Merge pull request #111 from uncovertruth/feature/migrate_to_complement

Migrate to complement

HISTORY.rst

@@ -7,6 +7,7 @@ History
 
 - Add support for Django 2.1
 - Add support for Python 3.7
+- Migrate to `complement` from `exists` and `neexists`
 
 0.1.0
 -----

README.rst

@@ -102,11 +102,10 @@ neexact is negate exact, neiexact is negate iexact, others are similar.
 - neregex
 - neiregex
 
-Exists
-^^^^^^
+Complement
+^^^^^^^^^^
 
-- exists
-- neexists
+- complement
 
 Extra regexes
 ^^^^^^^^^^^^^

lookup_extensions/__init__.py

@@ -2,6 +2,6 @@
 
 __author__ = """UNCOVER TRUTH Inc."""
 __email__ = '[email protected]'
-__version__ = '0.1.1'
+__version__ = '0.2.0'
 
 default_app_config = 'lookup_extensions.apps.LookupExtensionsConfig'

lookup_extensions/lookups/__init__.py

@@ -1,2 +1,3 @@
+from .exists import *  # noqa F401,F403
 from .exregex import *  # noqa F401,F403
 from .negate import *  # noqa F401,F403

lookup_extensions/lookups/exists.py

@@ -0,0 +1,24 @@
+from django.db.models import Exists
+from django.db.models.fields import Field
+from django.db.models.lookups import (
+    BuiltinLookup,
+    FieldGetDbPrepValueMixin,
+)
+
+
+@Field.register_lookup
+class Complement(FieldGetDbPrepValueMixin, BuiltinLookup):
+    lookup_name = 'complement'
+
+    def process_rhs(self, compiler, connection):
+        if self.rhs_is_direct_value() or not isinstance(self.rhs, Exists):
+            raise ValueError("Exists subqueries are required")
+
+        db_rhs = getattr(self.rhs, '_db', None)
+        if db_rhs is not None and db_rhs != connection.alias:
+            raise ValueError("Subqueries aren't allowed across different databases")
+
+        return super(Complement, self).process_rhs(compiler, connection)
+
+    def as_sql(self, compiler, connection):
+        return self.process_rhs(compiler, connection)

lookup_extensions/sql.py

@@ -1,20 +1,15 @@
-from django.core.exceptions import FieldError
-from django.db.models import Exists
 from django.db.models.constants import LOOKUP_SEP
 from django.db.models.sql import Query as DjangoQuery
 
 
 class ExtendedQueryMixin(object):
     SUBQUERY_LOOKUPS = (
-        'exists',
-        'neexists',
+        'complement',
     )
 
     def build_lookup(self, lookups, lhs, rhs):
         if lookups and lookups[-1] in self.SUBQUERY_LOOKUPS:
-            if not isinstance(rhs, Exists):
-                raise FieldError("Value is not Subquery instance.")
-            return super(ExtendedQueryMixin, self).build_lookup(['exact'], rhs, not lookups[-1].startswith('ne'))
+            return super(ExtendedQueryMixin, self).build_lookup(lookups[-1:], rhs, rhs)
         return super(ExtendedQueryMixin, self).build_lookup(lookups, lhs, rhs)
 
     def prepare_lookup_value(self, value, lookups, can_reuse, allow_joins=True):

tests/test_lookup/tests.py

@@ -1168,20 +1168,20 @@ def test_negate_exregex_short_end_escapes(self):
             ],
         )
 
-    def test_exists(self):
+    def test_complement(self):
         tags = Tag.objects.filter(articles=OuterRef('id'), name='Tag 2')
         self.assertQuerysetEqual(
-            Article.objects.filter(tag__exists=Exists(tags)).filter(author=self.au1),
+            Article.objects.filter(tag__complement=Exists(tags)).filter(author=self.au1),
             [
                 '<Article: Article 4>',
                 '<Article: Article 3>',
             ],
         )
 
-    def test_neexists(self):
+    def test_negate_complement(self):
         tags = Tag.objects.filter(articles=OuterRef('id'), name='Tag 2')
         self.assertQuerysetEqual(
-            Article.objects.filter(tag__neexists=Exists(tags)).filter(author=self.au1),
+            Article.objects.filter(tag__complement=~Exists(tags)).filter(author=self.au1),
             [
                 '<Article: Article 2>',
                 '<Article: Article 1>',