.. _flask-framework-reference:

flask-framework
---------------

The Flask extension streamlines the process of building Flask application rocks.

It facilitates the installation of Flask application dependencies, including
Gunicorn, inside the rock. Additionally, it transfers your project files to
``/flask/app`` within the rock.

A statsd-exporter is installed alongside the Gunicorn server to export Gunicorn
server metrics.

.. note::
    The Flask extension is compatible with the ``bare`` and ``ubuntu@22.04``
    bases.

Project requirements
====================

There are 2 requirements to be able to use the ``flask-framework`` extension:

1. There must be a ``requirements.txt`` file in the root of the project with
   ``Flask`` declared as a dependency
2. The project must include a WSGI app with the path ``app:app``. This means
   there must be an ``app.py`` file at the root of the project with the name
   of the Flask object is set to ``app``

``parts`` > ``flask-framework/runtime-slices`` > ``stage-packages``
===================================================================

You can use this field to specify any :ref:`chisel_explanation` package slices
required for your Flask
application. For example, below we use it to specify ``libxml2_libs``:

.. code-block:: yaml

  parts:
    flask-framework/runtime-slices:
      stage-packages:
        # list required Chisel package slices for your flask application below.
        - libxml2_libs

``parts`` > ``flask-framework/runtime-debs`` > ``stage-packages``
=================================================================

You can use this field to specify any Debian packages required for your Flask
application. For example, below we use it to specify ``libpq-dev``:

.. code-block:: yaml

  parts:
    flask-framework/runtime-debs:
      stage-packages:
        # list required Debian packages for your flask application below.
        - libpq-dev

``parts`` > ``flask-framework/install-app`` > ``prime``
=======================================================

You can use this field to specify the files to be included or excluded from
your rock upon ``rockcraft pack``. Follow the ``flask/app/<filename>``
notation. For example:

.. code-block:: yaml

  parts:
    flask-framework/install-app:
      prime:
        - flask/app/.env
        - flask/app/app.py
        - flask/app/webapp
        - flask/app/templates
        - flask/app/static

Some files, if they exist, are included by default. These include:
``app``, ``app.py``, ``migrate``, ``migrate.sh``, ``migrate.py``, ``static``,
``templates``.

Useful links
============

- :ref:`build-a-rock-for-a-flask-application`