feat: Handle Undefined/None in make_href filter

capella_model_explorer/backend/explorer.py

@@ -18,7 +18,12 @@
 from fastapi.responses import HTMLResponse
 from fastapi.staticfiles import StaticFiles
 from fastapi.templating import Jinja2Templates
-from jinja2 import Environment, TemplateSyntaxError, FileSystemLoader
+from jinja2 import (
+    Environment,
+    FileSystemLoader,
+    TemplateSyntaxError,
+    is_undefined,
+)
 
 esc = markupsafe.escape
 
@@ -65,6 +70,9 @@ def __finalize(self, markup: t.Any) -> object:
         )
 
     def __make_href_filter(self, obj: object) -> str | None:
+        if is_undefined(obj) or obj is None:
+            return "#"
+
         if isinstance(obj, capellambse.model.ElementList):
             raise TypeError("Cannot make an href to a list of elements")
         if not isinstance(

templates/common_macros.html.j2

@@ -33,9 +33,9 @@
 <ul>
 {% for rel in rels %}
     <li>
-        <a href="{{ rel.type | make_href if rel.type else '#' }}">{{rel.type.long_name }}</a> 
-        {{ rel.target.__class__.__name__ }} 
-        <a href="{{ rel.target | make_href  if rel.target else '#' }}">{{ rel.target.name }}</a>
+        <a href="{{ rel.type | make_href }}">{{rel.type.long_name }}</a>
+        {{ rel.target.__class__.__name__ }}
+        <a href="{{ rel.target | make_href }}">{{ rel.target.name }}</a>
     </li>
 {% endfor %}
 </ul>