load env vars using python-dotenv

.gitignore

@@ -1,4 +1,6 @@
 .DS_Store
+.env
+.flaskenv
 *.pyc
 *.pyo
 env

.travis.yml

@@ -33,6 +33,11 @@ script:
 cache:
   - pip
 
+branches:
+  only:
+    - master
+    - /^.*-maintenance$/
+
 notifications:
   email: false
   irc:

CHANGES

@@ -101,6 +101,9 @@ Major release, unreleased
 - The ``request.json`` property is no longer deprecated. (`#1421`_)
 - Support passing an existing ``EnvironBuilder`` or ``dict`` to
   ``test_client.open``. (`#2412`_)
+- The ``flask`` command and ``app.run`` will load environment variables using
+  from ``.env`` and ``.flaskenv`` files if python-dotenv is installed.
+  (`#2416`_)
 
 .. _#1421: https://github.com/pallets/flask/issues/1421
 .. _#1489: https://github.com/pallets/flask/pull/1489
@@ -130,6 +133,7 @@ Major release, unreleased
 .. _#2385: https://github.com/pallets/flask/issues/2385
 .. _#2412: https://github.com/pallets/flask/pull/2412
 .. _#2414: https://github.com/pallets/flask/pull/2414
+.. _#2416: https://github.com/pallets/flask/pull/2416
 
 Version 0.12.2
 --------------

docs/api.rst

@@ -814,6 +814,8 @@ Command Line Interface
 .. autoclass:: ScriptInfo
    :members:
 
+.. autofunction:: load_dotenv
+
 .. autofunction:: with_appcontext
 
 .. autofunction:: pass_script_info

docs/cli.rst

@@ -97,9 +97,8 @@ Custom Commands
 ---------------
 
 If you want to add more commands to the shell script you can do this
-easily.  Flask uses `click`_ for the command interface which makes
-creating custom commands very easy.  For instance if you want a shell
-command to initialize the database you can do this::
+easily. For instance if you want a shell command to initialize the database you
+can do this::
 
     import click
     from flask import Flask
@@ -134,6 +133,35 @@ decorator::
     def example():
         pass
 
+
+.. _dotenv:
+
+Loading Environment Variables From ``.env`` Files
+-------------------------------------------------
+
+If `python-dotenv`_ is installed, running the :command:`flask` command will set
+environment variables defined in the files :file:`.env` and :file:`.flaskenv`.
+This can be used to avoid having to set ``FLASK_APP`` manually every time you
+open a new terminal, and to set configuration using environment variables
+similar to how some deployment services work.
+
+Variables set on the command line are used over those set in :file:`.env`,
+which are used over those set in :file:`.flaskenv`. :file:`.flaskenv` should be
+used for public variables, such as ``FLASK_APP``, while :file:`.env` should not
+be committed to your repository so that it can set private variables.
+
+Directories are scanned upwards from the directory you call :command:`flask`
+from to locate the files. The current working directory will be set to the
+location of the file, with the assumption that that is the top level project
+directory.
+
+The files are only loaded by the :command:`flask` command or calling
+:meth:`~flask.Flask.run`. If you would like to load these files when running in
+production, you should call :func:`~flask.cli.load_dotenv` manually.
+
+.. _python-dotenv: https://github.com/theskumar/python-dotenv#readme
+
+
 Factory Functions
 -----------------
 

docs/installation.rst

@@ -41,9 +41,12 @@ use them if you install them.
 * `SimpleJSON`_ is a fast JSON implementation that is compatible with
   Python's ``json`` module. It is preferred for JSON operations if it is
   installed.
+* `python-dotenv`_ enables support for :ref:`dotenv` when running ``flask``
+  commands.
 
 .. _Blinker: https://pythonhosted.org/blinker/
 .. _SimpleJSON: https://simplejson.readthedocs.io/
+.. _python-dotenv: https://github.com/theskumar/python-dotenv#readme
 
 Virtual environments
 --------------------

flask/app.py

@@ -820,7 +820,9 @@ class Flask(_PackageBoundObject):
         self.debug = debug
         self.jinja_env.auto_reload = self.templates_auto_reload
 
-    def run(self, host=None, port=None, debug=None, **options):
+    def run(
+        self, host=None, port=None, debug=None, 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
@@ -849,30 +851,40 @@ class Flask(_PackageBoundObject):
            won't catch any exceptions because there won't be any to
            catch.
 
-        .. versionchanged:: 0.10
-           The default port is now picked from the ``SERVER_NAME`` variable.
-
         :param host: the hostname to listen on. Set this to ``'0.0.0.0'`` to
             have the server available externally as well. Defaults to
-                     ``'127.0.0.1'`` or the host in the ``SERVER_NAME`` config
-                     variable if present.
+            ``'127.0.0.1'`` or the host in the ``SERVER_NAME`` config variable
+            if present.
         :param port: the port of the webserver. Defaults to ``5000`` or the
-                     port defined in the ``SERVER_NAME`` config variable if
-                     present.
-        :param debug: if given, enable or disable debug mode.
-                      See :attr:`debug`.
-        :param options: the options to be forwarded to the underlying
-                        Werkzeug server.  See
-                        :func:`werkzeug.serving.run_simple` for more
+            port defined in the ``SERVER_NAME`` config variable if present.
+        :param debug: if given, enable or disable debug mode. See
+            :attr:`debug`.
+        :param load_dotenv: Load the nearest :file:`.env` and :file:`.flaskenv`
+            files to set environment variables. Will also change the working
+            directory to the directory containing the first file found.
+        :param options: the options to be forwarded to the underlying Werkzeug
+            server. See :func:`werkzeug.serving.run_simple` for more
             information.
+
+        .. versionchanged:: 1.0
+            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.
+
         """
         # Change this into a no-op if the server is invoked from the
         # command line.  Have a look at cli.py for more information.
-        if os.environ.get('FLASK_RUN_FROM_CLI_SERVER') == '1':
+        if os.environ.get('FLASK_RUN_FROM_CLI') == 'true':
             from .debughelpers import explain_ignored_app_run
             explain_ignored_app_run()
             return
 
+        if load_dotenv:
+            from flask.cli import load_dotenv
+            load_dotenv()
+
         if debug is not None:
             self._reconfigure_for_run_debug(bool(debug))
 

flask/cli.py

@@ -8,6 +8,7 @@
     :copyright: (c) 2015 by Armin Ronacher.
     :license: BSD, see LICENSE for more details.
 """
+from __future__ import print_function
 
 import ast
 import inspect
@@ -22,10 +23,14 @@ from threading import Lock, Thread
 import click
 
 from . import __version__
-from ._compat import iteritems, reraise
+from ._compat import getargspec, iteritems, reraise
 from .globals import current_app
 from .helpers import get_debug_flag
-from ._compat import getargspec
+
+try:
+    import dotenv
+except ImportError:
+    dotenv = None
 
 
 class NoAppException(click.UsageError):
@@ -396,12 +401,21 @@ class FlaskGroup(AppGroup):
     :param add_default_commands: if this is True then the default run and
         shell commands wil be added.
     :param add_version_option: adds the ``--version`` option.
-    :param create_app: an optional callback that is passed the script info
-                       and returns the loaded app.
+    :param create_app: an optional callback that is passed the script info and
+        returns the loaded app.
+    :param load_dotenv: Load the nearest :file:`.env` and :file:`.flaskenv`
+        files to set environment variables. Will also change the working
+        directory to the directory containing the first file found.
+
+    .. versionchanged:: 1.0
+        If installed, python-dotenv will be used to load environment variables
+        from :file:`.env` and :file:`.flaskenv` files.
     """
 
-    def __init__(self, add_default_commands=True, create_app=None,
-                 add_version_option=True, **extra):
+    def __init__(
+        self, add_default_commands=True, create_app=None,
+        add_version_option=True, load_dotenv=True, **extra
+    ):
         params = list(extra.pop('params', None) or ())
 
         if add_version_option:
@@ -409,6 +423,7 @@ class FlaskGroup(AppGroup):
 
         AppGroup.__init__(self, params=params, **extra)
         self.create_app = create_app
+        self.load_dotenv = load_dotenv
 
         if add_default_commands:
             self.add_command(run_command)
@@ -472,12 +487,75 @@ class FlaskGroup(AppGroup):
         return sorted(rv)
 
     def main(self, *args, **kwargs):
+        # Set a global flag that indicates that we were invoked from the
+        # command line interface. This is detected by Flask.run to make the
+        # call into a no-op. This is necessary to avoid ugly errors when the
+        # script that is loaded here also attempts to start a server.
+        os.environ['FLASK_RUN_FROM_CLI'] = 'true'
+
+        if self.load_dotenv:
+            load_dotenv()
+
         obj = kwargs.get('obj')
+
         if obj is None:
             obj = ScriptInfo(create_app=self.create_app)
+
         kwargs['obj'] = obj
         kwargs.setdefault('auto_envvar_prefix', 'FLASK')
-        return AppGroup.main(self, *args, **kwargs)
+        return super(FlaskGroup, self).main(*args, **kwargs)
+
+
+def _path_is_ancestor(path, other):
+    """Take ``other`` and remove the length of ``path`` from it. Then join it
+    to ``path``. If it is the original value, ``path`` is an ancestor of
+    ``other``."""
+    return os.path.join(path, other[len(path):].lstrip(os.sep)) == other
+
+
+def load_dotenv(path=None):
+    """Load "dotenv" files in order of precedence to set environment variables.
+
+    If an env var is already set it is not overwritten, so earlier files in the
+    list are preferred over later files.
+
+    Changes the current working directory to the location of the first file
+    found, with the assumption that it is in the top level project directory
+    and will be where the Python path should import local packages from.
+
+    This is a no-op if `python-dotenv`_ is not installed.
+
+    .. _python-dotenv: https://github.com/theskumar/python-dotenv#readme
+
+    :param path: Load the file at this location instead of searching.
+    :return: ``True`` if a file was loaded.
+
+    .. versionadded:: 1.0
+    """
+
+    if dotenv is None:
+        return
+
+    if path is not None:
+        return dotenv.load_dotenv(path)
+
+    new_dir = None
+
+    for name in ('.env', '.flaskenv'):
+        path = dotenv.find_dotenv(name, usecwd=True)
+
+        if not path:
+            continue
+
+        if new_dir is None:
+            new_dir = os.path.dirname(path)
+
+        dotenv.load_dotenv(path)
+
+    if new_dir and os.getcwd() != new_dir:
+        os.chdir(new_dir)
+
+    return new_dir is not None  # at least one file was located and loaded
 
 
 @click.command('run', short_help='Runs a development server.')
@@ -512,13 +590,6 @@ def run_command(info, host, port, reload, debugger, eager_loading,
     """
     from werkzeug.serving import run_simple
 
-    # Set a global flag that indicates that we were invoked from the
-    # command line interface provided server command.  This is detected
-    # by Flask.run to make the call into a no-op.  This is necessary to
-    # avoid ugly errors when the script that is loaded here also attempts
-    # to start a server.
-    os.environ['FLASK_RUN_FROM_CLI_SERVER'] = '1'
-
     debug = get_debug_flag()
     if reload is None:
         reload = bool(debug)

setup.py

@@ -75,8 +75,10 @@ setup(
         'click>=4.0',
     ],
     extras_require={
+        'dotenv': ['python-dotenv'],
         'dev': [
             'blinker',
+            'python-dotenv',
             'greenlet',
             'pytest>=3',
             'coverage',

tests/test_apps/.env

@@ -0,0 +1,3 @@
+FOO=env
+SPAM=1
+EGGS=2

tests/test_apps/.flaskenv

@@ -0,0 +1,3 @@
+FOO=flaskenv
+BAR=bar
+EGGS=0

tests/test_cli.py

@@ -19,11 +19,31 @@ from functools import partial
 
 import click
 import pytest
+from _pytest.monkeypatch import notset
 from click.testing import CliRunner
 
 from flask import Flask, current_app
-from flask.cli import AppGroup, FlaskGroup, NoAppException, ScriptInfo, \
-    find_best_app, get_version, locate_app, prepare_import, with_appcontext
+from flask.cli import AppGroup, FlaskGroup, NoAppException, ScriptInfo, dotenv, \
+    find_best_app, get_version, load_dotenv, locate_app, prepare_import, \
+    with_appcontext
+
+cwd = os.getcwd()
+test_path = os.path.abspath(os.path.join(
+    os.path.dirname(__file__), 'test_apps'
+))
+
+
+@pytest.fixture(autouse=True)
+def manage_os_environ(monkeypatch):
+    # can't use monkeypatch.delitem since we don't want to restore a value
+    os.environ.pop('FLASK_APP', None)
+    os.environ.pop('FLASK_DEBUG', None)
+    # use monkeypatch internals to force-delete environ keys
+    monkeypatch._setitem.extend((
+        (os.environ, 'FLASK_APP', notset),
+        (os.environ, 'FLASK_DEBUG', notset),
+        (os.environ, 'FLASK_RUN_FROM_CLI', notset),
+    ))
 
 
 @pytest.fixture
@@ -125,12 +145,6 @@ def test_find_best_app(test_apps):
     pytest.raises(NoAppException, find_best_app, script_info, Module)
 
 
-cwd = os.getcwd()
-test_path = os.path.abspath(os.path.join(
-    os.path.dirname(__file__), 'test_apps'
-))
-
-
 @pytest.mark.parametrize('value,path,result', (
     ('test', cwd, 'test'),
     ('test.py', cwd, 'test'),
@@ -414,3 +428,46 @@ class TestRoutes:
         assert 'GET, HEAD, OPTIONS, POST' not in output
         output = invoke(['routes', '--all-methods']).output
         assert 'GET, HEAD, OPTIONS, POST' in output
+
+
+need_dotenv = pytest.mark.skipif(
+    dotenv is None, reason='dotenv is not installed'
+)
+
+
+@need_dotenv
+def test_load_dotenv(monkeypatch):
+    # can't use monkeypatch.delitem since the keys don't exist yet
+    for item in ('FOO', 'BAR', 'SPAM'):
+        monkeypatch._setitem.append((os.environ, item, notset))
+
+    monkeypatch.setenv('EGGS', '3')
+    monkeypatch.chdir(os.path.join(test_path, 'cliapp', 'inner1'))
+    load_dotenv()
+    assert os.getcwd() == test_path
+    # .flaskenv doesn't overwrite .env
+    assert os.environ['FOO'] == 'env'
+    # set only in .flaskenv
+    assert os.environ['BAR'] == 'bar'
+    # set only in .env
+    assert os.environ['SPAM'] == '1'
+    # set manually, files don't overwrite
+    assert os.environ['EGGS'] == '3'
+
+
+@need_dotenv
+def test_dotenv_path(monkeypatch):
+    for item in ('FOO', 'BAR', 'EGGS'):
+        monkeypatch._setitem.append((os.environ, item, notset))
+
+    cwd = os.getcwd()
+    load_dotenv(os.path.join(test_path, '.flaskenv'))
+    assert os.getcwd() == cwd
+    assert 'FOO' in os.environ
+
+
+def test_dotenv_optional(monkeypatch):
+    monkeypatch.setattr('flask.cli.dotenv', None)
+    monkeypatch.chdir(test_path)
+    load_dotenv()
+    assert 'FOO' not in os.environ

tox.ini

@@ -15,6 +15,7 @@ deps =
     coverage
     greenlet
     blinker
+    python-dotenv
 
     lowest: Werkzeug==0.9
     lowest: Jinja2==2.4
@@ -67,4 +68,4 @@ skip_install = true
 deps = detox
 commands =
     detox -e py{36,35,34,33,27,26,py},py{36,27,py}-simplejson,py{36,33,27,26,py}-devel,py{36,33,27,26,py}-lowest
-    tox -e coverage-report
+    tox -e docs-html,coverage-report