[WIP/RFC] Setup Django only later (pytest_configure)

pytest_django/plugin.py

@@ -4,7 +4,6 @@
 test database and provides some useful text fixtures.
 """
 
-import contextlib
 import inspect
 from functools import reduce
 import os
@@ -158,16 +157,7 @@ def pytest_addoption(parser):
     "projects since it is disabled in the configuration "
     '("django_find_project = false")'
 )
-
-
-@contextlib.contextmanager
-def _handle_import_error(extra_message):
-    try:
-        yield
-    except ImportError as e:
-        django_msg = (e.args[0] + "\n\n") if e.args else ""
-        msg = django_msg + extra_message
-        raise ImportError(msg)
+_django_project_scan_outcome = PROJECT_SCAN_DISABLED
 
 
 def _add_django_project_to_path(args):
@@ -262,88 +252,101 @@ def pytest_load_initial_conftests(early_config, parser, args):
         "variables (if --fail-on-template-vars is used).",
     )
 
-    options = parser.parse_known_args(args)
-
-    if options.version or options.help:
-        return
-
     django_find_project = _get_boolean_value(
         early_config.getini("django_find_project"), "django_find_project"
     )
-
     if django_find_project:
+        global _django_project_scan_outcome
         _django_project_scan_outcome = _add_django_project_to_path(args)
-    else:
-        _django_project_scan_outcome = PROJECT_SCAN_DISABLED
+
+
+def pytest_report_header(config):
+    if config._dsm_report_header:
+        return [config._dsm_report_header]
+
+
+@pytest.mark.trylast
+def pytest_configure(config):
+    if config.option.version or config.option.help:
+        return
+
+    # Allow Django settings to be configured in a user's pytest_configure, or
+    # conftest, but make sure we call django.setup().
 
     if (
-        options.itv
+        config.option.itv
         or _get_boolean_value(
             os.environ.get(INVALID_TEMPLATE_VARS_ENV), INVALID_TEMPLATE_VARS_ENV
         )
-        or early_config.getini(INVALID_TEMPLATE_VARS_ENV)
+        or config.getini(INVALID_TEMPLATE_VARS_ENV)
     ):
         os.environ[INVALID_TEMPLATE_VARS_ENV] = "true"
 
     # Configure DJANGO_SETTINGS_MODULE
-    if options.ds:
+    if config.option.ds:
         ds_source = "command line option"
-        ds = options.ds
+        ds = config.option.ds
     elif SETTINGS_MODULE_ENV in os.environ:
         ds = os.environ[SETTINGS_MODULE_ENV]
         ds_source = "environment variable"
-    elif early_config.getini(SETTINGS_MODULE_ENV):
-        ds = early_config.getini(SETTINGS_MODULE_ENV)
+    elif config.getini(SETTINGS_MODULE_ENV):
+        ds = config.getini(SETTINGS_MODULE_ENV)
         ds_source = "ini file"
     else:
         ds = None
         ds_source = None
 
-    if ds:
-        early_config._dsm_report_header = "Django settings: %s (from %s)" % (
-            ds,
-            ds_source,
-        )
-    else:
-        early_config._dsm_report_header = None
+    if not ds:
+        config._dsm_report_header = None
 
-    # Configure DJANGO_CONFIGURATION
-    dc = (
-        options.dc
-        or os.environ.get(CONFIGURATION_ENV)
-        or early_config.getini(CONFIGURATION_ENV)
-    )
-
-    if ds:
-        os.environ[SETTINGS_MODULE_ENV] = ds
-
-        if dc:
-            os.environ[CONFIGURATION_ENV] = dc
+        # Setup Django if settings are configured manually.
+        _setup_django()
 
-            # Install the django-configurations importer
-            import configurations.importer
+        return
 
-            configurations.importer.install()
+    config._dsm_report_header = "Django settings: %s (from %s)" % (
+        ds,
+        ds_source,
+    )
 
-        # Forcefully load Django settings, throws ImportError or
-        # ImproperlyConfigured if settings cannot be loaded.
-        from django.conf import settings as dj_settings
+    os.environ[SETTINGS_MODULE_ENV] = ds
 
-        with _handle_import_error(_django_project_scan_outcome):
-            dj_settings.DATABASES
+    # Configure DJANGO_CONFIGURATION
+    dc = (
+        config.option.dc
+        or os.environ.get(CONFIGURATION_ENV)
+        or config.getini(CONFIGURATION_ENV)
+    )
+    if dc:
+        os.environ[CONFIGURATION_ENV] = dc
 
-    _setup_django()
+        # Install the django-configurations importer
+        import configurations.importer
 
+        configurations.importer.install()
 
-def pytest_report_header(config):
-    if config._dsm_report_header:
-        return [config._dsm_report_header]
+    # Forcefully load Django settings.
+    # Throws ImportError or ImproperlyConfigured if settings cannot be loaded.
+    from django.conf import settings as dj_settings
 
+    try:
+        dj_settings.DATABASES
+    except ImportError as e:
+        django_msg = (e.args[0] + "\n\n") if e.args else ""
+        msg = django_msg + _django_project_scan_outcome
+
+        # Use UsageError here.
+        # - the traceback is not interesting, and raising the ImportError would
+        #   make pytest prefix it with INTERNALERROR even.
+        # - pytest.exit writes to both stdout and stderr?!
+        #
+        # The useful information from the header (_dsm_report_header) is not
+        # there in any case..
+        from _pytest.main import UsageError
+        raise UsageError(
+            "pytest-django could not setup Django due to ImportError: " + msg
+        )
 
-@pytest.mark.trylast
-def pytest_configure():
-    # Allow Django settings to be configured in a user pytest_configure call,
-    # but make sure we call django.setup()
     _setup_django()
 
 

tests/conftest.py

@@ -6,8 +6,6 @@
 import six
 from django.conf import settings
 
-from pytest_django_test.db_helpers import DB_NAME, TEST_DB_NAME
-
 try:
     import pathlib
 except ImportError:
@@ -40,6 +38,8 @@ def testdir(testdir, monkeypatch):
 
 @pytest.fixture(scope="function")
 def django_testdir(request, testdir, monkeypatch):
+    from pytest_django_test.db_helpers import DB_NAME, TEST_DB_NAME
+
     marker = request.node.get_closest_marker("django_project")
 
     options = _marker_apifun(**(marker.kwargs if marker else {}))

tests/test_database.py

@@ -274,8 +274,7 @@ def test_db_access_in_conftest(self, django_testdir):
         result = django_testdir.runpytest_subprocess("-v")
         result.stderr.fnmatch_lines(
             [
-                '*Failed: Database access not allowed, use the "django_db" mark, '
-                'or the "db" or "transactional_db" fixtures to enable it.*'
+                "E   django.core.exceptions.AppRegistryNotReady: Apps aren't loaded yet.",
             ]
         )
 

tests/test_initialization.py

@@ -1,24 +1,40 @@
 from textwrap import dedent
 
+import pytest
 
-def test_django_setup_order_and_uniqueness(django_testdir, monkeypatch):
+
+@pytest.mark.parametrize("conftest_mark", ("tryfirst", "trylast"))
+def test_django_setup_order_and_uniqueness(conftest_mark, django_testdir, monkeypatch):
     """
     The django.setup() function shall not be called multiple times by
     pytest-django, since it resets logging conf each time.
     """
     django_testdir.makeconftest(
         """
+        import pytest
         import django.apps
-        assert django.apps.apps.ready
-        from tpkg.app.models import Item
 
         print("conftest")
+
+        assert not django.apps.apps.ready
+
+        orig_django_setup = django.setup
+        def django_setup(*args, **kwargs):
+            print("django_setup")
+            orig_django_setup(*args, **kwargs)
+        django.setup = django_setup
+
+        @pytest.mark.{conftest_mark}
         def pytest_configure():
-            import django
+            if "{conftest_mark}" == "tryfirst":
+                assert not django.apps.apps.ready
+            else:
+                assert django.apps.apps.ready
+
             print("pytest_configure: conftest")
-            django.setup = lambda: SHOULD_NOT_GET_CALLED
-    """
-    )
+        """.format(
+            conftest_mark=conftest_mark
+        ))
 
     django_testdir.project_root.join("tpkg", "plugin.py").write(
         dedent(
@@ -29,13 +45,17 @@ def pytest_configure():
 
         print("plugin")
         def pytest_configure():
-            assert django.apps.apps.ready
-            from tpkg.app.models import Item
+            assert not django.apps.apps.ready
             print("pytest_configure: plugin")
 
-        @pytest.hookimpl(tryfirst=True)
+        @pytest.hookimpl(hookwrapper=True, tryfirst=True)
         def pytest_load_initial_conftests(early_config, parser, args):
-            print("pytest_load_initial_conftests")
+            print("pytest_load_initial_conftests_start")
+            assert not django.apps.apps.ready
+
+            yield
+
+            print("pytest_load_initial_conftests_end")
             assert not django.apps.apps.ready
     """
         )
@@ -47,14 +67,32 @@ def test_ds():
     """
     )
     result = django_testdir.runpytest_subprocess("-s", "-p", "tpkg.plugin")
-    result.stdout.fnmatch_lines(
-        [
-            "plugin",
-            "pytest_load_initial_conftests",
-            "conftest",
-            "pytest_configure: conftest",
-            "pytest_configure: plugin",
-            "*1 passed*",
-        ]
-    )
+
+    if conftest_mark == "tryfirst":
+        result.stdout.fnmatch_lines(
+            [
+                "plugin",
+                "pytest_load_initial_conftests_start",
+                "conftest",
+                "pytest_load_initial_conftests_end",
+                "pytest_configure: conftest",
+                "pytest_configure: plugin",
+                "django_setup",
+                "*1 passed*",
+            ]
+        )
+    else:
+        result.stdout.fnmatch_lines(
+            [
+                "plugin",
+                "pytest_load_initial_conftests_start",
+                "conftest",
+                "pytest_load_initial_conftests_end",
+                "pytest_configure: plugin",
+                "django_setup",
+                "pytest_configure: conftest",
+                "*1 passed*",
+            ]
+        )
+
     assert result.ret == 0