WIP: instrument the jinja render function (more)

It instruments the single template render, but not the inherited
templates and I'm guessing not the included templates either.
I suspect we're going to have to patch jinja templates more robustly
than relying on the django jinja backend template class.

debug_toolbar/panels/templates/jinja2.py

@@ -0,0 +1,22 @@
+import functools
+
+from django.template.backends.jinja2 import Template as JinjaTemplate
+from django.template.context import make_context
+from django.test.signals import template_rendered
+
+
+def patch_jinja_render():
+    orig_render = JinjaTemplate.render
+
+    @functools.wraps(orig_render)
+    def wrapped_render(self, context=None, request=None):
+        print(self.template.name)
+        self.name = self.template.name
+        template_rendered.send(
+            sender=self, template=self, context=make_context(context, request)
+        )
+        return orig_render(self, context, request)
+
+    if JinjaTemplate.render != wrapped_render:
+        JinjaTemplate.original_render = JinjaTemplate.render
+        JinjaTemplate.render = wrapped_render

debug_toolbar/panels/templates/panel.py

@@ -14,6 +14,7 @@
 from debug_toolbar.panels import Panel
 from debug_toolbar.panels.sql.tracking import SQLQueryTriggered, allow_sql
 from debug_toolbar.panels.templates import views
+from debug_toolbar.panels.templates.jinja2 import patch_jinja_render
 
 # Monkey-patch to enable the template_rendered signal. The receiver returns
 # immediately when the panel is disabled to keep the overhead small.
@@ -25,6 +26,7 @@
     Template.original_render = Template._render
     Template._render = instrumented_test_render
 
+patch_jinja_render()
 
 # Monkey-patch to store items added by template context processors. The
 # overhead is sufficiently small to justify enabling it unconditionally.