Backport/2.6/docs default lists (#56666)

* 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

@@ -24,6 +24,7 @@ __metaclass__ = type
 
 import datetime
 import glob
+import json
 import optparse
 import os
 import re
@@ -334,6 +335,10 @@ 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['convert_symbols_to_format'] = rst_ify

docs/templates/plugin.rst.j2

@@ -153,7 +153,7 @@ 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 #}