Convert Django test tags to Pytest markers

Django TestCase supports tags:
https://docs.djangoproject.com/en/4.2/topics/testing/tools/#topics-tagging-tests
These are basically similar to (basic) Pytest tags, so let's interpret
them to allow using the native pytest-native markers functionality.
This helps projects which are unable to convert tags to markers.

This may cause breakage for projects using `strict-markers`. Such
projects would need to add the tags to their `markers` config, or deal
with it some other way.

Fix #818.

pyproject.toml

@@ -18,6 +18,7 @@ addopts = [
 ]
 DJANGO_SETTINGS_MODULE = "pytest_django_test.settings_sqlite_file"
 testpaths = ["tests"]
+markers = ["tag1", "tag2", "tag3", "tag4", "tag5"]
 
 [tool.mypy]
 strict = true

pytest_django/plugin.py

@@ -377,6 +377,48 @@ def pytest_report_header(config: pytest.Config) -> Optional[List[str]]:
     return None
 
 
+# Convert Django test tags on test classes to pytest marks.
+def pytest_collectstart(collector: pytest.Collector) -> None:
+    if "django" not in sys.modules:
+        return
+
+    if not isinstance(collector, pytest.Class):
+        return
+
+    tags = getattr(collector.obj, "tags", ())
+    if not tags:
+        return
+
+    from django.test import TransactionTestCase
+
+    if not issubclass(collector.obj, TransactionTestCase):
+        return
+
+    for tag in tags:
+        collector.add_marker(tag)
+
+
+# Convert Django test tags on test methods to pytest marks.
+def pytest_itemcollected(item: pytest.Item) -> None:
+    if "django" not in sys.modules:
+        return
+
+    if not isinstance(item, pytest.Function):
+        return
+
+    tags = getattr(item.obj, "tags", ())
+    if not tags:
+        return
+
+    from django.test import TransactionTestCase
+
+    if not issubclass(item.cls, TransactionTestCase):
+        return
+
+    for tag in tags:
+        item.add_marker(tag)
+
+
 @pytest.hookimpl(tryfirst=True)
 def pytest_collection_modifyitems(items: List[pytest.Item]) -> None:
     # If Django is not configured we don't need to bother

tests/test_unittest.py

@@ -1,5 +1,5 @@
 import pytest
-from django.test import TestCase
+from django.test import TestCase, tag
 
 from .helpers import DjangoPytester
 
@@ -57,6 +57,41 @@ def tearDown(self) -> None:
         assert Item.objects.count() == 3
 
 
+@tag("tag1", "tag2")
+class TestDjangoTagsToPytestMarkers(TestCase):
+    """Django test tags are converted to Pytest markers, at the class & method
+    levels."""
+
+    @pytest.fixture(autouse=True)
+    def gimme_my_markers(self, request: pytest.FixtureRequest) -> None:
+        self.markers = {m.name for m in request.node.iter_markers()}
+
+    @tag("tag3", "tag4")  # type: ignore[misc]
+    def test_1(self) -> None:
+        assert self.markers == {"tag1", "tag2", "tag3", "tag4"}
+
+    def test_2(self) -> None:
+        assert self.markers == {"tag1", "tag2"}
+
+    @tag("tag5")  # type: ignore[misc]
+    def test_3(self) -> None:
+        assert self.markers == {"tag1", "tag2", "tag5"}
+
+
+@tag("tag1")
+class TestNonDjangoClassWithTags:
+    """Django test tags are only converted to Pytest markers if actually
+    Django tests. Use pytest markers directly for pytest tests."""
+
+    @pytest.fixture(autouse=True)
+    def gimme_my_markers(self, request: pytest.FixtureRequest) -> None:
+        self.markers = {m.name for m in request.node.iter_markers()}
+
+    @tag("tag2")  # type: ignore[misc]
+    def test_1(self) -> None:
+        assert not self.markers
+
+
 def test_sole_test(django_pytester: DjangoPytester) -> None:
     """
     Make sure the database is configured when only Django TestCase classes