Show django settings in pytest output.

With the recent change to prefer DJANGO_SETTINGS_MODULE from the
environment rather than ini-file, it is nice to show which Django
settings is used and why it was choosen.

See discussion in pytest-dev/pytest-django#199
for more information.

pytest_django/plugin.py

@@ -194,9 +194,24 @@ def pytest_load_initial_conftests(early_config, parser, args):
         os.environ[INVALID_TEMPLATE_VARS_ENV] = 'true'
 
     # Configure DJANGO_SETTINGS_MODULE
-    ds = (options.ds or
-          os.environ.get(SETTINGS_MODULE_ENV) or
-          early_config.getini(SETTINGS_MODULE_ENV))
+
+    if options.ds:
+        ds_source = 'command line option'
+        ds = options.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)
+        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
 
     # Configure DJANGO_CONFIGURATION
     dc = (options.dc or
@@ -223,6 +238,11 @@ def pytest_load_initial_conftests(early_config, parser, args):
     _setup_django()
 
 
+def pytest_report_header(config):
+    if config._dsm_report_header:
+        return [config._dsm_report_header]
+
+
 @pytest.mark.trylast
 def pytest_configure():
     # Allow Django settings to be configured in a user pytest_configure call,

tests/test_django_settings_module.py

@@ -19,6 +19,26 @@
 '''
 
 
+def test_ds_ini(testdir, monkeypatch):
+    monkeypatch.delenv('DJANGO_SETTINGS_MODULE')
+    testdir.makeini("""
+       [pytest]
+       DJANGO_SETTINGS_MODULE = tpkg.settings_ini
+    """)
+    pkg = testdir.mkpydir('tpkg')
+    pkg.join('settings_ini.py').write(BARE_SETTINGS)
+    testdir.makepyfile("""
+        import os
+
+        def test_ds():
+            assert os.environ['DJANGO_SETTINGS_MODULE'] == 'tpkg.settings_ini'
+    """)
+    result = testdir.runpytest_subprocess()
+    assert result.parseoutcomes()['passed'] == 1
+    result.stdout.fnmatch_lines(['django settings: tpkg.settings_ini (from ini file)*'])
+    assert result.ret == 0
+
+
 def test_ds_env(testdir, monkeypatch):
     monkeypatch.setenv('DJANGO_SETTINGS_MODULE', 'tpkg.settings_env')
     pkg = testdir.mkpydir('tpkg')
@@ -31,48 +51,49 @@ def test_settings():
             assert os.environ['DJANGO_SETTINGS_MODULE'] == 'tpkg.settings_env'
     """)
     result = testdir.runpytest_subprocess()
-    result.stdout.fnmatch_lines(['*1 passed*'])
-    assert result.ret == 0
+    result.stdout.fnmatch_lines(['django settings: tpkg.settings_env (from '
+                                 'environment variable)*'])
+    assert result.parseoutcomes()['passed'] == 1
 
 
-def test_ds_ini(testdir, monkeypatch):
-    "DSM env should override ini."
-    monkeypatch.setenv('DJANGO_SETTINGS_MODULE', 'tpkg.settings_ini')
-    testdir.makeini("""\
+def test_ds_option(testdir, monkeypatch):
+    monkeypatch.setenv('DJANGO_SETTINGS_MODULE', 'DO_NOT_USE_env')
+    testdir.makeini("""
        [pytest]
        DJANGO_SETTINGS_MODULE = DO_NOT_USE_ini
     """)
     pkg = testdir.mkpydir('tpkg')
-    settings = pkg.join('settings_ini.py')
+    settings = pkg.join('settings_opt.py')
     settings.write(BARE_SETTINGS)
     testdir.makepyfile("""
         import os
 
         def test_ds():
-            assert os.environ['DJANGO_SETTINGS_MODULE'] == 'tpkg.settings_ini'
+            assert os.environ['DJANGO_SETTINGS_MODULE'] == 'tpkg.settings_opt'
     """)
-    result = testdir.runpytest_subprocess()
-    result.stdout.fnmatch_lines(['*1 passed*'])
-    assert result.ret == 0
+    result = testdir.runpytest_subprocess('--ds=tpkg.settings_opt')
+    result.stdout.fnmatch_lines(['django settings: tpkg.settings_opt (from command line option)'])
+    assert result.parseoutcomes()['passed'] == 1
 
 
-def test_ds_option(testdir, monkeypatch):
-    monkeypatch.setenv('DJANGO_SETTINGS_MODULE', 'DO_NOT_USE_env')
-    testdir.makeini("""
+def test_ds_env_override_ini(testdir, monkeypatch):
+    "DSM env should override ini."
+    monkeypatch.setenv('DJANGO_SETTINGS_MODULE', 'tpkg.settings_env')
+    testdir.makeini("""\
        [pytest]
        DJANGO_SETTINGS_MODULE = DO_NOT_USE_ini
     """)
     pkg = testdir.mkpydir('tpkg')
-    settings = pkg.join('settings_opt.py')
+    settings = pkg.join('settings_env.py')
     settings.write(BARE_SETTINGS)
     testdir.makepyfile("""
         import os
 
         def test_ds():
-            assert os.environ['DJANGO_SETTINGS_MODULE'] == 'tpkg.settings_opt'
+            assert os.environ['DJANGO_SETTINGS_MODULE'] == 'tpkg.settings_env'
     """)
-    result = testdir.runpytest_subprocess('--ds=tpkg.settings_opt')
-    result.stdout.fnmatch_lines(['*1 passed*'])
+    result = testdir.runpytest_subprocess()
+    assert result.parseoutcomes()['passed'] == 1
     assert result.ret == 0