Backport/2.7/docs default lists (#56667)

* Improve rendering of default lists (#56041)

(cherry picked from commit 53ed1bfc49)

* Add compat tojson filter for jinja2 versions missing it (#56596)

(cherry picked from commit 3f4a22d8ef)

docs/bin/plugin_formatter.py

@@ -11,6 +11,7 @@ __metaclass__ = type
 
 import datetime
 import glob
+import json
 import optparse
 import os
 import re
@@ -365,6 +366,10 @@ def jinja2_environment(template_dir, typ, plugin_type):
         # Jinja < 2.10
         env.filters['max'] = do_max
 
+    if 'tojson' not in env.filters:
+        # Jinja < 2.9
+        env.filters['tojson'] = json.dumps
+
     templates = {}
     if typ == 'rst':
         env.filters['rst_ify'] = rst_ify

docs/templates/plugin.rst.j2

@@ -155,7 +155,7 @@ Parameters
                     {% endif %}
                     {# Show default value, when multiple choice or no choices #}
                     {% if value.default is defined and value.default not in value.choices %}
-                        <b>Default:</b><br/><div style="color: blue">@{ value.default | escape }@</div>
+                        <b>Default:</b><br/><div style="color: blue">@{ value.default | tojson | escape }@</div>
                     {% endif %}
                 </td>
                 {# configuration #}