[TMP] Add a not that elegant way to show even better diffs for custom fields

This works by manually messing around with the JSON and reindenting a bit.
Please note that this is the best I could come up with.

We create a new list with tuples of (cf_name, cf_value, modified: bool).
If the modified bool is true, then color it correctly (Red/green)

The new templatetag fixindent modifies multi-line custom fields (E.g. selections),
so that the indentation of the object is ok again.

netbox/extras/views.py

@@ -722,17 +722,25 @@ class ObjectChangeView(generic.ObjectView):
             diff_added, diff_removed = deep_compare_dict(prechange_data, instance.postchange_data, exclude=('last_updated'))
             custom_fields_added = diff_added['custom_fields'] if 'custom_fields' in diff_added else None
             custom_fields_removed = diff_removed['custom_fields'] if 'custom_fields' in diff_removed else None
+            cfr_list = []
+            if custom_fields_added:
+                for cf, cf_value in prechange_data['custom_fields'].items():
+                    cfr_list.append((cf, cf_value, cf in custom_fields_added))
+            cfa_list = []
+            if custom_fields_removed:
+                for cf, cf_value in instance.postchange_data['custom_fields'].items():
+                    cfa_list.append((cf, cf_value, cf in custom_fields_removed))
         else:
             diff_added = None
             diff_removed = None
-            custom_fields_added = None
-            custom_fields_removed = None
+            cfa_list = None
+            cfr_list = None
 
         return {
             'diff_added': diff_added,
             'diff_removed': diff_removed,
-            'custom_fields_added': custom_fields_added,
-            'custom_fields_removed': custom_fields_removed,
+            "cfa_list": cfa_list,
+            "cfr_list": cfr_list,
             'next_change': next_change,
             'prev_change': prev_change,
             'related_changes_table': related_changes_table,

netbox/templates/extras/objectchange.html

@@ -119,10 +119,11 @@
             <div class="card-body">
             {% if object.prechange_data %}
                 <pre class="change-data">{% for k, v in object.prechange_data.items %}{% spaceless %}
-                    {% if k != 'custom_fields' or not custom_fields_removed %}
+                    {% if k != 'custom_fields' or not cfr_list %}
                         <span{% if k in diff_removed %} class="removed"{% endif %}>{{ k }}: {{ v|json }}</span>
                     {% else %}
-                        <span class="removed">{{ k }}: {{ custom_fields_removed|json }}</span>
+                    <span>{{ k }}: {</span>{% for cfr_data in cfr_list %}<span{% if cfr_data.2 %} class="removed"{% endif %}>    {{ cfr_data.0|json }}: {{ cfr_data.1|json|fixindent }}</span>
+                    {% endfor %}<span>}</span>
                     {% endif %}
                 {% endspaceless %}{% endfor %}
                 </pre>
@@ -142,10 +143,11 @@
             <div class="card-body">
                 {% if object.postchange_data %}
                     <pre class="change-data">{% for k, v in object.postchange_data.items %}{% spaceless %}
-                        {% if k != 'custom_fields' or not custom_fields_added %}
+                        {% if k != 'custom_fields' or not cfa_list %}
                             <span{% if k in diff_added %} class="added"{% endif %}>{{ k }}: {{ v|json }}</span>
                         {% else %}
-                            <span class="added">{{ k }}: {{ custom_fields_added|json }}</span>
+                            <span>{{ k }}: {</span>{% for cfa_data in cfa_list %}<span{% if cfa_data.2 %} class="added"{% endif %}>    {{ cfa_data.0|json }}: {{ cfa_data.1|json|fixindent }}</span>
+{% endfor %}<span>}</span>
                         {% endif %}
                         {% endspaceless %}{% endfor %}
                     </pre>

netbox/utilities/templatetags/helpers.py

@@ -20,6 +20,7 @@ __all__ = (
     'applied_filters',
     'as_range',
     'divide',
+    'fixindent',
     'get_item',
     'get_key',
     'humanize_megabytes',
@@ -331,3 +332,19 @@ def applied_filters(context, model, form, query_params):
         'applied_filters': applied_filters,
         'save_link': save_link,
     }
+
+
+@register.filter
+def fixindent(value: str) -> str:
+    """
+    Fixes the indentation of multiline strings so they align well
+    within the changelog view.
+    """
+    lines = value.splitlines(keepends=True)
+    # For 1 line, the indentation doesn't need to be fixed
+    if len(lines) == 1:
+        return value
+    ret = lines[0]
+    for line in lines[1:]:
+        ret += f'    {line}'
+    return ret