_2,
+        )
+
+        table.schema = new_schema
+        table2 = Config.CLIENT.update_table(table, ["schema",])
+        self.assertEqual(policy_2, table.schema[1].policy_tags)
+
     def test_create_table_w_time_partitioning_w_clustering_fields(self):
         from google.cloud.bigquery.table import TimePartitioning
         from google.cloud.bigquery.table import TimePartitioningType

From 9cebe40e72e666da5c7465baa9e86b5140befbe1 Mon Sep 17 00:00:00 2001
From: Seth Hollyman <shollyman@google.com>
Date: Thu, 14 May 2020 19:09:27 +0000
Subject: [PATCH 11/19] revision to list-based representation, update tests

---
 google/cloud/bigquery/schema.py | 18 +++++++++---------
 tests/system.py                 |  4 ++--
 tests/unit/test_schema.py       | 14 +++++++-------
 3 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/google/cloud/bigquery/schema.py b/google/cloud/bigquery/schema.py
index 90c75e835..02154e5c8 100644
--- a/google/cloud/bigquery/schema.py
+++ b/google/cloud/bigquery/schema.py
@@ -333,8 +333,9 @@ class PolicyTagList(object):
     """Define Policy Tags for a column.
 
     Args:
-        names (Optional[Tuple[str]]): list of policy tags to associate with
-            the column.
+        names (Optional[List[str]]): list of policy tags to associate with
+            the column.  Policy tag identifiers are of the form
+            `projects/*/locations/*/taxonomies/*/policyTags/*`.
     """
 
     def __init__(self, names=None):
@@ -343,18 +344,18 @@ def __init__(self, names=None):
 
     @property
     def names(self):
-        """Tuple[str]: Policy tags associated with this definition.
+        """List[str]: Policy tags associated with this definition.
         """
-        return self._properties.get("names", ())
+        return self._properties.get("names", [])
 
     @names.setter
     def names(self, value):
-        """Optional[Tuple[str]]: Policy tags associated with this definition.
+        """Optional[List[str]]: Policy tags associated with this definition.
 
         (Defaults to :data:`None`).
         """
         if value is not None:
-            self._properties["names"] = tuple(value)
+            self._properties["names"] = value
         else:
             if "names" in self._properties:
                 del self._properties["names"]
@@ -387,11 +388,10 @@ def from_api_repr(cls, api_repr):
             google.cloud.bigquery.schema.PolicyTagList:
                 The ``PolicyTagList`` object.
         """
+        if api_repr is None:
+            return None
         instance = cls()
         instance._properties = copy.deepcopy(api_repr)
-        # ensure the representation is immutable
-        if instance._properties is not None:
-            instance.names = instance.names
         return instance
 
     def to_api_repr(self):
diff --git a/tests/system.py b/tests/system.py
index 7744fdfdd..c0a11e380 100644
--- a/tests/system.py
+++ b/tests/system.py
@@ -341,11 +341,11 @@ def test_create_table_with_policy(self):
         dataset = self.temp_dataset(_make_dataset_id("create_table_with_policy"))
         table_id = "test_table"
         policy_1 = PolicyTagList(
-            names=(
+            names=[
                 "projects/{}/locations/us/taxonomies/1/policyTags/2".format(
                     Config.CLIENT.project
                 ),
-            )
+            ]
         )
         policy_2 = PolicyTagList(
             names=(
diff --git a/tests/unit/test_schema.py b/tests/unit/test_schema.py
index ebad2621a..e2b59bb16 100644
--- a/tests/unit/test_schema.py
+++ b/tests/unit/test_schema.py
@@ -144,12 +144,12 @@ def test_from_api_repr_policy(self):
                 "fields": [{"mode": "nullable", "name": "bar", "type": "integer"}],
                 "name": "foo",
                 "type": "record",
-                "policyTags": {"names": ("one", "two")},
+                "policyTags": {"names": ["one", "two"]},
             }
         )
         self.assertEqual(field.name, "foo")
         self.assertEqual(field.field_type, "RECORD")
-        self.assertEqual(field.policy_tags.names, ("one", "two"))
+        self.assertEqual(field.policy_tags.names, ["one", "two"])
         self.assertEqual(len(field.fields), 1)
         self.assertEqual(field.fields[0].name, "bar")
         self.assertEqual(field.fields[0].field_type, "INTEGER")
@@ -709,10 +709,10 @@ def test_to_api_repr(self):
 
     def test_setter(self):
         policy_tags = self._make_one()
-        self.assertEqual(policy_tags.names, ())
+        self.assertEqual(policy_tags.names, [])
         policy_tags.names = None
-        self.assertEqual(policy_tags.names, ())
-        policy_tags.names = ("foo", "bar")
-        self.assertEqual(policy_tags.names, ("foo", "bar"))
+        self.assertEqual(policy_tags.names, [])
+        policy_tags.names = ["foo", "bar"]
+        self.assertEqual(policy_tags.names, ["foo", "bar"])
         policy_tags.names = None
-        self.assertEqual(policy_tags.names, ())
+        self.assertEqual(policy_tags.names, [])

From 51722a54e4b9452f553dcd7497c6a98578a8bf28 Mon Sep 17 00:00:00 2001
From: Seth Hollyman <shollyman@google.com>
Date: Thu, 14 May 2020 23:05:44 +0000
Subject: [PATCH 12/19] changes to equality and testing, towards satisfying
 coverage

---
 google/cloud/bigquery/schema.py | 25 ++++++++++++++++++++-----
 tests/system.py                 |  8 ++++----
 tests/unit/test_schema.py       | 21 ++++++++++++++++-----
 3 files changed, 40 insertions(+), 14 deletions(-)

diff --git a/google/cloud/bigquery/schema.py b/google/cloud/bigquery/schema.py
index 02154e5c8..3f0c41241 100644
--- a/google/cloud/bigquery/schema.py
+++ b/google/cloud/bigquery/schema.py
@@ -360,14 +360,29 @@ def names(self, value):
             if "names" in self._properties:
                 del self._properties["names"]
 
+    def _key(self): 
+        """A tuple key that uniquely describes this PolicyTagList.
+
+        Used to compute this instance's hashcode and evaluate equality.
+
+        Returns:
+            Tuple: The contents of this :class:`~google.cloud.bigquery.schema.PolicyTagList`.
+        """
+        return tuple(sorted(self._properties.items()))
+
     def __eq__(self, other):
-        if isinstance(other, self.__class__):
-            return self.__dict__ == other.__dict__
-        else:
-            return False
+        if not isinstance(other, PolicyTagList):
+            return NotImplemented
+        return self._key() == other._key()
 
     def __ne__(self, other):
-        return not self.__eq__(other)
+        return not self == other
+
+    def __hash__(self):
+        return hash(self._key())
+
+    def __repr__(self):
+        return "PolicyTagList{}".format(self._key())
 
     @classmethod
     def from_api_repr(cls, api_repr):
diff --git a/tests/system.py b/tests/system.py
index 564cd082e..dfc9d65fe 100644
--- a/tests/system.py
+++ b/tests/system.py
@@ -352,11 +352,11 @@ def test_create_table_with_policy(self):
             ]
         )
         policy_2 = PolicyTagList(
-            names=(
+            names=[
                 "projects/{}/locations/us/taxonomies/3/policyTags/4".format(
                     Config.CLIENT.project
                 ),
-            )
+            ]
         )
 
         schema = [
@@ -387,8 +387,8 @@ def test_create_table_with_policy(self):
         )
 
         table.schema = new_schema
-        table2 = Config.CLIENT.update_table(table, ["schema",])
-        self.assertEqual(policy_2, table.schema[1].policy_tags)
+        table2 = Config.CLIENT.update_table(table, ["schema", ])
+        self.assertEqual(policy_2, table2.schema[1].policy_tags)
 
     def test_create_table_w_time_partitioning_w_clustering_fields(self):
         from google.cloud.bigquery.table import TimePartitioning
diff --git a/tests/unit/test_schema.py b/tests/unit/test_schema.py
index e2b59bb16..f0e606b55 100644
--- a/tests/unit/test_schema.py
+++ b/tests/unit/test_schema.py
@@ -692,19 +692,19 @@ def test_constructor(self):
         empty_policy_tags = self._make_one()
         self.assertIsNotNone(empty_policy_tags.names)
         self.assertEqual(len(empty_policy_tags.names), 0)
-        policy_tags = self._make_one(("foo", "bar"))
-        self.assertEqual(policy_tags.names, ("foo", "bar"))
+        policy_tags = self._make_one(["foo", "bar"])
+        self.assertEqual(policy_tags.names, ["foo", "bar"])
 
     def test_from_api_repr(self):
         klass = self._get_target_class()
-        api_repr = {"names": ("foo")}
+        api_repr = {"names": ["foo"]}
         policy_tags = klass.from_api_repr(api_repr)
         self.assertEqual(policy_tags.to_api_repr(), api_repr)
 
     def test_to_api_repr(self):
-        taglist = self._make_one(names=("foo", "bar"))
+        taglist = self._make_one(names=["foo", "bar"])
         self.assertEqual(
-            taglist.to_api_repr(), {"names": ("foo", "bar")},
+            taglist.to_api_repr(), {"names": ["foo", "bar"]},
         )
 
     def test_setter(self):
@@ -716,3 +716,14 @@ def test_setter(self):
         self.assertEqual(policy_tags.names, ["foo", "bar"])
         policy_tags.names = None
         self.assertEqual(policy_tags.names, [])
+
+    def test___eq___wrong_type(self):
+        policy = self._make_one(names=["foo", ])
+        other = object()
+        self.assertNotEqual(policy, other)
+        self.assertEqual(policy, mock.ANY)
+
+    def test___eq___names_mismatch(self):
+        policy = self._make_one(names=["foo", "bar"])
+        other = self._make_one(names=["bar", "baz"])
+        self.assertNotEqual(policy, other)
\ No newline at end of file

From c55fc7b2ba7d3304f6fe4822d8e5075cdee86a9a Mon Sep 17 00:00:00 2001
From: Seth Hollyman <shollyman@google.com>
Date: Fri, 15 May 2020 00:25:49 +0000
Subject: [PATCH 13/19] cleanup

---
 google/cloud/bigquery/schema.py | 5 +----
 tests/system.py                 | 2 +-
 tests/unit/test_schema.py       | 4 ++--
 3 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/google/cloud/bigquery/schema.py b/google/cloud/bigquery/schema.py
index 3f0c41241..0ec65c580 100644
--- a/google/cloud/bigquery/schema.py
+++ b/google/cloud/bigquery/schema.py
@@ -360,7 +360,7 @@ def names(self, value):
             if "names" in self._properties:
                 del self._properties["names"]
 
-    def _key(self): 
+    def _key(self):
         """A tuple key that uniquely describes this PolicyTagList.
 
         Used to compute this instance's hashcode and evaluate equality.
@@ -378,9 +378,6 @@ def __eq__(self, other):
     def __ne__(self, other):
         return not self == other
 
-    def __hash__(self):
-        return hash(self._key())
-
     def __repr__(self):
         return "PolicyTagList{}".format(self._key())
 
diff --git a/tests/system.py b/tests/system.py
index dfc9d65fe..49e45c772 100644
--- a/tests/system.py
+++ b/tests/system.py
@@ -387,7 +387,7 @@ def test_create_table_with_policy(self):
         )
 
         table.schema = new_schema
-        table2 = Config.CLIENT.update_table(table, ["schema", ])
+        table2 = Config.CLIENT.update_table(table, ["schema"])
         self.assertEqual(policy_2, table2.schema[1].policy_tags)
 
     def test_create_table_w_time_partitioning_w_clustering_fields(self):
diff --git a/tests/unit/test_schema.py b/tests/unit/test_schema.py
index f0e606b55..202cbc657 100644
--- a/tests/unit/test_schema.py
+++ b/tests/unit/test_schema.py
@@ -718,7 +718,7 @@ def test_setter(self):
         self.assertEqual(policy_tags.names, [])
 
     def test___eq___wrong_type(self):
-        policy = self._make_one(names=["foo", ])
+        policy = self._make_one(names=["foo"])
         other = object()
         self.assertNotEqual(policy, other)
         self.assertEqual(policy, mock.ANY)
@@ -726,4 +726,4 @@ def test___eq___wrong_type(self):
     def test___eq___names_mismatch(self):
         policy = self._make_one(names=["foo", "bar"])
         other = self._make_one(names=["bar", "baz"])
-        self.assertNotEqual(policy, other)
\ No newline at end of file
+        self.assertNotEqual(policy, other)

From 1173bb4b2ccd2aa822fe8dbba333b34073f3e5ef Mon Sep 17 00:00:00 2001
From: Seth Hollyman <shollyman@google.com>
Date: Fri, 15 May 2020 01:27:20 +0000
Subject: [PATCH 14/19] return copy

---
 google/cloud/bigquery/schema.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/google/cloud/bigquery/schema.py b/google/cloud/bigquery/schema.py
index 0ec65c580..d6325a9a7 100644
--- a/google/cloud/bigquery/schema.py
+++ b/google/cloud/bigquery/schema.py
@@ -419,4 +419,4 @@ def to_api_repr(self):
                 A dictionary representing the PolicyTagList object in
                 serialized form.
         """
-        return self._properties
+        return copy.deepcopy(self._properties)

From 3febd454831c101dad5b2a21bd10fdbb3da9585d Mon Sep 17 00:00:00 2001
From: Seth Hollyman <shollyman@google.com>
Date: Fri, 15 May 2020 16:56:27 +0000
Subject: [PATCH 15/19] address api repr feedback

---
 google/cloud/bigquery/schema.py | 4 ++--
 tests/unit/test_schema.py       | 5 +++++
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/google/cloud/bigquery/schema.py b/google/cloud/bigquery/schema.py
index d6325a9a7..550c2b6a6 100644
--- a/google/cloud/bigquery/schema.py
+++ b/google/cloud/bigquery/schema.py
@@ -397,8 +397,8 @@ def from_api_repr(cls, api_repr):
                 what is output by :meth:`to_api_repr`.
 
         Returns:
-            google.cloud.bigquery.schema.PolicyTagList:
-                The ``PolicyTagList`` object.
+            Optional[google.cloud.bigquery.schema.PolicyTagList]:
+                The ``PolicyTagList`` object or None.
         """
         if api_repr is None:
             return None
diff --git a/tests/unit/test_schema.py b/tests/unit/test_schema.py
index 202cbc657..f3168b2e0 100644
--- a/tests/unit/test_schema.py
+++ b/tests/unit/test_schema.py
@@ -701,6 +701,11 @@ def test_from_api_repr(self):
         policy_tags = klass.from_api_repr(api_repr)
         self.assertEqual(policy_tags.to_api_repr(), api_repr)
 
+        # Ensure the None case correctly returns None, rather
+        # than an empty instance.
+        policy_tags2 = klass.from_api_repr(None)
+        self.assertIsNone(policy_tags2)
+
     def test_to_api_repr(self):
         taglist = self._make_one(names=["foo", "bar"])
         self.assertEqual(

From 68af6fee0355d46f7a93b10c78f84e04e16311dc Mon Sep 17 00:00:00 2001
From: Seth Hollyman <shollyman@google.com>
Date: Fri, 15 May 2020 17:39:45 +0000
Subject: [PATCH 16/19] make PolicyTagList fully immutable

---
 google/cloud/bigquery/schema.py | 38 +++++++++++++--------------------
 tests/unit/test_schema.py       | 36 +++++++++++++++++++------------
 2 files changed, 37 insertions(+), 37 deletions(-)

diff --git a/google/cloud/bigquery/schema.py b/google/cloud/bigquery/schema.py
index 550c2b6a6..247a507c5 100644
--- a/google/cloud/bigquery/schema.py
+++ b/google/cloud/bigquery/schema.py
@@ -14,8 +14,6 @@
 
 """Schemas for BigQuery tables / queries."""
 
-import copy
-
 from six.moves import collections_abc
 
 from google.cloud.bigquery_v2 import types
@@ -333,32 +331,21 @@ class PolicyTagList(object):
     """Define Policy Tags for a column.
 
     Args:
-        names (Optional[List[str]]): list of policy tags to associate with
+        names (
+            Optional[List[str]]): list of policy tags to associate with
             the column.  Policy tag identifiers are of the form
             `projects/*/locations/*/taxonomies/*/policyTags/*`.
     """
 
-    def __init__(self, names=None):
+    def __init__(self, names=()):
         self._properties = {}
-        self.names = names
+        self._properties["names"] = tuple(names)
 
     @property
     def names(self):
-        """List[str]: Policy tags associated with this definition.
+        """Tuple[str]: Policy tags associated with this definition.
         """
-        return self._properties.get("names", [])
-
-    @names.setter
-    def names(self, value):
-        """Optional[List[str]]: Policy tags associated with this definition.
-
-        (Defaults to :data:`None`).
-        """
-        if value is not None:
-            self._properties["names"] = value
-        else:
-            if "names" in self._properties:
-                del self._properties["names"]
+        return self._properties.get("names", ())
 
     def _key(self):
         """A tuple key that uniquely describes this PolicyTagList.
@@ -378,6 +365,9 @@ def __eq__(self, other):
     def __ne__(self, other):
         return not self == other
 
+    def __hash__(self):
+        return hash(self._key())
+
     def __repr__(self):
         return "PolicyTagList{}".format(self._key())
 
@@ -402,9 +392,8 @@ def from_api_repr(cls, api_repr):
         """
         if api_repr is None:
             return None
-        instance = cls()
-        instance._properties = copy.deepcopy(api_repr)
-        return instance
+        names = api_repr.get("names", ())
+        return cls(names=names)
 
     def to_api_repr(self):
         """Return a dictionary representing this object.
@@ -419,4 +408,7 @@ def to_api_repr(self):
                 A dictionary representing the PolicyTagList object in
                 serialized form.
         """
-        return copy.deepcopy(self._properties)
+        answer = {}
+        if self.names is not None:
+            answer["names"] = [name for name in self.names]
+        return answer
diff --git a/tests/unit/test_schema.py b/tests/unit/test_schema.py
index f3168b2e0..9f7ee7bb3 100644
--- a/tests/unit/test_schema.py
+++ b/tests/unit/test_schema.py
@@ -82,7 +82,7 @@ def test_to_api_repr(self):
 
         policy = PolicyTagList(names=("foo", "bar"))
         self.assertEqual(
-            policy.to_api_repr(), {"names": ("foo", "bar")},
+            policy.to_api_repr(), {"names": ["foo", "bar"]},
         )
 
         field = self._make_one("foo", "INTEGER", "NULLABLE", policy_tags=policy)
@@ -93,7 +93,7 @@ def test_to_api_repr(self):
                 "name": "foo",
                 "type": "INTEGER",
                 "description": None,
-                "policyTags": {"names": ("foo", "bar")},
+                "policyTags": {"names": ["foo", "bar"]},
             },
         )
 
@@ -149,7 +149,7 @@ def test_from_api_repr_policy(self):
         )
         self.assertEqual(field.name, "foo")
         self.assertEqual(field.field_type, "RECORD")
-        self.assertEqual(field.policy_tags.names, ["one", "two"])
+        self.assertEqual(field.policy_tags.names, ("one", "two"))
         self.assertEqual(len(field.fields), 1)
         self.assertEqual(field.fields[0].name, "bar")
         self.assertEqual(field.fields[0].field_type, "INTEGER")
@@ -693,7 +693,7 @@ def test_constructor(self):
         self.assertIsNotNone(empty_policy_tags.names)
         self.assertEqual(len(empty_policy_tags.names), 0)
         policy_tags = self._make_one(["foo", "bar"])
-        self.assertEqual(policy_tags.names, ["foo", "bar"])
+        self.assertEqual(policy_tags.names, ("foo", "bar"))
 
     def test_from_api_repr(self):
         klass = self._get_target_class()
@@ -711,16 +711,10 @@ def test_to_api_repr(self):
         self.assertEqual(
             taglist.to_api_repr(), {"names": ["foo", "bar"]},
         )
-
-    def test_setter(self):
-        policy_tags = self._make_one()
-        self.assertEqual(policy_tags.names, [])
-        policy_tags.names = None
-        self.assertEqual(policy_tags.names, [])
-        policy_tags.names = ["foo", "bar"]
-        self.assertEqual(policy_tags.names, ["foo", "bar"])
-        policy_tags.names = None
-        self.assertEqual(policy_tags.names, [])
+        taglist2 = self._make_one(names=("foo", "bar"))
+        self.assertEqual(
+            taglist2.to_api_repr(), {"names": ["foo", "bar"]},
+        )
 
     def test___eq___wrong_type(self):
         policy = self._make_one(names=["foo"])
@@ -732,3 +726,17 @@ def test___eq___names_mismatch(self):
         policy = self._make_one(names=["foo", "bar"])
         other = self._make_one(names=["bar", "baz"])
         self.assertNotEqual(policy, other)
+
+    def test___hash__set_equality(self):
+        policy1 = self._make_one(["foo", "bar"])
+        policy2 = self._make_one(["bar", "baz"])
+        set_one = {policy1, policy2}
+        set_two = {policy1, policy2}
+        self.assertEqual(set_one, set_two)
+
+    def test___hash__not_equals(self):
+        policy1 = self._make_one(["foo", "bar"])
+        policy2 = self._make_one(["bar", "baz"])
+        set_one = {policy1}
+        set_two = {policy2}
+        self.assertNotEqual(set_one, set_two)

From c7b06520dbfa47d92951954b9def025f38ac33c4 Mon Sep 17 00:00:00 2001
From: Seth Hollyman <shollyman@google.com>
Date: Fri, 15 May 2020 17:59:54 +0000
Subject: [PATCH 17/19] update docstring

---
 google/cloud/bigquery/schema.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/google/cloud/bigquery/schema.py b/google/cloud/bigquery/schema.py
index 247a507c5..4538e97f6 100644
--- a/google/cloud/bigquery/schema.py
+++ b/google/cloud/bigquery/schema.py
@@ -332,7 +332,7 @@ class PolicyTagList(object):
 
     Args:
         names (
-            Optional[List[str]]): list of policy tags to associate with
+            Optional[Tuple[str]]): list of policy tags to associate with
             the column.  Policy tag identifiers are of the form
             `projects/*/locations/*/taxonomies/*/policyTags/*`.
     """

From fe8061e37dec50ada647fe3a52347eea1ffb2f80 Mon Sep 17 00:00:00 2001
From: Seth Hollyman <shollyman@google.com>
Date: Fri, 15 May 2020 19:39:18 +0000
Subject: [PATCH 18/19] simplify to_api_repr

---
 google/cloud/bigquery/schema.py | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/google/cloud/bigquery/schema.py b/google/cloud/bigquery/schema.py
index 4538e97f6..eb0248dde 100644
--- a/google/cloud/bigquery/schema.py
+++ b/google/cloud/bigquery/schema.py
@@ -408,7 +408,5 @@ def to_api_repr(self):
                 A dictionary representing the PolicyTagList object in
                 serialized form.
         """
-        answer = {}
-        if self.names is not None:
-            answer["names"] = [name for name in self.names]
+        answer = {"names": [name for name in self.names]}
         return answer

From 79d90f87e996a533df5bdbb9f83c53b7ae60e56e Mon Sep 17 00:00:00 2001
From: Seth Hollyman <shollyman@google.com>
Date: Mon, 18 May 2020 16:48:17 +0000
Subject: [PATCH 19/19] remove stale doc comments

---
 google/cloud/bigquery/schema.py | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/google/cloud/bigquery/schema.py b/google/cloud/bigquery/schema.py
index eb0248dde..0eaf1201b 100644
--- a/google/cloud/bigquery/schema.py
+++ b/google/cloud/bigquery/schema.py
@@ -154,11 +154,6 @@ def fields(self):
     def policy_tags(self):
         """Optional[google.cloud.bigquery.schema.PolicyTagList]: Policy tag list
         definition for this field.
-
-        Raises:
-            ValueError:
-                If the value is not :class:`~google.cloud.bigquery.schema.PolicyTagList`
-                or :data:`None`.
         """
         return self._policy_tags