Check if devserver overrides staticfiles runserver command

Ref: #100

Author: coagulant

README.rst

@@ -34,6 +34,11 @@ You will need to include ``devserver`` in your ``INSTALLED_APPS``::
 	    'devserver',            
 	)
 
+If you're using ``django.contrib.staticfiles`` or any other apps with management
+command ``runserver``, make sure to put ``devserver`` *above* any of them (or *below*,
+for ``Django<1.7``). Otherwise ``devserver`` will raise exception to ensure it is set up
+properly.
+
 -----
 Usage
 -----

devserver/models.py

@@ -1,11 +1,39 @@
+import django
 from django.core import exceptions
+from django.core.exceptions import ImproperlyConfigured
 
 from devserver.logger import GenericLogger
 
 
 MODULES = []
 
 
+def check_installed_apps_configuration():
+    """
+    Check the app is put in correct order in INSTALLED_APPS
+
+    django.contrib.staticfiles runserver command is likely to
+    override devserver management command if put in wrong order.
+
+    Django had reversed order of management commands collection prior to 1.7
+    https://code.djangoproject.com/ticket/16599
+    """
+    from django.conf import settings
+    try:
+        staticfiles_index = settings.INSTALLED_APPS.index('django.contrib.staticfiles')
+        devserver_index = settings.INSTALLED_APPS.index('devserver')
+    except ValueError:
+        pass
+    else:
+        latest_app_overrides = django.VERSION < (1, 7)
+        if devserver_index < staticfiles_index and latest_app_overrides:
+            raise ImproperlyConfigured(
+                'Put "devserver" below "django.contrib.staticfiles" in INSTALLED_APPS to make it work')
+        elif devserver_index > staticfiles_index and not latest_app_overrides:
+            raise ImproperlyConfigured(
+                'Put "devserver" above "django.contrib.staticfiles" in INSTALLED_APPS to make it work')
+
+
 def load_modules():
     global MODULES
 
@@ -37,4 +65,5 @@ def load_modules():
         MODULES.append(instance)
 
 if not MODULES:
+    check_installed_apps_configuration()
     load_modules()