Render plugin mechanism needs error and truncated fields

[simonw]

While working on:

• New JSON design for query views #2118

It became clear that the render callback function documented here: https://docs.datasette.io/en/0.64.3/plugin_hooks.html#register-output-renderer-datasette

Needs to grow the ability to be told if an error occurred (an error string) and if the results were truncated (a truncated boolean).

[simonw]

Main place the code needs updating is here:

datasette/datasette/views/base.py

Lines 301 to 310 in 5139c08

	result = call_with_supported_arguments(
	self.ds.renderers[_format][0],
	datasette=self.ds,
	columns=data.get("columns") or [],
	rows=data.get("rows") or [],
	sql=data.get("query", {}).get("sql", None),
	query_name=data.get("query_name"),
	database=database,
	table=data.get("table"),
	request=request,

Plus the documentation.

[simonw]

Updated documentation is here: https://docs.datasette.io/en/latest/plugin_hooks.html#register-output-renderer-datasette