make DOTENV setting more robust

Add additional config options to DOTENV while retaining compatibility with the old way of setting it

configurations/base.py

@@ -95,6 +95,7 @@ def OTHER(self):
 
     """
     DOTENV_LOADED = None
+    DOTENV_RELOAD = False
 
     @classmethod
     def load_dotenv(cls):
@@ -109,6 +110,18 @@ def load_dotenv(cls):
         # check if the class has DOTENV set whether with a path or None
         dotenv = getattr(cls, 'DOTENV', None)
 
+        required = True
+        overwrite_env = False 
+        # check if the DOTENV is dict, and check all options of it
+        if isinstance(dotenv, dict):
+            # whether we want to overwrite previously set envs
+            overwrite_env = dotenv.get("overwrite", False)
+            # whether we want to error if the file is not found
+            required = dotenv.get("required", True)
+            # whether we want to reload on dotenv, useful if we want to frequently change it 
+            cls.DOTENV_RELOAD = dotenv.get("reload", False)
+            dotenv = dotenv.get("path", None)
+
         # if DOTENV is falsy we want to disable it
         if not dotenv:
             return
@@ -118,6 +131,8 @@ def load_dotenv(cls):
             with open(dotenv, 'r') as f:
                 content = f.read()
         except OSError as e:
+            if not required:
+                return
             raise ImproperlyConfigured("Couldn't read .env file "
                                        "with the path {}. Error: "
                                        "{}".format(dotenv, e)) from e
@@ -133,13 +148,16 @@ def load_dotenv(cls):
                 m3 = re.match(r'\A"(.*)"\Z', val)
                 if m3:
                     val = re.sub(r'\\(.)', r'\1', m3.group(1))
-                os.environ.setdefault(key, val)
+                if overwrite_env:
+                    os.environ[key] = val
+                else:
+                    os.environ.setdefault(key, val)
 
             cls.DOTENV_LOADED = dotenv
 
     @classmethod
     def pre_setup(cls):
-        if cls.DOTENV_LOADED is None:
+        if cls.DOTENV_LOADED is None or cls.DOTENV_RELOAD:
             cls.load_dotenv()
 
     @classmethod

docs/cookbook.rst

@@ -57,6 +57,20 @@ A ``.env`` file is a ``.ini``-style file. It must contain a list of
    API_KEY1=1234
    API_KEY2=5678
 
+``DOTENV`` can also be a dictionary, and then its behavior can be configured more:
+.. code-block:: python
+   BASE_DIR = os.path.dirname(os.path.dirname(__file__))
+
+   class Dev(Configuration):
+       DOTENV = {
+            "path": str(os.path.join(BASE_DIR, '.env')),
+            # if True, overwrites previously set environmental variables, if False only sets them if they haven't been set before 
+            "overwrite": True,
+            # if True errors if the DOTENV is not found at path, if False return
+            "required": False,
+            # if True, reloads DOTENV dynamically for example on hot reload
+            "reload": True,
+
 Envdir
 ------