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can_render mechanism for register_output_renderer, closes #770

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Simon Willison 2020-05-27 22:57:05 -07:00
commit 5ab411c733
6 changed files with 108 additions and 18 deletions
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docs/plugins.rst
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@ -744,14 +744,17 @@ Registers a new output renderer, to output data in a custom format. The hook fun
def register_output_renderer(datasette):
return {
"extension": "test",
"render": render_test
"render": render_demo,
"can_render": can_render_demo, # Optional
}
This will register ``render_test`` to be called when paths with the extension ``.test`` (for example ``/database.test``, ``/database/table.test``, or ``/database/table/row.test``) are requested.
This will register ``render_demo`` to be called when paths with the extension ``.test`` (for example ``/database.test``, ``/database/table.test``, or ``/database/table/row.test``) are requested.
``render_test`` is a Python function. It can be a regular function or an ``async def render_test()`` awaitable function, depending on if it needs to make any asynchronous calls.
``render_demo`` is a Python function. It can be a regular function or an ``async def render_demo()`` awaitable function, depending on if it needs to make any asynchronous calls.
When a request is received, the callback function is called with zero or more of the following arguments. Datasette will inspect your callback function and pass arguments that match its function signature.
``can_render_demo`` is a Python function (or ``async def`` function) which acepts the same arguments as ``render_demo`` but just returns ``True`` or ``False``. It lets Datasette know if the current SQL query can be represented by the plugin - and hence influnce if a link to this output format is displayed in the user interface. If you omit the ``"can_render"`` key from the dictionary every query will be treated as being supported by the plugin.
When a request is received, the ``"render"`` callback function is called with zero or more of the following arguments. Datasette will inspect your callback function and pass arguments that match its function signature.
``datasette`` - :ref:`internals_datasette`
For accessing plugin configuration and executing queries.
@ -798,7 +801,7 @@ A simple example of an output renderer callback function:
.. code-block:: python
def render_test():
def render_demo():
return {
"body": "Hello World"
}
@ -807,7 +810,7 @@ Here is a more complex example:
.. code-block:: python
async def render_test(datasette, columns, rows):
async def render_demo(datasette, columns, rows):
db = next(iter(datasette.databases.values()))
result = await db.execute("select sqlite_version()")
first_row = " | ".join(columns)
@ -821,6 +824,13 @@ Here is a more complex example:
"headers": {"x-sqlite-version": result.first()[0]},
}
And here is an example ``can_render`` function which returns ``True`` only if the query results contain the columns ``atom_id``, ``atom_title`` and ``atom_updated``:
.. code-block:: python
def can_render_demo(columns):
return {"atom_id", "atom_title", "atom_updated"}.issubset(columns)
Examples: `datasette-atom <https://github.com/simonw/datasette-atom>`_, `datasette-ics <https://github.com/simonw/datasette-ics>`_
.. _plugin_register_facet_classes: