From 1d4cbee39af2ec772d43a146ca724d34613c6a76 Mon Sep 17 00:00:00 2001
From: Olivier Dalang <olivier.dalang@gmail.com>
Date: Fri, 11 Aug 2023 16:06:07 +0200
Subject: [PATCH] contribute to constraints test - minimal

---
 tests/contribute_to_meta/__init__.py          |  0
 tests/contribute_to_meta/fields.py            | 14 ++++++
 .../contribute_to_meta/migrations/.gitignore  |  1 +
 .../contribute_to_meta/migrations/__init__.py |  0
 tests/contribute_to_meta/models.py            | 14 ++++++
 tests/contribute_to_meta/tests.py             | 49 +++++++++++++++++++
 6 files changed, 78 insertions(+)
 create mode 100644 tests/contribute_to_meta/__init__.py
 create mode 100644 tests/contribute_to_meta/fields.py
 create mode 100644 tests/contribute_to_meta/migrations/.gitignore
 create mode 100644 tests/contribute_to_meta/migrations/__init__.py
 create mode 100644 tests/contribute_to_meta/models.py
 create mode 100644 tests/contribute_to_meta/tests.py

diff --git a/tests/contribute_to_meta/__init__.py b/tests/contribute_to_meta/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/tests/contribute_to_meta/fields.py b/tests/contribute_to_meta/fields.py
new file mode 100644
index 0000000000..9bf530c838
--- /dev/null
+++ b/tests/contribute_to_meta/fields.py
@@ -0,0 +1,14 @@
+from django.db import models
+
+
+class ConstraintField(models.CharField):
+    """A field that contributes a DB contraint to the model's Meta"""
+
+    def contribute_to_class(self, cls, name, private_only=False):
+        super().contribute_to_class(cls, name, private_only)
+        cls._meta.constraints.append(
+            models.CheckConstraint(
+                check=models.Q(**{name: "valid"}),
+                name=f"test_constraint_{cls.__name__.lower()}",
+            )
+        )
diff --git a/tests/contribute_to_meta/migrations/.gitignore b/tests/contribute_to_meta/migrations/.gitignore
new file mode 100644
index 0000000000..26a35de2cd
--- /dev/null
+++ b/tests/contribute_to_meta/migrations/.gitignore
@@ -0,0 +1 @@
+0001_initial.py
diff --git a/tests/contribute_to_meta/migrations/__init__.py b/tests/contribute_to_meta/migrations/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/tests/contribute_to_meta/models.py b/tests/contribute_to_meta/models.py
new file mode 100644
index 0000000000..d680fa3574
--- /dev/null
+++ b/tests/contribute_to_meta/models.py
@@ -0,0 +1,14 @@
+from django.db import models
+
+from .fields import ConstraintField
+
+
+class ModelA(models.Model):
+    field = ConstraintField(max_length=10)
+
+
+class ModelC(models.Model):
+    class Meta:
+        constraints = []
+
+    field = ConstraintField(max_length=10)
diff --git a/tests/contribute_to_meta/tests.py b/tests/contribute_to_meta/tests.py
new file mode 100644
index 0000000000..6613588a4b
--- /dev/null
+++ b/tests/contribute_to_meta/tests.py
@@ -0,0 +1,49 @@
+from pathlib import Path
+
+from django.core.management import call_command
+from django.db import IntegrityError
+from django.test import TestCase, skipUnlessDBFeature
+
+from .models import ModelA, ModelC
+
+
+@skipUnlessDBFeature("supports_table_check_constraints")
+class ConstraintsTests(TestCase):
+    """Check that the constraints allow valid values and reject invalid ones"""
+
+    def test_ModelA_constraint(self):
+        ModelA.objects.create(field="valid")
+        with self.assertRaises(IntegrityError):
+            ModelA.objects.create(field="invalid")
+
+    def test_ModelC_constraint(self):
+        ModelC.objects.create(field="valid")
+        with self.assertRaises(IntegrityError):
+            ModelC.objects.create(field="invalid")
+
+
+class ConstraintsMigrationsTests(TestCase):
+    """Check that migrations correctly generate the constraints"""
+
+    @classmethod
+    def setUpClass(cls):
+        super().setUpClass()
+        # Clean and recreate migration files for further inspection
+        init_file = Path(__file__).parent / "migrations" / "0001_initial.py"
+        init_file.unlink(missing_ok=True)
+        call_command("makemigrations", verbosity=0)
+        cls.migration_content = init_file.read_text()
+
+    def test_ModelA(self):
+        # check migration contents
+        self.assertTrue(
+            "test_constraint_modela" in self.migration_content,
+            "Could not find constraint `test_constraint_modela` in migration",
+        )
+
+    def test_ModelC(self):
+        # check migration contents
+        self.assertTrue(
+            "test_constraint_modelc" in self.migration_content,
+            "Could not find constraint `test_constraint_modelc` in migration",
+        )