renderers: add debug content to templates when DEBUG is True (fixes #5092)

The debug content for the data_source renderer is (using pseudo-template
code):

<!-- DEBUG:
config: {{ blurp.config|pprint }}
{% for each source %}
slug {{ source.slug }}: {% source.content|pprint %}
{% endfor %}
-->

The debug content is extracted from a template context variable named
'blurp_debug__' that any blurp renderer can set when DEBUG is True.

src/cmsplugin_blurp/renderers/data_source.py

@@ -3,6 +3,7 @@ import hashlib
 from xml.etree import ElementTree as ET
 import time
 import threading
+import pprint
 
 import feedparser
 import requests
@@ -81,11 +82,28 @@ class Renderer(template.TemplateRenderer):
             slug = '{0}.{1}'.format(self.slug, source['slug'])
             data = Data(slug, self.config, source, context)
             yield source['slug'], data
+        if settings.TEMPLATE_DEBUG:
+            yield 'blurp_debug__', '\n'.join(self.debug_content(context))
+
+    def debug_content(self, context):
+        try:
+            yield u'config: {0}'.format(pprint.pformat(self.config))
+        except Exception, e:
+            yield u'config: pformat failed {0!r}'.format(e)
+        for source in self.config.get('sources', []):
+            slug = source.get('slug')
+            if not slug:
+                continue
+            try:
+                yield u'slug {0!r}: {1}'.format(slug,
+                        pprint.pformat(context.get(slug)))
+            except Exception, e:
+                yield u'slug {0!r}: pformat failed {1!r}'.format(slug, e)
 
     def render(self, context):
         for slug, source in self.get_sources(context):
             context[slug] = source
-        return context
+        return super(Renderer, self).render(context)
 
 class Data(object):
     '''Encapsulate data from a source'''
@@ -317,3 +335,4 @@ class Data(object):
 
     def __call__(self):
         return self.get_content()
+

src/cmsplugin_blurp/renderers/template.py

@@ -2,7 +2,8 @@ import logging
 
 from django.core.exceptions import ImproperlyConfigured
 from django.template.loader import get_template
-from django.template import TemplateDoesNotExist, Template
+from django.template import Template
+from django.conf import settings
 
 from .base import BaseRenderer
 
@@ -20,16 +21,28 @@ class TemplateRenderer(BaseRenderer):
             raise ImproperlyConfigured('{0} configuration is missing a template key: {1!r}'.format(
                     cls.__name__, config))
 
+    def render(self, context):
+        if settings.TEMPLATE_DEBUG:
+            context['__blurb'] = self
+        return context
+
     def render_template(self):
         '''First try to get a template by path, then compile the inline
            template, and if none of that works show an error message.'''
 
         if 'template_name' in self.config:
             try:
-                return get_template(self.config['template_name'])
+                template = get_template(self.config['template_name'])
             except TemplateDoesNotExist:
                 pass
-        if 'template' in self.config:
-            return Template(self.config['template'])
-        log.error('template not found: %r', self.config)
-        return 'cmsplugin_blurp/template_not_found.html'
+        elif 'template' in self.config:
+            template = Template(self.config['template'])
+        else:
+            log.error('template not found: %r', self.config)
+            template = 'cmsplugin_blurp/template_not_found.html'
+        if settings.TEMPLATE_DEBUG:
+            if not hasattr(template, 'render'):
+                template = get_template(template)
+            debug_template = Template('<!-- DEBUG:\n{{ blurp_debug__ }}\n-->')
+            template.nodelist.extend(debug_template.nodelist)
+        return template