flask/CHANGES.rst

.. currentmodule:: flask

Flask Changelog
===============


Version 1.0
-----------

unreleased

-   **Python 2.6 and 3.3 are no longer supported.** (`pallets/meta#24`_)
-   Bump minimum dependency versions to the latest stable versions:
    Werkzeug >= 0.14, Jinja >= 2.10, itsdangerous >= 0.24, Click >= 5.1.
    (`#2586`_)
-   Skip :meth:`app.run <Flask.run>` when a Flask application is run
    from the command line. This avoids some behavior that was confusing
    to debug.
-   Change the default for :data:`JSONIFY_PRETTYPRINT_REGULAR` to
    ``False``. :func:`~json.jsonify` returns a compact format by
    default, and an indented format in debug mode. (`#2193`_)
-   :meth:`Flask.__init__ <Flask>` accepts the ``host_matching``
    argument and sets it on :attr:`~Flask.url_map`. (`#1559`_)
-   :meth:`Flask.__init__ <Flask>` accepts the ``static_host`` argument
    and passes it as the ``host`` argument when defining the static
    route. (`#1559`_)
-   :func:`send_file` supports Unicode in ``attachment_filename``.
    (`#2223`_)
-   Pass ``_scheme`` argument from :func:`url_for` to
    :meth:`~Flask.handle_url_build_error`. (`#2017`_)
-   :meth:`~Flask.add_url_rule` accepts the
    ``provide_automatic_options`` argument to disable adding the
    ``OPTIONS`` method. (`#1489`_)
-   :class:`~views.MethodView` subclasses inherit method handlers from
    base classes. (`#1936`_)
-   Errors caused while opening the session at the beginning of the
    request are handled by the app's error handlers. (`#2254`_)
-   Blueprints gained :attr:`~Blueprint.json_encoder` and
    :attr:`~Blueprint.json_decoder` attributes to override the app's
    encoder and decoder. (`#1898`_)
-   :meth:`Flask.make_response` raises ``TypeError`` instead of
    ``ValueError`` for bad response types. The error messages have been
    improved to describe why the type is invalid. (`#2256`_)
-   Add ``routes`` CLI command to output routes registered on the
    application. (`#2259`_)
-   Show warning when session cookie domain is a bare hostname or an IP
    address, as these may not behave properly in some browsers, such as
    Chrome. (`#2282`_)
-   Allow IP address as exact session cookie domain. (`#2282`_)
-   ``SESSION_COOKIE_DOMAIN`` is set if it is detected through
    ``SERVER_NAME``. (`#2282`_)
-   Auto-detect zero-argument app factory called ``create_app`` or
    ``make_app`` from ``FLASK_APP``. (`#2297`_)
-   Factory functions are not required to take a ``script_info``
    parameter to work with the ``flask`` command. If they take a single
    parameter or a parameter named ``script_info``, the
    :class:`~cli.ScriptInfo` object will be passed. (`#2319`_)
-   ``FLASK_APP`` can be set to an app factory, with arguments if
    needed, for example ``FLASK_APP=myproject.app:create_app('dev')``.
    (`#2326`_)
-   ``FLASK_APP`` can point to local packages that are not installed in
    editable mode, although ``pip install -e`` is still preferred.
    (`#2414`_)
-   The :class:`~views.View` class attribute
    :attr:`~views.View.provide_automatic_options` is set in
    :meth:`~views.View.as_view`, to be detected by
    :meth:`~Flask.add_url_rule`. (`#2316`_)
-   Error handling will try handlers registered for ``blueprint, code``,
    ``app, code``, ``blueprint, exception``, ``app, exception``.
    (`#2314`_)
-   ``Cookie`` is added to the response's ``Vary`` header if the session
    is accessed at all during the request (and not deleted). (`#2288`_)
-   :meth:`~Flask.test_request_context` accepts ``subdomain`` and
    ``url_scheme`` arguments for use when building the base URL.
    (`#1621`_)
-   Set :data:`APPLICATION_ROOT` to ``'/'`` by default. This was already
    the implicit default when it was set to ``None``.
-   :data:`TRAP_BAD_REQUEST_ERRORS` is enabled by default in debug mode.
    ``BadRequestKeyError`` has a message with the bad key in debug mode
    instead of the generic bad request message. (`#2348`_)
-   Allow registering new tags with
    :class:`~json.tag.TaggedJSONSerializer` to support storing other
    types in the session cookie. (`#2352`_)
-   Only open the session if the request has not been pushed onto the
    context stack yet. This allows :func:`~stream_with_context`
    generators to access the same session that the containing view uses.
    (`#2354`_)
-   Add ``json`` keyword argument for the test client request methods.
    This will dump the given object as JSON and set the appropriate
    content type. (`#2358`_)
-   Extract JSON handling to a mixin applied to both the
    :class:`Request` and :class:`Response` classes. This adds the
    :meth:`~Response.is_json` and :meth:`~Response.get_json` methods to
    the response to make testing JSON response much easier. (`#2358`_)
-   Removed error handler caching because it caused unexpected results
    for some exception inheritance hierarchies. Register handlers
    explicitly for each exception if you want to avoid traversing the
    MRO. (`#2362`_)
-   Fix incorrect JSON encoding of aware, non-UTC datetimes. (`#2374`_)
-   Template auto reloading will honor debug mode even even if
    :attr:`~Flask.jinja_env` was already accessed. (`#2373`_)
-   The following old deprecated code was removed. (`#2385`_)

    -   ``flask.ext`` - import extensions directly by their name instead
        of through the ``flask.ext`` namespace. For example,
        ``import flask.ext.sqlalchemy`` becomes
        ``import flask_sqlalchemy``.
    -   ``Flask.init_jinja_globals`` - extend
        :meth:`Flask.create_jinja_environment` instead.
    -   ``Flask.error_handlers`` - tracked by
        :attr:`Flask.error_handler_spec`, use :meth:`Flask.errorhandler`
        to register handlers.
    -   ``Flask.request_globals_class`` - use
        :attr:`Flask.app_ctx_globals_class` instead.
    -   ``Flask.static_path`` - use :attr:`Flask.static_url_path`
        instead.
    -   ``Request.module`` - use :attr:`Request.blueprint` instead.

-   The :attr:`Request.json` property is no longer deprecated.
    (`#1421`_)
-   Support passing a :class:`~werkzeug.test.EnvironBuilder` or
    ``dict`` to :meth:`test_client.open <werkzeug.test.Client.open>`.
    (`#2412`_)
-   The ``flask`` command and :meth:`Flask.run` will load environment
    variables from ``.env`` and ``.flaskenv`` files if python-dotenv is
    installed. (`#2416`_)
-   When passing a full URL to the test client, the scheme in the URL is
    used instead of :data:`PREFERRED_URL_SCHEME`. (`#2430`_)
-   :attr:`Flask.logger` has been simplified. ``LOGGER_NAME`` and
    ``LOGGER_HANDLER_POLICY`` config was removed. The logger is always
    named ``flask.app``. The level is only set on first access, it
    doesn't check :attr:`Flask.debug` each time. Only one format is
    used, not different ones depending on :attr:`Flask.debug`. No
    handlers are removed, and a handler is only added if no handlers are
    already configured. (`#2436`_)
-   Blueprint view function names may not contain dots. (`#2450`_)
-   Fix a ``ValueError`` caused by invalid ``Range`` requests in some
    cases. (`#2526`_)
-   The development server uses threads by default. (`#2529`_)
-   Loading config files with ``silent=True`` will ignore
    :data:`~errno.ENOTDIR` errors. (`#2581`_)
-   Pass ``--cert`` and ``--key`` options to ``flask run`` to run the
    development server over HTTPS. (`#2606`_)
-   Added :data:`SESSION_COOKIE_SAMESITE` to control the ``SameSite``
    attribute on the session cookie. (`#2607`_)
-   Added :meth:`~flask.Flask.test_cli_runner` to create a Click runner
    that can invoke Flask CLI commands for testing. (`#2636`_)
-   Subdomain matching is disabled by default and setting
    :data:`SERVER_NAME` does not implicily enable it. It can be enabled
    by passing ``subdomain_matching=True`` to the ``Flask`` constructor.
    (`#2635`_)
-   A single trailing slash is stripped from the blueprint
    ``url_prefix`` when it is registered with the app. (`#2629`_)
-   :meth:`Request.get_json` doesn't cache the
    result if parsing fails when ``silent`` is true. (`#2651`_)
-   :func:`Request.get_json` no longer accepts arbitrary encodings.
    Incoming JSON should be encoded using UTF-8 per :rfc:`8259`, but
    Flask will autodetect UTF-8, -16, or -32. (`#2691`_)
-   Added :data:`MAX_COOKIE_SIZE` and :attr:`Response.max_cookie_size`
    to control when Werkzeug warns about large cookies that browsers may
    ignore. (`#2693`_)
-   Updated documentation theme to make docs look better in small
    windows. (`#2709`_)
-   Rewrote the tutorial docs and example project to take a more
    structured approach to help new users avoid common pitfalls.
    (`#2676`_)

.. _pallets/meta#24: https://github.com/pallets/meta/issues/24
.. _#1421: https://github.com/pallets/flask/issues/1421
.. _#1489: https://github.com/pallets/flask/pull/1489
.. _#1559: https://github.com/pallets/flask/issues/1559
.. _#1621: https://github.com/pallets/flask/pull/1621
.. _#1898: https://github.com/pallets/flask/pull/1898
.. _#1936: https://github.com/pallets/flask/pull/1936
.. _#2017: https://github.com/pallets/flask/pull/2017
.. _#2193: https://github.com/pallets/flask/pull/2193
.. _#2223: https://github.com/pallets/flask/pull/2223
.. _#2254: https://github.com/pallets/flask/pull/2254
.. _#2256: https://github.com/pallets/flask/pull/2256
.. _#2259: https://github.com/pallets/flask/pull/2259
.. _#2282: https://github.com/pallets/flask/pull/2282
.. _#2288: https://github.com/pallets/flask/pull/2288
.. _#2297: https://github.com/pallets/flask/pull/2297
.. _#2314: https://github.com/pallets/flask/pull/2314
.. _#2316: https://github.com/pallets/flask/pull/2316
.. _#2319: https://github.com/pallets/flask/pull/2319
.. _#2326: https://github.com/pallets/flask/pull/2326
.. _#2348: https://github.com/pallets/flask/pull/2348
.. _#2352: https://github.com/pallets/flask/pull/2352
.. _#2354: https://github.com/pallets/flask/pull/2354
.. _#2358: https://github.com/pallets/flask/pull/2358
.. _#2362: https://github.com/pallets/flask/pull/2362
.. _#2374: https://github.com/pallets/flask/pull/2374
.. _#2373: https://github.com/pallets/flask/pull/2373
.. _#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
.. _#2430: https://github.com/pallets/flask/pull/2430
.. _#2436: https://github.com/pallets/flask/pull/2436
.. _#2450: https://github.com/pallets/flask/pull/2450
.. _#2526: https://github.com/pallets/flask/issues/2526
.. _#2529: https://github.com/pallets/flask/pull/2529
.. _#2586: https://github.com/pallets/flask/issues/2586
.. _#2581: https://github.com/pallets/flask/pull/2581
.. _#2606: https://github.com/pallets/flask/pull/2606
.. _#2607: https://github.com/pallets/flask/pull/2607
.. _#2636: https://github.com/pallets/flask/pull/2636
.. _#2635: https://github.com/pallets/flask/pull/2635
.. _#2629: https://github.com/pallets/flask/pull/2629
.. _#2651: https://github.com/pallets/flask/issues/2651
.. _#2676: https://github.com/pallets/flask/pull/2676
.. _#2691: https://github.com/pallets/flask/pull/2691
.. _#2693: https://github.com/pallets/flask/pull/2693
.. _#2709: https://github.com/pallets/flask/pull/2709


Version 0.12.2
--------------

Released on May 16 2017

- Fix a bug in `safe_join` on Windows.

Version 0.12.1
--------------

Bugfix release, released on March 31st 2017

- Prevent `flask run` from showing a NoAppException when an ImportError occurs
  within the imported application module.
- Fix encoding behavior of ``app.config.from_pyfile`` for Python 3. Fix
  ``#2118``.
- Use the ``SERVER_NAME`` config if it is present as default values for
  ``app.run``. ``#2109``, ``#2152``
- Call `ctx.auto_pop` with the exception object instead of `None`, in the
  event that a `BaseException` such as `KeyboardInterrupt` is raised in a
  request handler.

Version 0.12
------------

Released on December 21st 2016, codename Punsch.

- the cli command now responds to `--version`.
- Mimetype guessing and ETag generation for file-like objects in ``send_file``
  has been removed, as per issue ``#104``.  See pull request ``#1849``.
- Mimetype guessing in ``send_file`` now fails loudly and doesn't fall back to
  ``application/octet-stream``. See pull request ``#1988``.
- Make ``flask.safe_join`` able to join multiple paths like ``os.path.join``
  (pull request ``#1730``).
- Revert a behavior change that made the dev server crash instead of returning
  a Internal Server Error (pull request ``#2006``).
- Correctly invoke response handlers for both regular request dispatching as
  well as error handlers.
- Disable logger propagation by default for the app logger.
- Add support for range requests in ``send_file``.
- ``app.test_client`` includes preset default environment, which can now be
  directly set, instead of per ``client.get``.

Version 0.11.2
--------------

Bugfix release, unreleased

- Fix crash when running under PyPy3, see pull request ``#1814``.

Version 0.11.1
--------------

Bugfix release, released on June 7th 2016.

- Fixed a bug that prevented ``FLASK_APP=foobar/__init__.py`` from working. See
  pull request ``#1872``.

Version 0.11
------------

Released on May 29th 2016, codename Absinthe.

- Added support to serializing top-level arrays to :func:`flask.jsonify`. This
  introduces a security risk in ancient browsers. See
  :ref:`json-security` for details.
- Added before_render_template signal.
- Added `**kwargs` to :meth:`flask.Test.test_client` to support passing
  additional keyword arguments to the constructor of
  :attr:`flask.Flask.test_client_class`.
- Added ``SESSION_REFRESH_EACH_REQUEST`` config key that controls the
  set-cookie behavior.  If set to ``True`` a permanent session will be
  refreshed each request and get their lifetime extended, if set to
  ``False`` it will only be modified if the session actually modifies.
  Non permanent sessions are not affected by this and will always
  expire if the browser window closes.
- Made Flask support custom JSON mimetypes for incoming data.
- Added support for returning tuples in the form ``(response, headers)``
  from a view function.
- Added :meth:`flask.Config.from_json`.
- Added :attr:`flask.Flask.config_class`.
- Added :meth:`flask.Config.get_namespace`.
- Templates are no longer automatically reloaded outside of debug mode. This
  can be configured with the new ``TEMPLATES_AUTO_RELOAD`` config key.
- Added a workaround for a limitation in Python 3.3's namespace loader.
- Added support for explicit root paths when using Python 3.3's namespace
  packages.
- Added :command:`flask` and the ``flask.cli`` module to start the local
  debug server through the click CLI system.  This is recommended over the old
  ``flask.run()`` method as it works faster and more reliable due to a
  different design and also replaces ``Flask-Script``.
- Error handlers that match specific classes are now checked first,
  thereby allowing catching exceptions that are subclasses of HTTP
  exceptions (in ``werkzeug.exceptions``).  This makes it possible
  for an extension author to create exceptions that will by default
  result in the HTTP error of their choosing, but may be caught with
  a custom error handler if desired.
- Added :meth:`flask.Config.from_mapping`.
- Flask will now log by default even if debug is disabled.  The log format is
  now hardcoded but the default log handling can be disabled through the
  ``LOGGER_HANDLER_POLICY`` configuration key.
- Removed deprecated module functionality.
- Added the ``EXPLAIN_TEMPLATE_LOADING`` config flag which when enabled will
  instruct Flask to explain how it locates templates.  This should help
  users debug when the wrong templates are loaded.
- Enforce blueprint handling in the order they were registered for template
  loading.
- Ported test suite to py.test.
- Deprecated ``request.json`` in favour of ``request.get_json()``.
- Add "pretty" and "compressed" separators definitions in jsonify() method.
  Reduces JSON response size when JSONIFY_PRETTYPRINT_REGULAR=False by removing
  unnecessary white space included by default after separators.
- JSON responses are now terminated with a newline character, because it is a
  convention that UNIX text files end with a newline and some clients don't
  deal well when this newline is missing. See
  https://github.com/pallets/flask/pull/1262 -- this came up originally as a
  part of https://github.com/kennethreitz/httpbin/issues/168
- The automatically provided ``OPTIONS`` method is now correctly disabled if
  the user registered an overriding rule with the lowercase-version
  ``options`` (issue ``#1288``).
- ``flask.json.jsonify`` now supports the ``datetime.date`` type (pull request
  ``#1326``).
- Don't leak exception info of already catched exceptions to context teardown
  handlers (pull request ``#1393``).
- Allow custom Jinja environment subclasses (pull request ``#1422``).
- Updated extension dev guidelines.

- ``flask.g`` now has ``pop()`` and ``setdefault`` methods.
- Turn on autoescape for ``flask.templating.render_template_string`` by default
  (pull request ``#1515``).
- ``flask.ext`` is now deprecated (pull request ``#1484``).
- ``send_from_directory`` now raises BadRequest if the filename is invalid on
  the server OS (pull request ``#1763``).
- Added the ``JSONIFY_MIMETYPE`` configuration variable (pull request ``#1728``).
- Exceptions during teardown handling will no longer leave bad application
  contexts lingering around.

Version 0.10.2
--------------

(bugfix release, release date to be announced)

- Fixed broken `test_appcontext_signals()` test case.
- Raise an :exc:`AttributeError` in :func:`flask.helpers.find_package` with a
  useful message explaining why it is raised when a PEP 302 import hook is used
  without an `is_package()` method.
- Fixed an issue causing exceptions raised before entering a request or app
  context to be passed to teardown handlers.
- Fixed an issue with query parameters getting removed from requests in
  the test client when absolute URLs were requested.
- Made `@before_first_request` into a decorator as intended.
- Fixed an etags bug when sending a file streams with a name.
- Fixed `send_from_directory` not expanding to the application root path
  correctly.
- Changed logic of before first request handlers to flip the flag after
  invoking.  This will allow some uses that are potentially dangerous but
  should probably be permitted.
- Fixed Python 3 bug when a handler from `app.url_build_error_handlers`
  reraises the `BuildError`.

Version 0.10.1
--------------

(bugfix release, released on June 14th 2013)

- Fixed an issue where ``|tojson`` was not quoting single quotes which
  made the filter not work properly in HTML attributes.  Now it's
  possible to use that filter in single quoted attributes.  This should
  make using that filter with angular.js easier.
- Added support for byte strings back to the session system.  This broke
  compatibility with the common case of people putting binary data for
  token verification into the session.
- Fixed an issue where registering the same method twice for the same endpoint
  would trigger an exception incorrectly.

Version 0.10
------------

Released on June 13th 2013, codename Limoncello.

- Changed default cookie serialization format from pickle to JSON to
  limit the impact an attacker can do if the secret key leaks.  See
  :ref:`upgrading-to-010` for more information.
- Added ``template_test`` methods in addition to the already existing
  ``template_filter`` method family.
- Added ``template_global`` methods in addition to the already existing
  ``template_filter`` method family.
- Set the content-length header for x-sendfile.
- ``tojson`` filter now does not escape script blocks in HTML5 parsers.
- ``tojson`` used in templates is now safe by default due.  This was
  allowed due to the different escaping behavior.
- Flask will now raise an error if you attempt to register a new function
  on an already used endpoint.
- Added wrapper module around simplejson and added default serialization
  of datetime objects.  This allows much easier customization of how
  JSON is handled by Flask or any Flask extension.
- Removed deprecated internal ``flask.session`` module alias.  Use
  ``flask.sessions`` instead to get the session module.  This is not to
  be confused with ``flask.session`` the session proxy.
- Templates can now be rendered without request context.  The behavior is
  slightly different as the ``request``, ``session`` and ``g`` objects
  will not be available and blueprint's context processors are not
  called.
- The config object is now available to the template as a real global and
  not through a context processor which makes it available even in imported
  templates by default.
- Added an option to generate non-ascii encoded JSON which should result
  in less bytes being transmitted over the network.  It's disabled by
  default to not cause confusion with existing libraries that might expect
  ``flask.json.dumps`` to return bytestrings by default.
- ``flask.g`` is now stored on the app context instead of the request
  context.
- ``flask.g`` now gained a ``get()`` method for not erroring out on non
  existing items.
- ``flask.g`` now can be used with the ``in`` operator to see what's defined
  and it now is iterable and will yield all attributes stored.
- ``flask.Flask.request_globals_class`` got renamed to
  ``flask.Flask.app_ctx_globals_class`` which is a better name to what it
  does since 0.10.
- `request`, `session` and `g` are now also added as proxies to the template
  context which makes them available in imported templates.  One has to be
  very careful with those though because usage outside of macros might
  cause caching.
- Flask will no longer invoke the wrong error handlers if a proxy
  exception is passed through.
- Added a workaround for chrome's cookies in localhost not working
  as intended with domain names.
- Changed logic for picking defaults for cookie values from sessions
  to work better with Google Chrome.
- Added `message_flashed` signal that simplifies flashing testing.
- Added support for copying of request contexts for better working with
  greenlets.
- Removed custom JSON HTTP exception subclasses.  If you were relying on them
  you can reintroduce them again yourself trivially.  Using them however is
  strongly discouraged as the interface was flawed.
- Python requirements changed: requiring Python 2.6 or 2.7 now to prepare
  for Python 3.3 port.
- Changed how the teardown system is informed about exceptions.  This is now
  more reliable in case something handles an exception halfway through
  the error handling process.
- Request context preservation in debug mode now keeps the exception
  information around which means that teardown handlers are able to
  distinguish error from success cases.
- Added the ``JSONIFY_PRETTYPRINT_REGULAR`` configuration variable.
- Flask now orders JSON keys by default to not trash HTTP caches due to
  different hash seeds between different workers.
- Added `appcontext_pushed` and `appcontext_popped` signals.
- The builtin run method now takes the ``SERVER_NAME`` into account when
  picking the default port to run on.
- Added `flask.request.get_json()` as a replacement for the old
  `flask.request.json` property.

Version 0.9
-----------

Released on July 1st 2012, codename Campari.

- The :func:`flask.Request.on_json_loading_failed` now returns a JSON formatted
  response by default.
- The :func:`flask.url_for` function now can generate anchors to the
  generated links.
- The :func:`flask.url_for` function now can also explicitly generate
  URL rules specific to a given HTTP method.
- Logger now only returns the debug log setting if it was not set
  explicitly.
- Unregister a circular dependency between the WSGI environment and
  the request object when shutting down the request.  This means that
  environ ``werkzeug.request`` will be ``None`` after the response was
  returned to the WSGI server but has the advantage that the garbage
  collector is not needed on CPython to tear down the request unless
  the user created circular dependencies themselves.
- Session is now stored after callbacks so that if the session payload
  is stored in the session you can still modify it in an after
  request callback.
- The :class:`flask.Flask` class will avoid importing the provided import name
  if it can (the required first parameter), to benefit tools which build Flask
  instances programmatically.  The Flask class will fall back to using import
  on systems with custom module hooks, e.g. Google App Engine, or when the
  import name is inside a zip archive (usually a .egg) prior to Python 2.7.
- Blueprints now have a decorator to add custom template filters application
  wide, :meth:`flask.Blueprint.app_template_filter`.
- The Flask and Blueprint classes now have a non-decorator method for adding
  custom template filters application wide,
  :meth:`flask.Flask.add_template_filter` and
  :meth:`flask.Blueprint.add_app_template_filter`.
- The :func:`flask.get_flashed_messages` function now allows rendering flashed
  message categories in separate blocks, through a ``category_filter``
  argument.
- The :meth:`flask.Flask.run` method now accepts ``None`` for `host` and `port`
  arguments, using default values when ``None``.  This allows for calling run
  using configuration values, e.g. ``app.run(app.config.get('MYHOST'),
  app.config.get('MYPORT'))``, with proper behavior whether or not a config
  file is provided.
- The :meth:`flask.render_template` method now accepts a either an iterable of
  template names or a single template name.  Previously, it only accepted a
  single template name.  On an iterable, the first template found is rendered.
- Added :meth:`flask.Flask.app_context` which works very similar to the
  request context but only provides access to the current application.  This
  also adds support for URL generation without an active request context.
- View functions can now return a tuple with the first instance being an
  instance of :class:`flask.Response`.  This allows for returning
  ``jsonify(error="error msg"), 400`` from a view function.
- :class:`~flask.Flask` and :class:`~flask.Blueprint` now provide a
  :meth:`~flask.Flask.get_send_file_max_age` hook for subclasses to override
  behavior of serving static files from Flask when using
  :meth:`flask.Flask.send_static_file` (used for the default static file
  handler) and :func:`~flask.helpers.send_file`.  This hook is provided a
  filename, which for example allows changing cache controls by file extension.
  The default max-age for `send_file` and static files can be configured
  through a new ``SEND_FILE_MAX_AGE_DEFAULT`` configuration variable, which is
  used in the default `get_send_file_max_age` implementation.
- Fixed an assumption in sessions implementation which could break message
  flashing on sessions implementations which use external storage.
- Changed the behavior of tuple return values from functions.  They are no
  longer arguments to the response object, they now have a defined meaning.
- Added :attr:`flask.Flask.request_globals_class` to allow a specific class to
  be used on creation of the :data:`~flask.g` instance of each request.
- Added `required_methods` attribute to view functions to force-add methods
  on registration.
- Added :func:`flask.after_this_request`.
- Added :func:`flask.stream_with_context` and the ability to push contexts
  multiple times without producing unexpected behavior.

Version 0.8.1
-------------

Bugfix release, released on July 1st 2012

- Fixed an issue with the undocumented `flask.session` module to not
  work properly on Python 2.5.  It should not be used but did cause
  some problems for package managers.

Version 0.8
-----------

Released on September 29th 2011, codename Rakija

- Refactored session support into a session interface so that
  the implementation of the sessions can be changed without
  having to override the Flask class.
- Empty session cookies are now deleted properly automatically.
- View functions can now opt out of getting the automatic
  OPTIONS implementation.
- HTTP exceptions and Bad Request errors can now be trapped so that they
  show up normally in the traceback.
- Flask in debug mode is now detecting some common problems and tries to
  warn you about them.
- Flask in debug mode will now complain with an assertion error if a view
  was attached after the first request was handled.  This gives earlier
  feedback when users forget to import view code ahead of time.
- Added the ability to register callbacks that are only triggered once at
  the beginning of the first request. (:meth:`Flask.before_first_request`)
- Malformed JSON data will now trigger a bad request HTTP exception instead
  of a value error which usually would result in a 500 internal server
  error if not handled.  This is a backwards incompatible change.
- Applications now not only have a root path where the resources and modules
  are located but also an instance path which is the designated place to
  drop files that are modified at runtime (uploads etc.).  Also this is
  conceptually only instance depending and outside version control so it's
  the perfect place to put configuration files etc.  For more information
  see :ref:`instance-folders`.
- Added the ``APPLICATION_ROOT`` configuration variable.
- Implemented :meth:`~flask.testing.TestClient.session_transaction` to
  easily modify sessions from the test environment.
- Refactored test client internally.  The ``APPLICATION_ROOT`` configuration
  variable as well as ``SERVER_NAME`` are now properly used by the test client
  as defaults.
- Added :attr:`flask.views.View.decorators` to support simpler decorating of
  pluggable (class-based) views.
- Fixed an issue where the test client if used with the "with" statement did not
  trigger the execution of the teardown handlers.
- Added finer control over the session cookie parameters.
- HEAD requests to a method view now automatically dispatch to the `get`
  method if no handler was implemented.
- Implemented the virtual :mod:`flask.ext` package to import extensions from.
- The context preservation on exceptions is now an integral component of
  Flask itself and no longer of the test client.  This cleaned up some
  internal logic and lowers the odds of runaway request contexts in unittests.

Version 0.7.3
-------------

Bugfix release, release date to be decided

- Fixed the Jinja2 environment's list_templates method not returning the
  correct names when blueprints or modules were involved.

Version 0.7.2
-------------

Bugfix release, released on July 6th 2011

- Fixed an issue with URL processors not properly working on
  blueprints.

Version 0.7.1
-------------

Bugfix release, released on June 29th 2011

- Added missing future import that broke 2.5 compatibility.
- Fixed an infinite redirect issue with blueprints.

Version 0.7
-----------

Released on June 28th 2011, codename Grappa

- Added :meth:`~flask.Flask.make_default_options_response`
  which can be used by subclasses to alter the default
  behavior for ``OPTIONS`` responses.
- Unbound locals now raise a proper :exc:`RuntimeError` instead
  of an :exc:`AttributeError`.
- Mimetype guessing and etag support based on file objects is now
  deprecated for :func:`flask.send_file` because it was unreliable.
  Pass filenames instead or attach your own etags and provide a
  proper mimetype by hand.
- Static file handling for modules now requires the name of the
  static folder to be supplied explicitly.  The previous autodetection
  was not reliable and caused issues on Google's App Engine.  Until
  1.0 the old behavior will continue to work but issue dependency
  warnings.
- fixed a problem for Flask to run on jython.
- added a ``PROPAGATE_EXCEPTIONS`` configuration variable that can be
  used to flip the setting of exception propagation which previously
  was linked to ``DEBUG`` alone and is now linked to either ``DEBUG`` or
  ``TESTING``.
- Flask no longer internally depends on rules being added through the
  `add_url_rule` function and can now also accept regular werkzeug
  rules added to the url map.
- Added an `endpoint` method to the flask application object which
  allows one to register a callback to an arbitrary endpoint with
  a decorator.
- Use Last-Modified for static file sending instead of Date which
  was incorrectly introduced in 0.6.
- Added `create_jinja_loader` to override the loader creation process.
- Implemented a silent flag for `config.from_pyfile`.
- Added `teardown_request` decorator, for functions that should run at the end
  of a request regardless of whether an exception occurred.  Also the behavior
  for `after_request` was changed.  It's now no longer executed when an exception
  is raised.  See :ref:`upgrading-to-new-teardown-handling`
- Implemented :func:`flask.has_request_context`
- Deprecated `init_jinja_globals`.  Override the
  :meth:`~flask.Flask.create_jinja_environment` method instead to
  achieve the same functionality.
- Added :func:`flask.safe_join`
- The automatic JSON request data unpacking now looks at the charset
  mimetype parameter.
- Don't modify the session on :func:`flask.get_flashed_messages` if there
  are no messages in the session.
- `before_request` handlers are now able to abort requests with errors.
- it is not possible to define user exception handlers.  That way you can
  provide custom error messages from a central hub for certain errors that
  might occur during request processing (for instance database connection
  errors, timeouts from remote resources etc.).
- Blueprints can provide blueprint specific error handlers.
- Implemented generic :ref:`views` (class-based views).

Version 0.6.1
-------------

Bugfix release, released on December 31st 2010

- Fixed an issue where the default ``OPTIONS`` response was
  not exposing all valid methods in the ``Allow`` header.
- Jinja2 template loading syntax now allows "./" in front of
  a template load path.  Previously this caused issues with
  module setups.
- Fixed an issue where the subdomain setting for modules was
  ignored for the static folder.
- Fixed a security problem that allowed clients to download arbitrary files
  if the host server was a windows based operating system and the client
  uses backslashes to escape the directory the files where exposed from.

Version 0.6
-----------

Released on July 27th 2010, codename Whisky

- after request functions are now called in reverse order of
  registration.
- OPTIONS is now automatically implemented by Flask unless the
  application explicitly adds 'OPTIONS' as method to the URL rule.
  In this case no automatic OPTIONS handling kicks in.
- static rules are now even in place if there is no static folder
  for the module.  This was implemented to aid GAE which will
  remove the static folder if it's part of a mapping in the .yml
  file.
- the :attr:`~flask.Flask.config` is now available in the templates
  as `config`.
- context processors will no longer override values passed directly
  to the render function.
- added the ability to limit the incoming request data with the
  new ``MAX_CONTENT_LENGTH`` configuration value.
- the endpoint for the :meth:`flask.Module.add_url_rule` method
  is now optional to be consistent with the function of the
  same name on the application object.
- added a :func:`flask.make_response` function that simplifies
  creating response object instances in views.
- added signalling support based on blinker.  This feature is currently
  optional and supposed to be used by extensions and applications.  If
  you want to use it, make sure to have `blinker`_ installed.
- refactored the way URL adapters are created.  This process is now
  fully customizable with the :meth:`~flask.Flask.create_url_adapter`
  method.
- modules can now register for a subdomain instead of just an URL
  prefix.  This makes it possible to bind a whole module to a
  configurable subdomain.

.. _blinker: https://pypi.org/project/blinker/

Version 0.5.2
-------------

Bugfix Release, released on July 15th 2010

- fixed another issue with loading templates from directories when
  modules were used.

Version 0.5.1
-------------

Bugfix Release, released on July 6th 2010

- fixes an issue with template loading from directories when modules
  where used.

Version 0.5
-----------

Released on July 6th 2010, codename Calvados

- fixed a bug with subdomains that was caused by the inability to
  specify the server name.  The server name can now be set with
  the ``SERVER_NAME`` config key.  This key is now also used to set
  the session cookie cross-subdomain wide.
- autoescaping is no longer active for all templates.  Instead it
  is only active for ``.html``, ``.htm``, ``.xml`` and ``.xhtml``.
  Inside templates this behavior can be changed with the
  ``autoescape`` tag.
- refactored Flask internally.  It now consists of more than a
  single file.
- :func:`flask.send_file` now emits etags and has the ability to
  do conditional responses builtin.
- (temporarily) dropped support for zipped applications.  This was a
  rarely used feature and led to some confusing behavior.
- added support for per-package template and static-file directories.
- removed support for `create_jinja_loader` which is no longer used
  in 0.5 due to the improved module support.
- added a helper function to expose files from any directory.

Version 0.4
-----------

Released on June 18th 2010, codename Rakia

- added the ability to register application wide error handlers
  from modules.
- :meth:`~flask.Flask.after_request` handlers are now also invoked
  if the request dies with an exception and an error handling page
  kicks in.
- test client has not the ability to preserve the request context
  for a little longer.  This can also be used to trigger custom
  requests that do not pop the request stack for testing.
- because the Python standard library caches loggers, the name of
  the logger is configurable now to better support unittests.
- added ``TESTING`` switch that can activate unittesting helpers.
- the logger switches to ``DEBUG`` mode now if debug is enabled.

Version 0.3.1
-------------

Bugfix release, released on May 28th 2010

- fixed a error reporting bug with :meth:`flask.Config.from_envvar`
- removed some unused code from flask
- release does no longer include development leftover files (.git
  folder for themes, built documentation in zip and pdf file and
  some .pyc files)

Version 0.3
-----------

Released on May 28th 2010, codename Schnaps

- added support for categories for flashed messages.
- the application now configures a :class:`logging.Handler` and will
  log request handling exceptions to that logger when not in debug
  mode.  This makes it possible to receive mails on server errors
  for example.
- added support for context binding that does not require the use of
  the with statement for playing in the console.
- the request context is now available within the with statement making
  it possible to further push the request context or pop it.
- added support for configurations.

Version 0.2
-----------

Released on May 12th 2010, codename Jägermeister

- various bugfixes
- integrated JSON support
- added :func:`~flask.get_template_attribute` helper function.
- :meth:`~flask.Flask.add_url_rule` can now also register a
  view function.
- refactored internal request dispatching.
- server listens on 127.0.0.1 by default now to fix issues with chrome.
- added external URL support.
- added support for :func:`~flask.send_file`
- module support and internal request handling refactoring
  to better support pluggable applications.
- sessions can be set to be permanent now on a per-session basis.
- better error reporting on missing secret keys.
- added support for Google Appengine.

Version 0.1
-----------

First public preview release.