Fixed #28353 -- Fixed some GIS functions when queryset is evaluated more than once.

Reverted test for refs #27603 in favor of using FuncTestMixin.

12 files changed, 175 insertions, 85 deletions

diff --git a/django/contrib/gis/db/backends/base/operations.py b/django/contrib/gis/db/backends/base/operations.py
index 170775f063..af85b83df6 100644
--- a/django/contrib/gis/db/backends/base/operations.py
+++ b/django/contrib/gis/db/backends/base/operations.py
@@ -1,5 +1,8 @@
 from django.contrib.gis.db.models import GeometryField
 from django.contrib.gis.db.models.functions import Distance
+from django.contrib.gis.measure import (
+    Area as AreaMeasure, Distance as DistanceMeasure,
+)
 from django.utils.functional import cached_property
 
 
@@ -135,3 +138,24 @@ class BaseSpatialOperations:
             'Subclasses of BaseSpatialOperations must provide a '
             'get_geometry_converter() method.'
         )
+
+    def get_area_att_for_field(self, field):
+        if field.geodetic(self.connection):
+            if self.connection.features.supports_area_geodetic:
+                return 'sq_m'
+            raise NotImplementedError('Area on geodetic coordinate systems not supported.')
+        else:
+            units_name = field.units_name(self.connection)
+            if units_name:
+                return AreaMeasure.unit_attname(units_name)
+
+    def get_distance_att_for_field(self, field):
+        dist_att = None
+        if field.geodetic(self.connection):
+            if self.connection.features.supports_distance_geodetic:
+                dist_att = 'm'
+        else:
+            units = field.units_name(self.connection)
+            if units:
+                dist_att = DistanceMeasure.unit_attname(units)
+        return dist_att
diff --git a/django/contrib/gis/db/backends/oracle/operations.py b/django/contrib/gis/db/backends/oracle/operations.py
index e69b8b8c07..19cf2eaa06 100644
--- a/django/contrib/gis/db/backends/oracle/operations.py
+++ b/django/contrib/gis/db/backends/oracle/operations.py
@@ -212,3 +212,6 @@ class OracleOperations(BaseSpatialOperations, DatabaseOperations):
                     geom.srid = srid
                 return geom
         return converter
+
+    def get_area_att_for_field(self, field):
+        return 'sq_m'
diff --git a/django/contrib/gis/db/backends/postgis/operations.py b/django/contrib/gis/db/backends/postgis/operations.py
index a535b49849..51c8d5006e 100644
--- a/django/contrib/gis/db/backends/postgis/operations.py
+++ b/django/contrib/gis/db/backends/postgis/operations.py
@@ -389,3 +389,6 @@ class PostGISOperations(BaseSpatialOperations, DatabaseOperations):
         def converter(value, expression, connection):
             return None if value is None else GEOSGeometryBase(read(value), geom_class)
         return converter
+
+    def get_area_att_for_field(self, field):
+        return 'sq_m'
diff --git a/django/contrib/gis/db/models/functions.py b/django/contrib/gis/db/models/functions.py
index e166c21e29..9d245b93c4 100644
--- a/django/contrib/gis/db/models/functions.py
+++ b/django/contrib/gis/db/models/functions.py
@@ -3,9 +3,6 @@ from decimal import Decimal
 from django.contrib.gis.db.models.fields import BaseSpatialField, GeometryField
 from django.contrib.gis.db.models.sql import AreaField, DistanceField
 from django.contrib.gis.geometry.backend import Geometry
-from django.contrib.gis.measure import (
-    Area as AreaMeasure, Distance as DistanceMeasure,
-)
 from django.core.exceptions import FieldError
 from django.db.models import (
     BooleanField, FloatField, IntegerField, TextField, Transform,
@@ -121,30 +118,17 @@ class OracleToleranceMixin:
 
 
 class Area(OracleToleranceMixin, GeoFunc):
-    output_field_class = AreaField
     arity = 1
 
+    @cached_property
+    def output_field(self):
+        return AreaField(self.geo_field)
+
     def as_sql(self, compiler, connection, **extra_context):
-        if connection.ops.geography:
-            self.output_field.area_att = 'sq_m'
-        else:
-            # Getting the area units of the geographic field.
-            if self.geo_field.geodetic(connection):
-                if connection.features.supports_area_geodetic:
-                    self.output_field.area_att = 'sq_m'
-                else:
-                    # TODO: Do we want to support raw number areas for geodetic fields?
-                    raise NotImplementedError('Area on geodetic coordinate systems not supported.')
-            else:
-                units_name = self.geo_field.units_name(connection)
-                if units_name:
-                    self.output_field.area_att = AreaMeasure.unit_attname(units_name)
+        if not connection.features.supports_area_geodetic and self.geo_field.geodetic(connection):
+            raise NotImplementedError('Area on geodetic coordinate systems not supported.')
         return super().as_sql(compiler, connection, **extra_context)
 
-    def as_oracle(self, compiler, connection):
-        self.output_field = AreaField('sq_m')  # Oracle returns area in units of meters.
-        return super().as_oracle(compiler, connection)
-
     def as_sqlite(self, compiler, connection, **extra_context):
         if self.geo_field.geodetic(connection):
             extra_context['template'] = '%(function)s(%(expressions)s, %(spheroid)d)'
@@ -237,27 +221,13 @@ class Difference(OracleToleranceMixin, GeomOutputGeoFunc):
 
 
 class DistanceResultMixin:
-    output_field_class = DistanceField
+    @cached_property
+    def output_field(self):
+        return DistanceField(self.geo_field)
 
     def source_is_geography(self):
         return self.geo_field.geography and self.geo_field.srid == 4326
 
-    def distance_att(self, connection):
-        dist_att = None
-        if self.geo_field.geodetic(connection):
-            if connection.features.supports_distance_geodetic:
-                dist_att = 'm'
-        else:
-            units = self.geo_field.units_name(connection)
-            if units:
-                dist_att = DistanceMeasure.unit_attname(units)
-        return dist_att
-
-    def as_sql(self, compiler, connection, **extra_context):
-        clone = self.copy()
-        clone.output_field.distance_att = self.distance_att(connection)
-        return super(DistanceResultMixin, clone).as_sql(compiler, connection, **extra_context)
-
 
 class Distance(DistanceResultMixin, OracleToleranceMixin, GeoFunc):
     geom_param_pos = (0, 1)
@@ -266,19 +236,19 @@ class Distance(DistanceResultMixin, OracleToleranceMixin, GeoFunc):
     def __init__(self, expr1, expr2, spheroid=None, **extra):
         expressions = [expr1, expr2]
         if spheroid is not None:
-            self.spheroid = spheroid
-            expressions += (self._handle_param(spheroid, 'spheroid', bool),)
+            self.spheroid = self._handle_param(spheroid, 'spheroid', bool)
         super().__init__(*expressions, **extra)
 
     def as_postgresql(self, compiler, connection):
+        clone = self.copy()
         function = None
-        expr2 = self.source_expressions[1]
+        expr2 = clone.source_expressions[1]
         geography = self.source_is_geography()
         if expr2.output_field.geography != geography:
             if isinstance(expr2, Value):
                 expr2.output_field.geography = geography
             else:
-                self.source_expressions[1] = Cast(
+                clone.source_expressions[1] = Cast(
                     expr2,
                     GeometryField(srid=expr2.output_field.srid, geography=geography),
                 )
@@ -289,19 +259,12 @@ class Distance(DistanceResultMixin, OracleToleranceMixin, GeoFunc):
                 # DistanceSpheroid is more accurate and resource intensive than DistanceSphere
                 function = connection.ops.spatial_function_name('DistanceSpheroid')
                 # Replace boolean param by the real spheroid of the base field
-                self.source_expressions[2] = Value(self.geo_field.spheroid(connection))
+                clone.source_expressions.append(Value(self.geo_field.spheroid(connection)))
             else:
                 function = connection.ops.spatial_function_name('DistanceSphere')
-        return super().as_sql(compiler, connection, function=function)
-
-    def as_oracle(self, compiler, connection):
-        if self.spheroid:
-            self.source_expressions.pop(2)
-        return super().as_oracle(compiler, connection)
+        return super(Distance, clone).as_sql(compiler, connection, function=function)
 
     def as_sqlite(self, compiler, connection, **extra_context):
-        if self.spheroid:
-            self.source_expressions.pop(2)
         if self.geo_field.geodetic(connection):
             # SpatiaLite returns NULL instead of zero on geodetic coordinates
             extra_context['template'] = 'COALESCE(%(function)s(%(expressions)s, %(spheroid)s), 0)'
@@ -360,18 +323,19 @@ class Length(DistanceResultMixin, OracleToleranceMixin, GeoFunc):
         return super().as_sql(compiler, connection, **extra_context)
 
     def as_postgresql(self, compiler, connection):
+        clone = self.copy()
         function = None
         if self.source_is_geography():
-            self.source_expressions.append(Value(self.spheroid))
+            clone.source_expressions.append(Value(self.spheroid))
         elif self.geo_field.geodetic(connection):
             # Geometry fields with geodetic (lon/lat) coordinates need length_spheroid
             function = connection.ops.spatial_function_name('LengthSpheroid')
-            self.source_expressions.append(Value(self.geo_field.spheroid(connection)))
+            clone.source_expressions.append(Value(self.geo_field.spheroid(connection)))
         else:
             dim = min(f.dim for f in self.get_source_fields() if f)
             if dim > 2:
                 function = connection.ops.length3d
-        return super().as_sql(compiler, connection, function=function)
+        return super(Length, clone).as_sql(compiler, connection, function=function)
 
     def as_sqlite(self, compiler, connection):
         function = None
@@ -482,10 +446,11 @@ class Transform(GeomOutputGeoFunc):
 
 class Translate(Scale):
     def as_sqlite(self, compiler, connection):
+        clone = self.copy()
         if len(self.source_expressions) < 4:
             # Always provide the z parameter for ST_Translate
-            self.source_expressions.append(Value(0))
-        return super().as_sqlite(compiler, connection)
+            clone.source_expressions.append(Value(0))
+        return super(Translate, clone).as_sqlite(compiler, connection)
 
 
 class Union(OracleToleranceMixin, GeomOutputGeoFunc):
diff --git a/django/contrib/gis/db/models/sql/conversion.py b/django/contrib/gis/db/models/sql/conversion.py
index eafa7b5d17..99ab51e239 100644
--- a/django/contrib/gis/db/models/sql/conversion.py
+++ b/django/contrib/gis/db/models/sql/conversion.py
@@ -10,9 +10,9 @@ from django.db import models
 
 class AreaField(models.FloatField):
     "Wrapper for Area values."
-    def __init__(self, area_att=None):
+    def __init__(self, geo_field):
         super().__init__()
-        self.area_att = area_att
+        self.geo_field = geo_field
 
     def get_prep_value(self, value):
         if not isinstance(value, Area):
@@ -20,19 +20,21 @@ class AreaField(models.FloatField):
         return value
 
     def get_db_prep_value(self, value, connection, prepared=False):
-        if value is None or not self.area_att:
-            return value
-        return getattr(value, self.area_att)
+        if value is None:
+            return
+        area_att = connection.ops.get_area_att_for_field(self.geo_field)
+        return getattr(value, area_att) if area_att else value
 
     def from_db_value(self, value, expression, connection):
+        if value is None:
+            return
         # If the database returns a Decimal, convert it to a float as expected
         # by the Python geometric objects.
         if isinstance(value, Decimal):
             value = float(value)
         # If the units are known, convert value into area measure.
-        if value is not None and self.area_att:
-            value = Area(**{self.area_att: value})
-        return value
+        area_att = connection.ops.get_area_att_for_field(self.geo_field)
+        return Area(**{area_att: value}) if area_att else value
 
     def get_internal_type(self):
         return 'AreaField'
@@ -40,9 +42,9 @@ class AreaField(models.FloatField):
 
 class DistanceField(models.FloatField):
     "Wrapper for Distance values."
-    def __init__(self, distance_att=None):
+    def __init__(self, geo_field):
         super().__init__()
-        self.distance_att = distance_att
+        self.geo_field = geo_field
 
     def get_prep_value(self, value):
         if isinstance(value, Distance):
@@ -52,14 +54,16 @@ class DistanceField(models.FloatField):
     def get_db_prep_value(self, value, connection, prepared=False):
         if not isinstance(value, Distance):
             return value
-        if not self.distance_att:
+        distance_att = connection.ops.get_distance_att_for_field(self.geo_field)
+        if not distance_att:
             raise ValueError('Distance measure is supplied, but units are unknown for result.')
-        return getattr(value, self.distance_att)
+        return getattr(value, distance_att)
 
     def from_db_value(self, value, expression, connection):
-        if value is None or not self.distance_att:
-            return value
-        return Distance(**{self.distance_att: value})
+        if value is None:
+            return
+        distance_att = connection.ops.get_distance_att_for_field(self.geo_field)
+        return Distance(**{distance_att: value}) if distance_att else value
 
     def get_internal_type(self):
         return 'DistanceField'
diff --git a/tests/gis_tests/distapp/tests.py b/tests/gis_tests/distapp/tests.py
index 395f7226ef..d162759513 100644
--- a/tests/gis_tests/distapp/tests.py
+++ b/tests/gis_tests/distapp/tests.py
@@ -9,7 +9,9 @@ from django.db import connection
 from django.db.models import F, Q
 from django.test import TestCase, skipIfDBFeature, skipUnlessDBFeature
 
-from ..utils import mysql, no_oracle, oracle, postgis, spatialite
+from ..utils import (
+    FuncTestMixin, mysql, no_oracle, oracle, postgis, spatialite,
+)
 from .models import (
     AustraliaCity, CensusZipcode, Interstate, SouthTexasCity, SouthTexasCityFt,
     SouthTexasInterstate, SouthTexasZipcode,
@@ -262,7 +264,7 @@ Perimeter(geom1)                                |    OK              |      :-(
 '''  # NOQA
 
 
-class DistanceFunctionsTests(TestCase):
+class DistanceFunctionsTests(FuncTestMixin, TestCase):
     fixtures = ['initial']
 
     @skipUnlessDBFeature("has_Area_function")
diff --git a/tests/gis_tests/geo3d/tests.py b/tests/gis_tests/geo3d/tests.py
index 39603d1249..d2e85f0607 100644
--- a/tests/gis_tests/geo3d/tests.py
+++ b/tests/gis_tests/geo3d/tests.py
@@ -8,6 +8,7 @@ from django.contrib.gis.db.models.functions import (
 from django.contrib.gis.geos import GEOSGeometry, LineString, Point, Polygon
 from django.test import TestCase, skipUnlessDBFeature
 
+from ..utils import FuncTestMixin
 from .models import (
     City3D, Interstate2D, Interstate3D, InterstateProj2D, InterstateProj3D,
     MultiPoint3D, Point2D, Point3D, Polygon2D, Polygon3D,
@@ -205,7 +206,7 @@ class Geo3DTest(Geo3DLoadingHelper, TestCase):
 
 
 @skipUnlessDBFeature("supports_3d_functions")
-class Geo3DFunctionsTests(Geo3DLoadingHelper, TestCase):
+class Geo3DFunctionsTests(FuncTestMixin, Geo3DLoadingHelper, TestCase):
     def test_kml(self):
         """
         Test KML() function with Z values.
diff --git a/tests/gis_tests/geoapp/test_functions.py b/tests/gis_tests/geoapp/test_functions.py
index bb13d9e37f..cdd05d78ff 100644
--- a/tests/gis_tests/geoapp/test_functions.py
+++ b/tests/gis_tests/geoapp/test_functions.py
@@ -12,11 +12,11 @@ from django.db import connection
 from django.db.models import Sum
 from django.test import TestCase, skipUnlessDBFeature
 
-from ..utils import mysql, oracle, postgis, spatialite
+from ..utils import FuncTestMixin, mysql, oracle, postgis, spatialite
 from .models import City, Country, CountryWebMercator, State, Track
 
 
-class GISFunctionsTests(TestCase):
+class GISFunctionsTests(FuncTestMixin, TestCase):
     """
     Testing functions from django/contrib/gis/db/models/functions.py.
     Area/Distance/Length/Perimeter are tested in distapp/tests.
@@ -127,11 +127,8 @@ class GISFunctionsTests(TestCase):
             City.objects.annotate(kml=functions.AsKML('name'))
 
         # Ensuring the KML is as expected.
-        qs = City.objects.annotate(kml=functions.AsKML('point', precision=9))
-        ptown = qs.get(name='Pueblo')
+        ptown = City.objects.annotate(kml=functions.AsKML('point', precision=9)).get(name='Pueblo')
         self.assertEqual('<Point><coordinates>-104.609252,38.255001</coordinates></Point>', ptown.kml)
-        # Same result if the queryset is evaluated again.
-        self.assertEqual(qs.get(name='Pueblo').kml, ptown.kml)
 
     @skipUnlessDBFeature("has_AsSVG_function")
     def test_assvg(self):
diff --git a/tests/gis_tests/geogapp/tests.py b/tests/gis_tests/geogapp/tests.py
index 2969ca1cc6..c9986fd78b 100644
--- a/tests/gis_tests/geogapp/tests.py
+++ b/tests/gis_tests/geogapp/tests.py
@@ -11,7 +11,7 @@ from django.db import connection
 from django.db.models.functions import Cast
 from django.test import TestCase, skipIfDBFeature, skipUnlessDBFeature
 
-from ..utils import oracle, postgis, spatialite
+from ..utils import FuncTestMixin, oracle, postgis, spatialite
 from .models import City, County, Zipcode
 
 
@@ -86,7 +86,7 @@ class GeographyTest(TestCase):
             self.assertEqual(state, c.state)
 
 
-class GeographyFunctionTests(TestCase):
+class GeographyFunctionTests(FuncTestMixin, TestCase):
     fixtures = ['initial']
 
     @skipUnlessDBFeature("supports_extent_aggr")
diff --git a/tests/gis_tests/test_fields.py b/tests/gis_tests/test_fields.py
index fb0c953f21..27db3e1dfa 100644
--- a/tests/gis_tests/test_fields.py
+++ b/tests/gis_tests/test_fields.py
@@ -7,9 +7,9 @@ from django.test import SimpleTestCase
 class FieldsTests(SimpleTestCase):
 
     def test_area_field_deepcopy(self):
-        field = AreaField()
+        field = AreaField(None)
         self.assertEqual(copy.deepcopy(field), field)
 
     def test_distance_field_deepcopy(self):
-        field = DistanceField()
+        field = DistanceField(None)
         self.assertEqual(copy.deepcopy(field), field)
diff --git a/tests/gis_tests/test_gis_tests_utils.py b/tests/gis_tests/test_gis_tests_utils.py
new file mode 100644
index 0000000000..32d072fd9b
--- /dev/null
+++ b/tests/gis_tests/test_gis_tests_utils.py
@@ -0,0 +1,52 @@
+from django.db import connection, models
+from django.db.models.expressions import Func
+from django.test import SimpleTestCase
+
+from .utils import FuncTestMixin
+
+
+def test_mutation(raises=True):
+    def wrapper(mutation_func):
+        def test(test_case_instance, *args, **kwargs):
+            class TestFunc(Func):
+                output_field = models.IntegerField()
+
+                def __init__(self):
+                    self.attribute = 'initial'
+                    super().__init__('initial', ['initial'])
+
+                def as_sql(self, *args, **kwargs):
+                    mutation_func(self)
+                    return '', ()
+
+            if raises:
+                msg = 'TestFunc Func was mutated during compilation.'
+                with test_case_instance.assertRaisesMessage(AssertionError, msg):
+                    getattr(TestFunc(), 'as_' + connection.vendor)(None, None)
+            else:
+                getattr(TestFunc(), 'as_' + connection.vendor)(None, None)
+
+        return test
+    return wrapper
+
+
+class FuncTestMixinTests(FuncTestMixin, SimpleTestCase):
+    @test_mutation()
+    def test_mutated_attribute(func):
+        func.attribute = 'mutated'
+
+    @test_mutation()
+    def test_mutated_expressions(func):
+        func.source_expressions.clear()
+
+    @test_mutation()
+    def test_mutated_expression(func):
+        func.source_expressions[0].name = 'mutated'
+
+    @test_mutation()
+    def test_mutated_expression_deep(func):
+        func.source_expressions[1].value[0] = 'mutated'
+
+    @test_mutation(raises=False)
+    def test_not_mutated(func):
+        pass
diff --git a/tests/gis_tests/utils.py b/tests/gis_tests/utils.py
index 6eb029c1d5..b30da7e40d 100644
--- a/tests/gis_tests/utils.py
+++ b/tests/gis_tests/utils.py
@@ -1,8 +1,11 @@
+import copy
 import unittest
 from functools import wraps
+from unittest import mock
 
 from django.conf import settings
 from django.db import DEFAULT_DB_ALIAS, connection
+from django.db.models.expressions import Func
 
 
 def skipUnlessGISLookup(*gis_lookups):
@@ -56,3 +59,39 @@ elif spatialite:
     from django.contrib.gis.db.backends.spatialite.models import SpatialiteSpatialRefSys as SpatialRefSys
 else:
     SpatialRefSys = None
+
+
+class FuncTestMixin:
+    """Assert that Func expressions aren't mutated during their as_sql()."""
+    def setUp(self):
+        def as_sql_wrapper(original_as_sql):
+            def inner(*args, **kwargs):
+                func = original_as_sql.__self__
+                # Resolve output_field before as_sql() so touching it in
+                # as_sql() won't change __dict__.
+                func.output_field
+                __dict__original = copy.deepcopy(func.__dict__)
+                result = original_as_sql(*args, **kwargs)
+                msg = '%s Func was mutated during compilation.' % func.__class__.__name__
+                self.assertEqual(func.__dict__, __dict__original, msg)
+                return result
+            return inner
+
+        def __getattribute__(self, name):
+            if name != vendor_impl:
+                return __getattribute__original(self, name)
+            try:
+                as_sql = __getattribute__original(self, vendor_impl)
+            except AttributeError:
+                as_sql = __getattribute__original(self, 'as_sql')
+            return as_sql_wrapper(as_sql)
+
+        vendor_impl = 'as_' + connection.vendor
+        __getattribute__original = Func.__getattribute__
+        self.func_patcher = mock.patch.object(Func, '__getattribute__', __getattribute__)
+        self.func_patcher.start()
+        super().setUp()
+
+    def tearDown(self):
+        super().tearDown()
+        self.func_patcher.stop()