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Flask v2.2.0 Release Notes

  • 🚀 Released 2022-08-01

    • 🚚 Remove previously deprecated code. :pr:4667

      • Old names for some send_file parameters have been removed. download_name replaces attachment_filename, max_age replaces cache_timeout, and etag replaces add_etags. Additionally, path replaces filename in send_from_directory.
      • The RequestContext.g property returning AppContext.g is removed.

    • ⚡️ Update Werkzeug dependency to >= 2.2.

    • The app and request contexts are managed using Python context vars directly rather than Werkzeug's LocalStack. This should result in better performance and memory use. :pr:4682

      • Extension maintainers, be aware that _app_ctx_stack.top and _request_ctx_stack.top are deprecated. Store data on g instead using a unique prefix, like g._extension_name_attr.

    • The FLASK_ENV environment variable and app.env attribute are deprecated, removing the distinction between development and debug mode. Debug mode should be controlled directly using the --debug option or app.run(debug=True). :issue:4714

    • 🗄 Some attributes that proxied config keys on app are deprecated: session_cookie_name, send_file_max_age_default, use_x_sendfile, propagate_exceptions, and templates_auto_reload. Use the relevant config keys instead. :issue:4716

    • Add new customization points to the Flask app object for many previously global behaviors.

      • flask.url_for will call app.url_for. :issue:4568
      • flask.abort will call app.aborter. Flask.aborter_class and Flask.make_aborter can be used to customize this aborter. :issue:4567
      • flask.redirect will call app.redirect. :issue:4569
      • flask.json is an instance of JSONProvider. A different provider can be set to use a different JSON library. flask.jsonify will call app.json.response, other functions in flask.json will call corresponding functions in app.json. :pr:4692

    • 🔧 JSON configuration is moved to attributes on the default app.json provider. JSON_AS_ASCII, JSON_SORT_KEYS, JSONIFY_MIMETYPE, and JSONIFY_PRETTYPRINT_REGULAR are deprecated. :pr:4692

    • Setting custom json_encoder and json_decoder classes on the app or a blueprint, and the corresponding json.JSONEncoder and JSONDecoder classes, are deprecated. JSON behavior can now be overridden using the app.json provider interface. :pr:4692

    • json.htmlsafe_dumps and json.htmlsafe_dump are deprecated, the function is built-in to Jinja now. :pr:4692

    • Refactor register_error_handler to consolidate error checking. Rewrite some error messages to be more consistent. :issue:4559

    • 🖨 Use Blueprint decorators and functions intended for setup after registering the blueprint will show a warning. In the next version, this will become an error just like the application setup methods. :issue:4571

    • before_first_request is deprecated. Run setup code when creating the application instead. :issue:4605

    • Added the View.init_every_request class attribute. If a view subclass sets this to False, the view will not create a new instance on every request. :issue:2520.

    • A flask.cli.FlaskGroup Click group can be nested as a sub-command in a custom CLI. :issue:3263

    • Add --app and --debug options to the flask CLI, instead of requiring that they are set through environment variables. :issue:2836

    • Add --env-file option to the flask CLI. This allows specifying a dotenv file to load in addition to .env and .flaskenv. :issue:3108

    • It is no longer required to decorate custom CLI commands on app.cli or blueprint.cli with @with_appcontext, an app context will already be active at that point. :issue:2410

    • SessionInterface.get_expiration_time uses a timezone-aware value. :pr:4645

    • View functions can return generators directly instead of wrapping them in a Response. :pr:4629

    • Add stream_template and stream_template_string functions to render a template as a stream of pieces. :pr:4629

    • A new implementation of context preservation during debugging and testing. :pr:4666

      • request, g, and other context-locals point to the correct data when running code in the interactive debugger console. :issue:2836
      • Teardown functions are always run at the end of the request, even if the context is preserved. They are also run after the preserved context is popped.
      • stream_with_context preserves context separately from a with client block. It will be cleaned up when response.get_data() or response.close() is called.

    • Allow returning a list from a view function, to convert it to a JSON response like a dict is. :issue:4672

    • When type checking, allow TypedDict to be returned from view functions. :pr:4695

    • 🚚 Remove the --eager-loading/--lazy-loading options from the flask run command. The app is always eager loaded the first time, then lazily loaded in the reloader. The reloader always prints errors immediately but continues serving. Remove the internal DispatchingApp middleware used by the previous implementation. :issue:4715