Fixed #24920 -- Added support for DecimalField with no precision.

Thanks Lily for the review.

3 files changed, 70 insertions, 12 deletions

diff --git a/tests/inspectdb/models.py b/tests/inspectdb/models.py
index 3d6388a7be..fbe1df8a95 100644
--- a/tests/inspectdb/models.py
+++ b/tests/inspectdb/models.py
@@ -121,6 +121,15 @@ class CharFieldUnlimited(models.Model):
         required_db_features = {"supports_unlimited_charfield"}
 
 
+class DecimalFieldNoPrec(models.Model):
+    decimal_field_no_precision = models.DecimalField(
+        max_digits=None, decimal_places=None
+    )
+
+    class Meta:
+        required_db_features = {"supports_no_precision_decimalfield"}
+
+
 class UniqueTogether(models.Model):
     field1 = models.IntegerField()
     field2 = models.CharField(max_length=10)
diff --git a/tests/inspectdb/tests.py b/tests/inspectdb/tests.py
index 9104671b4f..c16258b0eb 100644
--- a/tests/inspectdb/tests.py
+++ b/tests/inspectdb/tests.py
@@ -202,6 +202,13 @@ class InspectDBTestCase(TestCase):
         output = out.getvalue()
         self.assertIn("char_field = models.CharField()", output)
 
+    @skipUnlessDBFeature("supports_no_precision_decimalfield")
+    def test_decimal_field_no_precision(self):
+        out = StringIO()
+        call_command("inspectdb", "inspectdb_decimalfieldnoprec", stdout=out)
+        output = out.getvalue()
+        self.assertIn("decimal_field_no_precision = models.DecimalField()", output)
+
     def test_number_field_types(self):
         """Test introspection of various Django field types"""
         assertFieldType = self.make_field_type_asserter()
@@ -228,13 +235,8 @@ class InspectDBTestCase(TestCase):
             assertFieldType(
                 "decimal_field", "models.DecimalField(max_digits=6, decimal_places=1)"
             )
-        else:  # Guessed arguments on SQLite, see #5014
-            assertFieldType(
-                "decimal_field",
-                "models.DecimalField(max_digits=10, decimal_places=5)  "
-                "# max_digits and decimal_places have been guessed, "
-                "as this database handles decimal fields as float",
-            )
+        else:
+            assertFieldType("decimal_field", "models.DecimalField()")
 
         assertFieldType("float_field", "models.FloatField()")
         assertFieldType(
diff --git a/tests/invalid_models_tests/test_ordinary_fields.py b/tests/invalid_models_tests/test_ordinary_fields.py
index 1fcf3f708d..2c2653a538 100644
--- a/tests/invalid_models_tests/test_ordinary_fields.py
+++ b/tests/invalid_models_tests/test_ordinary_fields.py
@@ -599,15 +599,16 @@ class DateTimeFieldTests(SimpleTestCase):
 
 
 @isolate_apps("invalid_models_tests")
-class DecimalFieldTests(SimpleTestCase):
-    def test_required_attributes(self):
+class DecimalFieldTests(TestCase):
+    def test_both_attributes_omitted(self):
         class Model(models.Model):
             field = models.DecimalField()
 
         field = Model._meta.get_field("field")
-        self.assertEqual(
-            field.check(),
-            [
+        if connection.features.supports_no_precision_decimalfield:
+            expected = []
+        else:
+            expected = [
                 Error(
                     "DecimalFields must define a 'decimal_places' attribute.",
                     obj=field,
@@ -618,6 +619,52 @@ class DecimalFieldTests(SimpleTestCase):
                     obj=field,
                     id="fields.E132",
                 ),
+            ]
+        self.assertEqual(field.check(), expected)
+
+    def test_both_attributes_omitted_required_db_features(self):
+        class Model(models.Model):
+            field = models.DecimalField()
+
+            class Meta:
+                required_db_features = {"supports_no_precision_decimalfield"}
+
+        field = Model._meta.get_field("field")
+        self.assertEqual(field.check(databases=self.databases), [])
+
+    @skipUnlessDBFeature("supports_no_precision_decimalfield")
+    def test_only_max_digits_defined(self):
+        class Model(models.Model):
+            field = models.DecimalField(max_digits=13)
+
+        field = Model._meta.get_field("field")
+        self.assertEqual(
+            field.check(),
+            [
+                Error(
+                    "DecimalField’s max_digits and decimal_places must both "
+                    "be defined or both omitted.",
+                    obj=field,
+                    id="fields.E135",
+                ),
+            ],
+        )
+
+    @skipUnlessDBFeature("supports_no_precision_decimalfield")
+    def test_only_decimal_places_defined(self):
+        class Model(models.Model):
+            field = models.DecimalField(decimal_places=5)
+
+        field = Model._meta.get_field("field")
+        self.assertEqual(
+            field.check(),
+            [
+                Error(
+                    "DecimalField’s max_digits and decimal_places must both "
+                    "be defined or both omitted.",
+                    obj=field,
+                    id="fields.E135",
+                ),
             ],
         )