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Provider hook to YAML Migration

We can now, redefine connection form metadata declaratively in provider.yaml of a provider instead of Python hook code, reducing dependencies and improving API server startup performance.

.. contents:: Table of Contents :depth: 2 :local:

Background

Previously, connection form UI metadata was defined in hook code of a provider using:

get_connection_form_widgets() - Custom form fields
get_ui_field_behaviour() - Field customizations (hidden, relabeling, placeholders)

These methods required importing heavy dependencies flask_appbuilder and wtforms, adding unnecessary dependencies to the API server and having API server to load all the provider hook code just to display a static form. The new yaml approach allows metadata to be loaded without importing hook classes.

YAML Schema Structure

Connection metadata is defined under connection-types in provider.yaml of a provider:

ui-field-behaviour


Customizations for standard connection fields:

.. code-block:: yaml

    ui-field-behaviour:
      hidden-fields:
        - schema
        - extra
      relabeling:
        host: Registry URL
        login: Username
      placeholders:
        port: '5432'

conn-fields
~~~~~~~~~~~

Custom fields which will be stored within ``Connection.extra``. The ``schema`` property uses
`JSON Schema <https://json-schema.org/>`_ to define field types and validation. For details on
supported field options, see
`Use Params to Provide a Trigger UI Form <https://airflow.apache.org/docs/apache-airflow/stable/core-concepts/params.html#use-params-to-provide-a-trigger-ui-form>`_.

.. code-block:: yaml

    conn-fields:
      keyfile_dict:
        label: "Keyfile JSON"
        description: "Service account JSON key"
        schema:
          type: string
          format: password
      project:
        label: "Project Id"
        schema:
          type: string
          default: "my-project"

Migration Tool
--------------

The ``generate_yaml_format_for_hooks.py`` script extracts metadata from existing Python hook code.
Use the airflow virtual environment to run the script.

Basic Usage
~~~~~~~~~~~

Extract from a provider:

.. code-block:: bash

    python scripts/generate_yaml_format_for_hooks.py --provider docker

Extract from a specific hook (some providers can have many hooks):

.. code-block:: bash

    python scripts/generate_yaml_format_for_hooks.py \
      --hook-class airflow.providers.docker.hooks.docker.DockerHook

Update provider.yaml directly:

.. code-block:: bash

    python scripts/generate_yaml_format_for_hooks.py --provider docker --update-yaml