Refs #373 -- Improved test coverage of tuple lookup checks.

This also removed unreachable checks.

2 files changed, 37 insertions, 29 deletions

diff --git a/django/db/models/fields/tuple_lookups.py b/django/db/models/fields/tuple_lookups.py
index 468826f224..d317a69d43 100644
--- a/django/db/models/fields/tuple_lookups.py
+++ b/django/db/models/fields/tuple_lookups.py
@@ -1,7 +1,7 @@
 import itertools
 
 from django.core.exceptions import EmptyResultSet
-from django.db.models.expressions import ColPairs, Func, Value
+from django.db.models.expressions import Func, Value
 from django.db.models.lookups import (
     Exact,
     GreaterThan,
@@ -24,36 +24,14 @@ class TupleLookupMixin:
         return super().get_prep_lookup()
 
     def check_tuple_lookup(self):
-        assert isinstance(self.lhs, ColPairs)
-        self.check_rhs_is_tuple_or_list()
         self.check_rhs_length_equals_lhs_length()
 
-    def check_rhs_is_tuple_or_list(self):
-        if not isinstance(self.rhs, (tuple, list)):
-            raise ValueError(
-                f"'{self.lookup_name}' lookup of '{self.lhs.field.name}' field "
-                "must be a tuple or a list"
-            )
-
     def check_rhs_length_equals_lhs_length(self):
-        if len(self.lhs) != len(self.rhs):
-            raise ValueError(
-                f"'{self.lookup_name}' lookup of '{self.lhs.field.name}' field "
-                f"must have {len(self.lhs)} elements"
-            )
-
-    def check_rhs_is_collection_of_tuples_or_lists(self):
-        if not all(isinstance(vals, (tuple, list)) for vals in self.rhs):
-            raise ValueError(
-                f"'{self.lookup_name}' lookup of '{self.lhs.field.name}' field "
-                f"must be a collection of tuples or lists"
-            )
-
-    def check_rhs_elements_length_equals_lhs_length(self):
-        if not all(len(self.lhs) == len(vals) for vals in self.rhs):
+        len_lhs = len(self.lhs)
+        if len_lhs != len(self.rhs):
             raise ValueError(
                 f"'{self.lookup_name}' lookup of '{self.lhs.field.name}' field "
-                f"must have {len(self.lhs)} elements each"
+                f"must have {len_lhs} elements"
             )
 
     def as_sql(self, compiler, connection):
@@ -192,11 +170,16 @@ class TupleLessThanOrEqual(TupleLookupMixin, LessThanOrEqual):
 
 class TupleIn(TupleLookupMixin, In):
     def check_tuple_lookup(self):
-        assert isinstance(self.lhs, ColPairs)
-        self.check_rhs_is_tuple_or_list()
-        self.check_rhs_is_collection_of_tuples_or_lists()
         self.check_rhs_elements_length_equals_lhs_length()
 
+    def check_rhs_elements_length_equals_lhs_length(self):
+        len_lhs = len(self.lhs)
+        if not all(len_lhs == len(vals) for vals in self.rhs):
+            raise ValueError(
+                f"'{self.lookup_name}' lookup of '{self.lhs.field.name}' field "
+                f"must have {len_lhs} elements each"
+            )
+
     def as_sql(self, compiler, connection):
         if not self.rhs:
             raise EmptyResultSet
diff --git a/tests/foreign_object/test_tuple_lookups.py b/tests/foreign_object/test_tuple_lookups.py
index cf080d084b..2742d6e93d 100644
--- a/tests/foreign_object/test_tuple_lookups.py
+++ b/tests/foreign_object/test_tuple_lookups.py
@@ -240,3 +240,28 @@ class TupleLookupsTests(TestCase):
             self.assertSequenceEqual(
                 Contact.objects.filter(customer__isnull=subquery).order_by("id"), ()
             )
+
+    def test_lookup_errors(self):
+        m_2_elements = "'%s' lookup of 'customer' field must have 2 elements"
+        m_2_elements_each = "'in' lookup of 'customer' field must have 2 elements each"
+        test_cases = (
+            ({"customer": 1}, m_2_elements % "exact"),
+            ({"customer": (1, 2, 3)}, m_2_elements % "exact"),
+            ({"customer__in": (1, 2, 3)}, m_2_elements_each),
+            ({"customer__in": ("foo", "bar")}, m_2_elements_each),
+            ({"customer__gt": 1}, m_2_elements % "gt"),
+            ({"customer__gt": (1, 2, 3)}, m_2_elements % "gt"),
+            ({"customer__gte": 1}, m_2_elements % "gte"),
+            ({"customer__gte": (1, 2, 3)}, m_2_elements % "gte"),
+            ({"customer__lt": 1}, m_2_elements % "lt"),
+            ({"customer__lt": (1, 2, 3)}, m_2_elements % "lt"),
+            ({"customer__lte": 1}, m_2_elements % "lte"),
+            ({"customer__lte": (1, 2, 3)}, m_2_elements % "lte"),
+        )
+
+        for kwargs, message in test_cases:
+            with (
+                self.subTest(kwargs=kwargs),
+                self.assertRaisesMessage(ValueError, message),
+            ):
+                Contact.objects.get(**kwargs)