From 7946a926b4ce311ce217667d6ca32a1ad61e1e62 Mon Sep 17 00:00:00 2001
From: Étienne Loks <etienne.loks@iggdrasil.net>
Date: Tue, 17 Feb 2026 15:57:37 +0100
Subject: ⚡ templates: `list_filter` custom tag - improve performance for
 json_sections
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---
 ishtar_common/models_common.py               |  8 ++++++++
 ishtar_common/templatetags/ishtar_helpers.py | 25 +++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/ishtar_common/models_common.py b/ishtar_common/models_common.py
index a94eadb80..10c564024 100644
--- a/ishtar_common/models_common.py
+++ b/ishtar_common/models_common.py
@@ -1339,6 +1339,8 @@ class JsonData(models.Model, CachedGen):
 
     @property
     def json_sections(self):
+        if getattr(self, "__json_sections", None):
+            return self.__json_sections
         sections = []
         try:
             content_type = ContentType.objects.get_for_model(self)
@@ -1382,6 +1384,12 @@ class JsonData(models.Model, CachedGen):
                 # if section name is identical it is the same
                 sections.append((section_name, []))
             sections[-1][1].append((field.name, value))
+        # clean
+        sections = [
+            (label or "", section) for label, section in sections
+            if any(1 for __, value in section if value)
+        ]
+        self.__json_sections = sections
         return sections
 
     @classmethod
diff --git a/ishtar_common/templatetags/ishtar_helpers.py b/ishtar_common/templatetags/ishtar_helpers.py
index 8c0c30761..de1d55d2e 100644
--- a/ishtar_common/templatetags/ishtar_helpers.py
+++ b/ishtar_common/templatetags/ishtar_helpers.py
@@ -142,3 +142,28 @@ def limit_label(value, limit=120):
     return mark_safe(
         f'<span title="{value}">{value[:(limit - 4)]} (...)</span>'
     )
+
+
+@register.simple_tag
+def list_filter(lst, filter_value, item_number=None):
+    """
+    Filter a list (`lst`) by item containing `filter_value`.
+    If `filter_value` begin with "-:" filter by item NOT containing `filter_value`.
+    If `item_number` (int) is provided, the list contains a list and filter is made on the
+    `item_number` value of this list
+    """
+    reverse = False
+    if filter_value.startswith("-:"):
+        filter_value = filter_value[2:]
+        reverse = True
+    if not reverse:
+        if item_number is not None:
+            cmp = lambda x: x and x[item_number] and filter_value in x[item_number]
+        else:
+            cmp = lambda x: x and filter_value in x
+    else:
+        if item_number is not None:
+            cmp = lambda x: not x or not x[item_number] or filter_value not in x[item_number]
+        else:
+            cmp = lambda x: not x or filter_value not in x
+    return [item for item in lst if cmp(item)]
-- 
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