rename to FLASK_SKIP_DOTENV, add docs, test

docs/cli.rst

@@ -201,6 +201,30 @@ These can be added to the ``.flaskenv`` file just like ``FLASK_APP`` to
 control default command options.
 
 
+Disable dotenv
+~~~~~~~~~~~~~~
+
+The ``flask`` command will show a message if it detects dotenv files but
+python-dotenv is not installed.
+
+.. code-block:: none
+
+    flask run
+     * Tip: There are .env files present. Do "pip install python-dotenv" to use them.
+
+You can tell Flask not to load dotenv files even when python-dotenv is
+installed by setting the ``FLASK_SKIP_DOTENV`` environment variable.
+This can be useful if you want to load them manually, or if you're using
+a project runner that loads them already. Keep in mind that the
+environment variables must be set before the app loads or it won't
+configure as expected.
+
+.. code-block:: none
+
+    export FLASK_SKIP_DOTENV=1
+    flask run
+
+
 Environment Variables From virtualenv
 -------------------------------------
 

flask/cli.py

@@ -28,7 +28,7 @@ from werkzeug.utils import import_string
 from . import __version__
 from ._compat import getargspec, iteritems, reraise, text_type
 from .globals import current_app
-from .helpers import get_debug_flag, get_env
+from .helpers import get_debug_flag, get_env, get_load_dotenv
 
 try:
     import dotenv
@@ -544,10 +544,7 @@ class FlaskGroup(AppGroup):
         # script that is loaded here also attempts to start a server.
         os.environ['FLASK_RUN_FROM_CLI'] = 'true'
 
-        val = os.environ.get('FLASK_DONT_LOAD_ENV')
-        load_dotenv =  not val or val in ('0', 'false', 'no')
-
-        if self.load_dotenv and load_dotenv:
+        if get_load_dotenv(self.load_dotenv):
             load_dotenv()
 
         obj = kwargs.get('obj')
@@ -586,12 +583,11 @@ def load_dotenv(path=None):
 
     .. versionadded:: 1.0
     """
-
     if dotenv is None:
         if path or os.path.exists('.env') or os.path.exists('.flaskenv'):
             click.secho(
                 ' * Tip: There are .env files present.'
-                ' Do "pip install python-dotenv" to use them',
+                ' Do "pip install python-dotenv" to use them.',
                 fg='yellow')
         return
 

flask/helpers.py

@@ -68,6 +68,21 @@ def get_debug_flag():
     return val.lower() not in ('0', 'false', 'no')
 
 
+def get_load_dotenv(default=True):
+    """Get whether the user has disabled loading dotenv files by setting
+    :envvar:`FLASK_SKIP_DOTENV`. The default is ``True``, load the
+    files.
+
+    :param default: What to return if the env var isn't set.
+    """
+    val = os.environ.get('FLASK_SKIP_DOTENV')
+
+    if not val:
+        return default
+
+    return val.lower() in ('0', 'false', 'no')
+
+
 def _endpoint_from_view_func(view_func):
     """Internal helper that returns the default endpoint for a given
     function.  This always is the function name.

tests/test_cli.py

@@ -474,6 +474,14 @@ def test_dotenv_optional(monkeypatch):
     assert 'FOO' not in os.environ
 
 
+@need_dotenv
+def test_disable_dotenv_from_env(monkeypatch, runner):
+    monkeypatch.chdir(test_path)
+    monkeypatch.setitem(os.environ, 'FLASK_SKIP_DOTENV', '1')
+    runner.invoke(FlaskGroup())
+    assert 'FOO' not in os.environ
+
+
 def test_run_cert_path():
     # no key
     with pytest.raises(click.BadParameter):