kopia lustrzana https://github.com/simonw/datasette
509 wiersze
16 KiB
ReStructuredText
509 wiersze
16 KiB
ReStructuredText
.. _plugins:
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Plugins
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=======
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Datasette's plugin system is currently under active development. It allows
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additional features to be implemented as Python code (or front-end JavaScript)
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which can be wrapped up in a separate Python package. The underlying mechanism
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uses `pluggy <https://pluggy.readthedocs.io/>`_.
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You can follow the development of plugins in `issue #14 <https://github.com/simonw/datasette/issues/14>`_.
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Using plugins
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-------------
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If a plugin has been packaged for distribution using setuptools you can use
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the plugin by installing it alongside Datasette in the same virtual
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environment or Docker container.
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You can also define one-off per-project plugins by saving them as
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``plugin_name.py`` functions in a ``plugins/`` folder and then passing that
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folder to ``datasette serve``.
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The ``datasette publish`` and ``datasette package`` commands both take an
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optional ``--install`` argument. You can use this one or more times to tell
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Datasette to ``pip install`` specific plugins as part of the process. You can
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use the name of a package on PyPI or any of the other valid arguments to ``pip
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install`` such as a URL to a ``.zip`` file::
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datasette publish now mydb.db \
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--install=datasette-plugin-demos \
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--install=https://url-to-my-package.zip
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Writing plugins
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---------------
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The easiest way to write a plugin is to create a ``my_plugin.py`` file and
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drop it into your ``plugins/`` directory. Here is an example plugin, which
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adds a new custom SQL function called ``hello_world()`` which takes no
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arguments and returns the string ``Hello world!``.
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.. code-block:: python
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from datasette import hookimpl
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@hookimpl
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def prepare_connection(conn):
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conn.create_function('hello_world', 0, lambda: 'Hello world!')
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If you save this in ``plugins/my_plugin.py`` you can then start Datasette like
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this::
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datasette serve mydb.db --plugins-dir=plugins/
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Now you can navigate to http://localhost:8001/mydb and run this SQL::
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select hello_world();
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To see the output of your plugin.
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Packaging a plugin
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------------------
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Plugins can be packaged using Python setuptools. You can see an example of a
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packaged plugin at https://github.com/simonw/datasette-plugin-demos
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The example consists of two files: a ``setup.py`` file that defines the plugin:
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.. code-block:: python
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from setuptools import setup
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VERSION = '0.1'
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setup(
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name='datasette-plugin-demos',
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description='Examples of plugins for Datasette',
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author='Simon Willison',
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url='https://github.com/simonw/datasette-plugin-demos',
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license='Apache License, Version 2.0',
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version=VERSION,
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py_modules=['datasette_plugin_demos'],
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entry_points={
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'datasette': [
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'plugin_demos = datasette_plugin_demos'
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]
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},
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install_requires=['datasette']
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)
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And a Python module file, ``datasette_plugin_demos.py``, that implements the
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plugin:
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.. code-block:: python
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from datasette import hookimpl
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import random
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@hookimpl
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def prepare_jinja2_environment(env):
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env.filters['uppercase'] = lambda u: u.upper()
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@hookimpl
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def prepare_connection(conn):
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conn.create_function('random_integer', 2, random.randint)
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Having built a plugin in this way you can turn it into an installable package
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using the following command::
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python3 setup.py sdist
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This will create a ``.tar.gz`` file in the ``dist/`` directory.
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You can then install your new plugin into a Datasette virtual environment or
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Docker container using ``pip``::
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pip install datasette-plugin-demos-0.1.tar.gz
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To learn how to upload your plugin to `PyPI <https://pypi.org/>`_ for use by
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other people, read the PyPA guide to `Packaging and distributing projects
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<https://packaging.python.org/tutorials/distributing-packages/>`_.
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Static assets
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-------------
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If your plugin has a ``static/`` directory, Datasette will automatically
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configure itself to serve those static assets from the following path::
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/-/static-plugins/NAME_OF_PLUGIN_PACKAGE/yourfile.js
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See `the datasette-plugin-demos repository <https://github.com/simonw/datasette-plugin-demos/tree/0ccf9e6189e923046047acd7878d1d19a2cccbb1>`_
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for an example of how to create a package that includes a static folder.
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Custom templates
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----------------
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If your plugin has a ``templates/`` directory, Datasette will attempt to load
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templates from that directory before it uses its own default templates.
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The priority order for template loading is:
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* templates from the ``--template-dir`` argument, if specified
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* templates from the ``templates/`` directory in any installed plugins
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* default templates that ship with Datasette
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See :ref:`customization` for more details on how to write custom templates,
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including which filenames to use to customize which parts of the Datasette UI.
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.. _plugins_configuration:
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Plugin configuration
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--------------------
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Plugins can have their own configuration, embedded in a :ref:`metadata` file. Configuration options for plugins live within a ``"plugins"`` key in that file, which can be included at the root, database or table level.
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Here is an example of some plugin configuration for a specific table::
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{
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"databases: {
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"sf-trees": {
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"tables": {
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"Street_Tree_List": {
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"plugins": {
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"datasette-cluster-map": {
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"latitude_column": "lat",
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"longitude_column": "lng"
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}
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}
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}
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}
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}
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}
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}
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This tells the ``datasette-cluster-map`` column which latitude and longitude columns should be used for a table called ``Street_Tree_List`` inside a database file called ``sf-trees.db``.
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When you are writing plugins, you can access plugin configuration like this using the ``datasette.plugin_config()`` method. If you know you need plugin configuration for a specific table, you can access it like this::
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plugin_config = datasette.plugin_config(
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"datasette-cluster-map", database="sf-trees", table="Street_Tree_List"
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)
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This will return the ``{"latitude_column": "lat", "longitude_column": "lng"}`` in the above example.
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If it cannot find the requested configuration at the table layer, it will fall back to the database layer and then the root layer. For example, a user may have set the plugin configuration option like so::
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{
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"databases: {
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"sf-trees": {
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"plugins": {
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"datasette-cluster-map": {
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"latitude_column": "xlat",
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"longitude_column": "xlng"
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}
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}
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}
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}
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}
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In this case, the above code would return that configuration for ANY table within the ``sf-trees`` database.
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The plugin configuration could also be set at the top level of ``metadata.json``::
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{
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"title": "This is the top-level title in metadata.json",
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"plugins": {
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"datasette-cluster-map": {
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"latitude_column": "xlat",
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"longitude_column": "xlng"
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}
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}
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}
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Now that ``datasette-cluster-map`` plugin configuration will apply to every table in every database.
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Plugin hooks
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------------
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When you implement a plugin hook you can accept any or all of the parameters that are documented as being passed to that hook. For example, you can implement a ``render_cell`` plugin hook like this even though the hook definition defines more parameters than just ``value`` and ``column``:
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.. code-block:: python
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@hookimpl
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def render_cell(value, column):
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if column == "stars":
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return "*" * int(value)
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The full list of available plugin hooks is as follows.
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.. _plugin_hook_prepare_connection:
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prepare_connection(conn)
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~~~~~~~~~~~~~~~~~~~~~~~~
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``conn`` - sqlite3 connection object
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The connection that is being opened
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This hook is called when a new SQLite database connection is created. You can
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use it to `register custom SQL functions <https://docs.python.org/2/library/sqlite3.html#sqlite3.Connection.create_function>`_,
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aggregates and collations. For example:
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.. code-block:: python
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from datasette import hookimpl
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import random
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@hookimpl
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def prepare_connection(conn):
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conn.create_function('random_integer', 2, random.randint)
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This registers a SQL function called ``random_integer`` which takes two
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arguments and can be called like this::
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select random_integer(1, 10);
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.. _plugin_hook_prepare_jinja2_environment:
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prepare_jinja2_environment(env)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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``env`` - jinja2 Environment
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The template environment that is being prepared
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This hook is called with the Jinja2 environment that is used to evaluate
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Datasette HTML templates. You can use it to do things like `register custom
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template filters <http://jinja.pocoo.org/docs/2.10/api/#custom-filters>`_, for
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example:
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.. code-block:: python
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from datasette import hookimpl
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@hookimpl
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def prepare_jinja2_environment(env):
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env.filters['uppercase'] = lambda u: u.upper()
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You can now use this filter in your custom templates like so::
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Table name: {{ table|uppercase }}
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.. _plugin_hook_extra_css_urls:
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extra_css_urls(template, database, table, datasette)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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``template`` - string
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The template that is being rendered, e.g. ``database.html``
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``database`` - string or None
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The name of the database
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``table`` - string or None
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The name of the table
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``datasette`` - Datasette instance
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You can use this to access plugin configuration options via ``datasette.plugin_config(your_plugin_name)``
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Return a list of extra CSS URLs that should be included on the page. These can
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take advantage of the CSS class hooks described in :ref:`customization`.
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This can be a list of URLs:
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.. code-block:: python
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from datasette import hookimpl
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@hookimpl
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def extra_css_urls():
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return [
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'https://stackpath.bootstrapcdn.com/bootstrap/4.1.0/css/bootstrap.min.css'
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]
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Or a list of dictionaries defining both a URL and an
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`SRI hash <https://www.srihash.org/>`_:
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.. code-block:: python
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from datasette import hookimpl
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@hookimpl
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def extra_css_urls():
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return [{
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'url': 'https://stackpath.bootstrapcdn.com/bootstrap/4.1.0/css/bootstrap.min.css',
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'sri': 'sha384-9gVQ4dYFwwWSjIDZnLEWnxCjeSWFphJiwGPXr1jddIhOegiu1FwO5qRGvFXOdJZ4',
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}]
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.. _plugin_hook_extra_js_urls:
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extra_js_urls(template, database, table, datasette)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Same arguments as ``extra_css_urls``.
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This works in the same way as ``extra_css_urls()`` but for JavaScript. You can
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return either a list of URLs or a list of dictionaries:
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.. code-block:: python
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from datasette import hookimpl
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@hookimpl
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def extra_js_urls():
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return [{
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'url': 'https://code.jquery.com/jquery-3.3.1.slim.min.js',
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'sri': 'sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo',
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}]
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You can also return URLs to files from your plugin's ``static/`` directory, if
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you have one:
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.. code-block:: python
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from datasette import hookimpl
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@hookimpl
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def extra_js_urls():
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return [
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'/-/static-plugins/your_plugin/app.js'
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]
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.. _plugin_hook_publish_subcommand:
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publish_subcommand(publish)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~
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``publish`` - Click publish command group
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The Click command group for the ``datasette publish`` subcommand
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This hook allows you to create new providers for the ``datasette publish``
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command. Datasette uses this hook internally to implement the default ``now``
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and ``heroku`` subcommands, so you can read
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`their source <https://github.com/simonw/datasette/tree/master/datasette/publish>`_
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to see examples of this hook in action.
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Let's say you want to build a plugin that adds a ``datasette publish my_hosting_provider --api_key=xxx mydatabase.db`` publish command. Your implementation would start like this:
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.. code-block:: python
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from datasette import hookimpl
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from datasette.common import add_common_publish_arguments_and_options
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import click
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@hookimpl
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def publish_subcommand(publish):
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@publish.command()
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@add_common_publish_arguments_and_options
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@click.option(
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"-k",
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"--api_key",
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help="API key for talking to my hosting provider",
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)
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def my_hosting_provider(
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files,
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metadata,
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extra_options,
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branch,
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template_dir,
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plugins_dir,
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static,
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install,
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version_note,
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title,
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license,
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license_url,
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source,
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source_url,
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api_key,
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):
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# Your implementation goes here
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.. _plugin_hook_render_cell:
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render_cell(value, column, table, database, datasette)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Lets you customize the display of values within table cells in the HTML table view.
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``value`` - string, integer or None
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The value that was loaded from the database
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``column`` - string
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The name of the column being rendered
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``table`` - string or None
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The name of the table - or ``None`` if this is a custom SQL query
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``database`` - string
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The name of the database
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``datasette`` - Datasette instance
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You can use this to access plugin configuration options via ``datasette.plugin_config(your_plugin_name)``
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If your hook returns ``None``, it will be ignored. Use this to indicate that your hook is not able to custom render this particular value.
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If the hook returns a string, that string will be rendered in the table cell.
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If you want to return HTML markup you can do so by returning a ``jinja2.Markup`` object.
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Datasette will loop through all available ``render_cell`` hooks and display the value returned by the first one that does not return ``None``.
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Here is an example of a custom ``render_cell()`` plugin which looks for values that are a JSON string matching the following format::
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{"href": "https://www.example.com/", "label": "Name"}
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If the value matches that pattern, the plugin returns an HTML link element:
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.. code-block:: python
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from datasette import hookimpl
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import jinja2
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import json
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@hookimpl
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def render_cell(value):
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# Render {"href": "...", "label": "..."} as link
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if not isinstance(value, str):
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return None
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stripped = value.strip()
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if not stripped.startswith("{") and stripped.endswith("}"):
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return None
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try:
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data = json.loads(value)
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except ValueError:
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return None
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if not isinstance(data, dict):
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return None
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if set(data.keys()) != {"href", "label"}:
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return None
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href = data["href"]
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if not (
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href.startswith("/") or href.startswith("http://")
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or href.startswith("https://")
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):
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return None
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return jinja2.Markup('<a href="{href}">{label}</a>'.format(
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href=jinja2.escape(data["href"]),
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label=jinja2.escape(data["label"] or "") or " "
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))
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.. _plugin_hook_extra_body_script:
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extra_body_script(template, database, table, datasette)
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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``template`` - string
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The template that is being rendered, e.g. ``database.html``
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``database`` - string or None
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The name of the database, or ``None`` if the page does not correspond to a database (e.g. the root page)
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``table`` - string or None
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The name of the table, or ``None`` if the page does not correct to a table
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``datasette`` - Datasette instance
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You can use this to access plugin configuration options via ``datasette.plugin_config(your_plugin_name)``
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Extra JavaScript to be added to a ``<script>`` block at the end of the ``<body>`` element on the page.
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The ``template``, ``database`` and ``table`` options can be used to return different code depending on which template is being rendered and which database or table are being processed.
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The ``datasette`` instance is provided primarily so that you can consult any plugin configuration options that may have been set, using the ``datasette.plugin_config(plugin_name)`` method documented above.
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The string that you return from this function will be treated as "safe" for inclusion in a ``<script>`` block directly in the page, so it is up to you to apply any necessary escaping.
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