match run command behavior in app.run

output extra server information
handle env var changed by load_dotenv
enable threading by default

flask/app.py

@@ -864,9 +864,15 @@ class Flask(_PackageBoundObject):
             If installed, python-dotenv will be used to load environment
             variables from :file:`.env` and :file:`.flaskenv` files.
 
-        .. versionchanged:: 0.10
-           The default port is now picked from the ``SERVER_NAME`` variable.
+            If set, the :envvar:`FLASK_ENV` and :envvar:`FLASK_DEBUG`
+            environment variables will override :attr:`env` and
+            :attr:`debug`.
 
+            Threaded mode is enabled by default.
+
+        .. versionchanged:: 0.10
+            The default port is now picked from the ``SERVER_NAME``
+            variable.
         """
         # Change this into a no-op if the server is invoked from the
         # command line. Have a look at cli.py for more information.
@@ -876,9 +882,16 @@ class Flask(_PackageBoundObject):
             return
 
         if load_dotenv:
-            from flask.cli import load_dotenv
-            load_dotenv()
+            cli.load_dotenv()
 
+            # if set, let env vars override previous values
+            if 'FLASK_ENV' in os.environ:
+                self.env = get_env()
+                self.debug = get_debug_flag()
+            elif 'FLASK_DEBUG' in os.environ:
+                self.debug = get_debug_flag()
+
+        # debug passed to method overrides all other sources
         if debug is not None:
             self.debug = bool(debug)
 
@@ -892,8 +905,12 @@ class Flask(_PackageBoundObject):
 
         host = host or sn_host or _host
         port = int(port or sn_port or _port)
+
         options.setdefault('use_reloader', self.debug)
         options.setdefault('use_debugger', self.debug)
+        options.setdefault('threaded', True)
+
+        cli.show_server_banner(self.env, self.debug, self.name)
 
         from werkzeug.serving import run_simple
 

flask/cli.py

@@ -577,6 +577,28 @@ def load_dotenv(path=None):
     return new_dir is not None  # at least one file was located and loaded
 
 
+def show_server_banner(env, debug, app_import_path):
+    """Show extra startup messages the first time the server is run,
+    ignoring the reloader.
+    """
+    if os.environ.get('WERKZEUG_RUN_MAIN') == 'true':
+        return
+
+    if app_import_path is not None:
+        print(' * Serving Flask app "{0}"'.format(app_import_path))
+
+    print(' * Environment: {0}'.format(env))
+
+    if env == 'production':
+        click.secho(
+            '   WARNING: Do not use the development server in a production'
+            ' environment.', fg='red')
+        click.secho('   Use a production WSGI server instead.', dim=True)
+
+    if debug is not None:
+        print(' * Debug mode: {0}'.format('on' if debug else 'off'))
+
+
 @click.command('run', short_help='Runs a development server.')
 @click.option('--host', '-h', default='127.0.0.1',
               help='The interface to bind to.')
@@ -596,51 +618,31 @@ def load_dotenv(path=None):
 @pass_script_info
 def run_command(info, host, port, reload, debugger, eager_loading,
                 with_threads):
-    """Runs a local development server for the Flask application.
+    """Run a local development server.
 
-    This local server is recommended for development purposes only but it
-    can also be used for simple intranet deployments.  By default it will
-    not support any sort of concurrency at all to simplify debugging.  This
-    can be changed with the --with-threads option which will enable basic
-    multithreading.
+    This server is for development purposes only. It does not provide
+    the stability, security, or performance of production WSGI servers.
 
-    The reloader and debugger are by default enabled if the debug flag of
-    Flask is enabled and disabled otherwise.
+    The reloader and debugger are enabled by default if
+    FLASK_ENV=development or FLASK_DEBUG=1.
     """
-    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)
+        reload = debug
+
     if debugger is None:
-        debugger = bool(debug)
+        debugger = debug
+
     if eager_loading is None:
         eager_loading = not reload
 
+    show_server_banner(get_env(), debug, info.app_import_path)
     app = DispatchingApp(info.load_app, use_eager_loading=eager_loading)
 
-    # Extra startup messages.  This depends a bit on Werkzeug internals to
-    # not double execute when the reloader kicks in.
-    if os.environ.get('WERKZEUG_RUN_MAIN') != 'true':
-        # If we have an import path we can print it out now which can help
-        # people understand what's being served.  If we do not have an
-        # import path because the app was loaded through a callback then
-        # 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'))
-
-    run_simple(host, port, app, use_reloader=reload,
-               use_debugger=debugger, threaded=with_threads)
+    from werkzeug.serving import run_simple
+    run_simple(host, port, app, use_reloader=reload, use_debugger=debugger,
+               threaded=with_threads)
 
 
 @click.command('shell', short_help='Runs a shell in the app context.')