Added safe_var function

filter_plugins/safe_var.py

@@ -0,0 +1,27 @@
+# file: filter_plugins/safe_var.py
+
+from jinja2 import Undefined
+
+def safe_var(value):
+    """
+    Returns the original value unless it is None or Jinja2‐Undefined.
+    Catches all exceptions and returns an empty string on error.
+    """
+    try:
+        # If the value is an Undefined from Jinja2, treat it as missing
+        if isinstance(value, Undefined):
+            return ''
+        # Treat None as missing as well
+        if value is None:
+            return ''
+        # Otherwise return the actual value
+        return value
+    except Exception:
+        # Catch any other errors and return empty string
+        return ''
+
+class FilterModule(object):
+    def filters(self):
+        return {
+            'safe_var': safe_var
+        }

group_vars/all/15_about.yml

@@ -9,12 +9,18 @@ defaults_service_provider:
       city:         "Cybertown"
       postal_code:  "00001"
       country:      "Nexusland"
-    logo:           "{{applications.assets_server.url}}/logo.png"
+    logo: >-
+      {{ (applications.assets_server.url  | safe_var ~ '/logo.png')
+        if applications.assets_server.url  | safe_var else '' }}
   platform:    
     titel:          "CyMaIS Demo"
     subtitel:       "The Future of Self-Hosted Infrastructure. Secure. Automated. Sovereign."
-    logo:           "{{applications.assets_server.url}}/img/logo.png"
-    favicon:        "{{applications.assets_server.url}}/img/favicon.ico"
+    logo: >-
+      {{ (applications.assets_server.url  | safe_var ~ '/logo.png')
+        if applications.assets_server.url  | safe_var else '' }}
+    favicon: >-
+      {{ (applications.assets_server.url  | safe_var ~ '/favicon.ico')
+        if applications.assets_server.url  | safe_var else '' }}
   contact:
     bluesky: >-
       {{ ('@' ~ users.administrator.username ~ '.' ~ domains[application_id]['api'])

roles/nginx-serve-assets/vars/configuration.yml

@@ -1,2 +1,4 @@
-source_directory: "{{ playbook_dir }}/assets"                           # Directory from which the assets will be copied
-url:              "{{ web_protocol }}://{{domains.file_server}}/assets" # Public address of the assets directory
+source_directory: "{{ playbook_dir }}/assets"                             # Directory from which the assets will be copied
+url: >-
+  {{ (web_protocol ~ '://' ~ domains.file_server | safe_var ~ '/assets')
+     if applications.assets_server.url | safe_var else '' }}

tests/unit/test_safe_var.py

@@ -0,0 +1,44 @@
+import unittest
+import sys
+import os
+from jinja2 import Undefined
+
+# Ensure filter_plugins directory is on the path
+sys.path.insert(
+    0,
+    os.path.abspath(os.path.join(os.path.dirname(__file__), '../../filter_plugins'))
+)
+
+from safe_var import FilterModule
+
+class TestSafeVarFilter(unittest.TestCase):
+    def setUp(self):
+        # Retrieve the safe_var filter function
+        self.filter = FilterModule().filters()['safe_var']
+
+    def test_returns_non_empty_string(self):
+        self.assertEqual(self.filter('hello'), 'hello')
+
+    def test_returns_empty_string(self):
+        self.assertEqual(self.filter(''), '')
+
+    def test_returns_empty_for_none(self):
+        self.assertEqual(self.filter(None), '')
+
+    def test_returns_empty_for_jinja_undefined(self):
+        # Instantiate an Undefined without arguments
+        undef = Undefined()
+        self.assertEqual(self.filter(undef), '')
+
+    def test_returns_zero_for_zero(self):
+        # 0 is falsey but not None or Undefined, so safe_var returns it
+        self.assertEqual(self.filter(0), 0)
+
+    def test_returns_list_and_dict_unchanged(self):
+        data = {'key': 'value'}
+        self.assertEqual(self.filter(data), data)
+        lst = [1, 2, 3]
+        self.assertEqual(self.filter(lst), lst)
+
+if __name__ == '__main__':
+    unittest.main()