Variables from extra_template_vars() not exposed in _context=1

[simonw]

The _context=1 debugging mode does not show variables that should have been added to the context by the extra_template_vars() plugin hook.

[simonw]

Here's why:

datasette/datasette/views/base.py

Lines 84 to 96 in 613f6fa

	if (
	request
	and request.args.get("_context")
	and self.ds.config("template_debug")
	):
	return Response.html(
	"<pre>{}</pre>".format(
	jinja2.escape(json.dumps(template_context, default=repr, indent=4))
	)
	)
	return Response.html(
	await self.ds.render_template(template, template_context, request=request)
	)

It's bypassing the .ds.render_template() call - and that's where the plugin hook is executed:

datasette/datasette/app.py

Lines 520 to 564 in 613f6fa

	async def render_template(
	self, templates, context=None, request=None, view_name=None
	):
	context = context or {}
	if isinstance(templates, Template):
	template = templates
	select_templates = []
	else:
	if isinstance(templates, str):
	templates = [templates]
	template = self.jinja_env.select_template(templates)
	select_templates = [
	"{}{}".format(
	"*" if template_name == template.name else "", template_name
	)
	for template_name in templates
	]
	body_scripts = []
	# pylint: disable=no-member
	for script in pm.hook.extra_body_script(
	template=template.name,
	database=context.get("database"),
	table=context.get("table"),
	view_name=view_name,
	datasette=self,
	):
	body_scripts.append(Markup(script))
	extra_template_vars = {}
	# pylint: disable=no-member
	for extra_vars in pm.hook.extra_template_vars(
	template=template.name,
	database=context.get("database"),
	table=context.get("table"),
	view_name=view_name,
	request=request,
	datasette=self,
	):
	if callable(extra_vars):
	extra_vars = extra_vars()
	if asyncio.iscoroutine(extra_vars):
	extra_vars = await extra_vars
	assert isinstance(extra_vars, dict), "extra_vars is of type {}".format(
	type(extra_vars)
	)

[simonw]

So I should move the template_debug and _context logic into the render_template() method.

[simonw]

Fixed.