Add Support for FLASK_ENV (#2570)

This introduces environments to Flask

docs/cli.rst

@@ -116,6 +116,16 @@ context will be active, and the app instance will be imported. ::
 
 Use :meth:`~Flask.shell_context_processor` to add other automatic imports.
 
+Environments
+------------
+
+.. versionadded:: 1.0
+
+The environment in which the Flask app should run is set by the
+:envvar:`FLASK_ENV` environment variable.  If not set it defaults to
+``production``.  The other default environment which is known is
+``development``.  If the env is set to ``development`` the debug mode is
+for instance automatically enabled.
 
 Debug Mode
 ----------
@@ -123,11 +133,14 @@ Debug Mode
 Set the :envvar:`FLASK_DEBUG` environment variable to override the
 application's :attr:`~Flask.debug` flag. The value ``1`` enables it, ``0``
 disables it. Forcing the debug flag on also enables the debugger and reloader
-when running the development server. ::
+when running the development server.
+
+::
 
     $ FLASK_DEBUG=1 flask run
      * Serving Flask app "hello"
      * Forcing debug mode on
+     * Env production
      * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
      * Restarting with inotify reloader
      * Debugger is active!

docs/config.rst

@@ -27,35 +27,52 @@ The :attr:`~flask.Flask.config` is actually a subclass of a dictionary and
 can be modified just like any dictionary::
 
     app = Flask(__name__)
-    app.config['DEBUG'] = True
+    app.config['TESTING'] = True
 
 Certain configuration values are also forwarded to the
 :attr:`~flask.Flask` object so you can read and write them from there::
 
-    app.debug = True
+    app.testing = True
 
 To update multiple keys at once you can use the :meth:`dict.update`
 method::
 
     app.config.update(
-        DEBUG=True,
+        TESTING=True,
         SECRET_KEY=b'_5#y2L"F4Q8z\n\xec]/'
     )
 
-.. admonition:: Debug Mode with the ``flask`` Script
+Environment and Debug Features
+------------------------------
 
-   If you use the :command:`flask` script to start a local development
+Some values are special in that they can show unexpected behavior when
-   server, to enable the debug mode, you need to export the ``FLASK_DEBUG``
+changed late.  In particular that applies to the Flask environment and
-   environment variable before running the server::
+debug mode.
 
-    $ export FLASK_DEBUG=1
+If you use the :command:`flask` script to start a local development server
-    $ flask run
+for instance you should tell Flask that you want to work in the
+development environment.  For safety reasons we default the flask
+environment to production mode instead of development.  This is done
+because development mode can turn on potentially unsafe features such as
+the debugger by default.
 
-   (On Windows you need to use ``set`` instead of ``export``).
+To control the environment and such fundamental features Flask provides
+the two environment variables :envvar:`FLASK_ENV` and :envvar:`FLASK_DEBUG`.
+In versions of Flask older than 1.0 the :envvar:`FLASK_ENV` environment
+variable did not exist.
 
-   ``app.debug`` and ``app.config['DEBUG']`` are not compatible with
+The most common way to switch Flask to development mode is to tell it to
-   the :command:`flask` script. They only worked when using ``Flask.run()``
+work on the ``development`` environment::
-   method.
+
+$ export FLASK_ENV=development
+$ flask run
+
+(On Windows you need to use ``set`` instead of ``export``).
+
+While you can attempt to flip the environment and debug flag separately in
+the Flask config from the config file this is strongly discouraged as
+those flags are often loaded early and changing them late might not apply
+to all systems and extensions.
 
 Builtin Configuration Values
 ----------------------------

docs/patterns/packages.rst

@@ -65,10 +65,10 @@ that tells Flask where to find the application instance::
     export FLASK_APP=yourapplication
 
 If you are outside of the project directory make sure to provide the exact 
-path to your application directory. Similarly you can turn on "debug 
+path to your application directory. Similarly you can turn on the
-mode" with this environment variable:: 
+development features like this::
 
-    export FLASK_DEBUG=true 
+    export FLASK_ENV=development
 
 In order to install and run the application you need to issue the following 
 commands::

docs/quickstart.rst

@@ -130,13 +130,16 @@ That is not very nice and Flask can do better.  If you enable debug
 support the server will reload itself on code changes, and it will also
 provide you with a helpful debugger if things go wrong.
 
-To enable debug mode you can export the ``FLASK_DEBUG`` environment variable
+To enable all development features (and to disable the debug mode) you can
+export the ``FLASK_ENV`` environment variable and set it to
+``development``
 before running the server::
 
-    $ export FLASK_DEBUG=1
+    $ export FLASK_ENV=development
     $ flask run
 
-(On Windows you need to use ``set`` instead of ``export``).
+(On Windows you need to use ``set`` instead of ``export`` and on Flask
+versions older than 1.0 you need to export ``FLASK_DEBUG=1`` instead).
 
 This does the following things:
 

docs/server.rst

@@ -12,12 +12,13 @@ but you can also continue using the :meth:`Flask.run` method.
 Command Line
 ------------
 
-The :command:`flask` command line script (:ref:`cli`) is strongly recommended for
+The :command:`flask` command line script (:ref:`cli`) is strongly
-development because it provides a superior reload experience due to how it
+recommended for development because it provides a superior reload
-loads the application.  The basic usage is like this::
+experience due to how it loads the application.  The basic usage is like
+this::
 
     $ export FLASK_APP=my_application
-    $ export FLASK_DEBUG=1
+    $ export FLASK_ENV=development
     $ flask run
 
 This will enable the debugger, the reloader and then start the server on
@@ -29,6 +30,13 @@ disabled::
 
     $ flask run --no-reload
 
+.. note::
+
+    On older Flask version (before 1.0) the :envvar:`FLASK_ENV`
+    environment variable is not supported and you need to enable the
+    debug mode separately by setting the :envvar:`FLASK_DEBUG` environment
+    variable to ``1``.
+
 In Code
 -------
 

docs/tutorial/packaging.rst

@@ -78,11 +78,13 @@ With that out of the way, you should be able to start up the application.
 Do this on Mac or Linux with the following commands in ``flaskr/``::
 
     export FLASK_APP=flaskr
-    export FLASK_DEBUG=true
+    export FLASK_ENV=development
     flask run
 
 (In case you are on Windows you need to use ``set`` instead of ``export``).
-The :envvar:`FLASK_DEBUG` flag enables or disables the interactive debugger.
+The :envvar:`FLASK_ENV` flag if set to ``development`` turns on all
+development features such as enabling the interactive debugger.
+
 *Never leave debug mode activated in a production system*, because it will
 allow users to execute code on the server!
 

flask/app.py

@@ -27,7 +27,7 @@ from .config import Config, ConfigAttribute
 from .ctx import AppContext, RequestContext, _AppCtxGlobals
 from .globals import _request_ctx_stack, g, request, session
 from .helpers import _PackageBoundObject, \
-    _endpoint_from_view_func, find_package, get_debug_flag, \
+    _endpoint_from_view_func, find_package, get_env, get_debug_flag, \
     get_flashed_messages, locked_cached_property, url_for
 from .logging import create_logger
 from .sessions import SecureCookieSessionInterface
@@ -196,15 +196,6 @@ class Flask(_PackageBoundObject):
     #: .. versionadded:: 0.11
     config_class = Config
 
-    #: The debug flag.  Set this to ``True`` to enable debugging of the
-    #: application.  In debug mode the debugger will kick in when an unhandled
-    #: exception occurs and the integrated server will automatically reload
-    #: the application if changes in the code are detected.
-    #:
-    #: This attribute can also be configured from the config with the ``DEBUG``
-    #: configuration key.  Defaults to ``False``.
-    debug = ConfigAttribute('DEBUG')
-
     #: The testing flag.  Set this to ``True`` to enable the test mode of
     #: Flask extensions (and in the future probably also Flask itself).
     #: For example this might activate test helpers that have an
@@ -278,7 +269,8 @@ class Flask(_PackageBoundObject):
 
     #: Default configuration parameters.
     default_config = ImmutableDict({
-        'DEBUG':                                get_debug_flag(default=False),
+        'ENV':                                  None,
+        'DEBUG':                                None,
         'TESTING':                              False,
         'PROPAGATE_EXCEPTIONS':                 None,
         'PRESERVE_CONTEXT_ON_EXCEPTION':        None,
@@ -647,7 +639,10 @@ class Flask(_PackageBoundObject):
         root_path = self.root_path
         if instance_relative:
             root_path = self.instance_path
-        return self.config_class(root_path, self.default_config)
+        defaults = dict(self.default_config)
+        defaults['ENV'] = get_env()
+        defaults['DEBUG'] = get_debug_flag()
+        return self.config_class(root_path, defaults)
 
     def auto_find_instance_path(self):
         """Tries to locate the instance path if it was not provided to the
@@ -790,25 +785,38 @@ class Flask(_PackageBoundObject):
             rv.update(processor())
         return rv
 
-    def _reconfigure_for_run_debug(self, debug):
+    #: The environment value.  This is typically set from outside the
-        """The ``run`` commands will set the application's debug flag. Some
+    #: process by setting the `FLASK_ENV` environment variable and can be
-        application configuration may already be calculated based on the
+    #: used to quickly switch between different environments like
-        previous debug value. This method will recalculate affected values.
+    #: `production` and `development`.  If not set this defaults to
+    #: `production`.
+    env = ConfigAttribute('ENV')
 
-        Called by the :func:`flask.cli.run` command or :meth:`Flask.run`
+    def _get_debug(self):
-        method if the debug flag is set explicitly in the call.
+        return self.config['DEBUG']
+    def _set_debug(self, value):
+        self._set_debug_value(value)
 
-        :param debug: the new value of the debug flag
+    #: The debug flag.  If this is ``True`` it enables debugging of the
+    #: application.  In debug mode the debugger will kick in when an
+    #: unhandled exception occurs and the integrated server will
+    #: automatically reload the application if changes in the code are
+    #: detected.
+    #:
+    #: This value should only be configured by the :envvar:`FLASK_DEBUG`
+    #: environment variable.  Changing it by other means will not yield
+    #: consistent results.  The default value depends on the Flask
+    #: environment and will be true for the development environment and false
+    #: otherwise.
+    debug = property(_get_debug, _set_debug)
+    del _get_debug, _set_debug
 
-        .. versionadded:: 1.0
+    def _set_debug_value(self, value):
-            Reconfigures ``app.jinja_env.auto_reload``.
+        self.config['DEBUG'] = value
-        """
-        self.debug = debug
         self.jinja_env.auto_reload = self.templates_auto_reload
 
-    def run(
+    def run(self, host=None, port=None, debug=None,
-        self, host=None, port=None, debug=None, load_dotenv=True, **options
+            load_dotenv=True, **options):
-    ):
         """Runs the application on a local development server.
 
         Do not use ``run()`` in a production setting. It is not intended to
@@ -872,11 +880,11 @@ class Flask(_PackageBoundObject):
             load_dotenv()
 
         if debug is not None:
-            self._reconfigure_for_run_debug(bool(debug))
+            self.debug = bool(debug)
 
         _host = '127.0.0.1'
         _port = 5000
-        server_name = self.config.get("SERVER_NAME")
+        server_name = self.config.get('SERVER_NAME')
         sn_host, sn_port = None, None
 
         if server_name:
@@ -1055,7 +1063,8 @@ class Flask(_PackageBoundObject):
         return iter(self._blueprint_order)
 
     @setupmethod
-    def add_url_rule(self, rule, endpoint=None, view_func=None, provide_automatic_options=None, **options):
+    def add_url_rule(self, rule, endpoint=None, view_func=None,
+                     provide_automatic_options=None, **options):
         """Connects a URL rule.  Works exactly like the :meth:`route`
         decorator.  If a view_func is provided it will be registered with the
         endpoint.

flask/cli.py

@@ -25,7 +25,7 @@ import click
 from . import __version__
 from ._compat import getargspec, iteritems, reraise
 from .globals import current_app
-from .helpers import get_debug_flag
+from .helpers import get_debug_flag, get_env
 
 try:
     import dotenv
@@ -341,9 +341,8 @@ class ScriptInfo(object):
             else:
                 for path in ('wsgi.py', 'app.py'):
                     import_name = prepare_import(path)
-                    app = locate_app(
+                    app = locate_app(self, import_name, None,
-                        self, import_name, None, raise_if_not_found=False
+                                     raise_if_not_found=False)
-                    )
 
                     if app:
                         break
@@ -357,8 +356,10 @@ class ScriptInfo(object):
 
         debug = get_debug_flag()
 
+        # Update the app's debug flag through the descriptor so that other
+        # values repopulate as well.
         if debug is not None:
-            app._reconfigure_for_run_debug(debug)
+            app.debug = debug
 
         self._loaded_app = app
         return app
@@ -432,10 +433,8 @@ class FlaskGroup(AppGroup):
         from :file:`.env` and :file:`.flaskenv` files.
     """
 
-    def __init__(
+    def __init__(self, add_default_commands=True, create_app=None,
-        self, add_default_commands=True, create_app=None,
+                 add_version_option=True, load_dotenv=True, **extra):
-        add_version_option=True, load_dotenv=True, **extra
-    ):
         params = list(extra.pop('params', None) or ())
 
         if add_version_option:
@@ -610,6 +609,13 @@ def run_command(info, host, port, reload, debugger, eager_loading,
     """
     from werkzeug.serving import run_simple
 
+    if get_env() == 'production':
+        click.secho('Warning: Detected a production environment. Do not '
+                    'use `flask run` for production use.',
+                    fg='red')
+        click.secho('Use a production ready WSGI server instead',
+                    dim=True)
+
     debug = get_debug_flag()
     if reload is None:
         reload = bool(debug)
@@ -629,6 +635,7 @@ def run_command(info, host, port, reload, debugger, eager_loading,
         # we won't print anything.
         if info.app_import_path is not None:
             print(' * Serving Flask app "%s"' % info.app_import_path)
+        print(' * Env %s' % get_env())
         if debug is not None:
             print(' * Forcing debug mode %s' % (debug and 'on' or 'off'))
 
@@ -649,11 +656,11 @@ def shell_command():
     import code
     from flask.globals import _app_ctx_stack
     app = _app_ctx_stack.top.app
-    banner = 'Python %s on %s\nApp: %s%s\nInstance: %s' % (
+    banner = 'Python %s on %s\nApp: %s [%s]\nInstance: %s' % (
         sys.version,
         sys.platform,
         app.import_name,
-        app.debug and ' [debug]' or '',
+        app.env,
         app.instance_path,
     )
     ctx = {}

flask/helpers.py

@@ -46,10 +46,20 @@ _os_alt_seps = list(sep for sep in [os.path.sep, os.path.altsep]
                     if sep not in (None, '/'))
 
 
-def get_debug_flag(default=None):
+def get_env():
+    val = os.environ.get('FLASK_ENV')
+    if not val:
+        val = 'production'
+    return val
+
+
+def get_debug_flag():
     val = os.environ.get('FLASK_DEBUG')
     if not val:
-        return default
+        env = get_env()
+        if env == 'development':
+            return True
+        return False
     return val.lower() not in ('0', 'false', 'no')
 
 

tests/test_helpers.py

@@ -21,7 +21,7 @@ from werkzeug.http import http_date, parse_cache_control_header, \
 
 import flask
 from flask._compat import StringIO, text_type
-from flask.helpers import get_debug_flag
+from flask.helpers import get_debug_flag, get_env
 
 
 def has_encoding(name):
@@ -886,7 +886,7 @@ class TestSafeJoin(object):
 class TestHelpers(object):
 
     @pytest.mark.parametrize('debug, expected_flag, expected_default_flag', [
-        ('', None, True),
+        ('', False, False),
         ('0', False, False),
         ('False', False, False),
         ('No', False, False),
@@ -898,7 +898,18 @@ class TestHelpers(object):
             assert get_debug_flag() is None
         else:
             assert get_debug_flag() == expected_flag
-        assert get_debug_flag(default=True) == expected_default_flag
+        assert get_debug_flag() == expected_default_flag
+
+    @pytest.mark.parametrize('env, ref_env, debug', [
+        ('', 'production', False),
+        ('production', 'production', False),
+        ('development', 'development', True),
+        ('other', 'other', False),
+    ])
+    def test_get_env(self, monkeypatch, env, ref_env, debug):
+        monkeypatch.setenv('FLASK_ENV', env)
+        assert get_debug_flag() == debug
+        assert get_env() == ref_env
 
     def test_make_response(self):
         app = flask.Flask(__name__)