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Fix/missing context vars #453

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Fix/missing context vars #453

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f8e451a
Add resolve_variable simple_tag for missing template vars
hazra1991 Sep 4, 2025
d5901ea
Add test for resolve_variable
hazra1991 Sep 4, 2025
bd9167d
refactor: rename resolve_variable and improve resolution logic
hazra1991 Sep 5, 2025
9c1cd7b
refactor: variable name
hazra1991 Sep 7, 2025
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3 changes: 3 additions & 0 deletions admin_interface/templates/admin/base_site.html
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Original file line number Diff line number Diff line change
Expand Up @@ -146,6 +146,9 @@
{% if theme.list_filter_highlight %} list-filter-highlight {% endif %}
{% if theme.list_filter_sticky %} list-filter-sticky {% endif %}

{% resolve_variable "adminform" as adminform %}
{% resolve_variable "inline_admin_formsets" as inline_admin_formsets %}

{% if adminform and inline_admin_formsets %}
{% admin_interface_use_changeform_tabs adminform inline_admin_formsets as admin_interface_use_changeform_tabs %}
{% if admin_interface_use_changeform_tabs %}
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5 changes: 5 additions & 0 deletions admin_interface/templatetags/admin_interface_tags.py
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Original file line number Diff line number Diff line change
Expand Up @@ -188,6 +188,11 @@ def admin_interface_use_changeform_tabs(adminform, inline_forms):
return has_tabs


@register.simple_tag(takes_context=True)
def resolve_variable(context, var_name, default=""):
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@fabiocaccamo fabiocaccamo Sep 4, 2025

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Could you please rename the template tag to admin_interface_resolve_variable?

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@hazra1991 hazra1991 Sep 5, 2025

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Done
renamed the template tag to admin_interface_resolve_variable as suggested.

return context.get(var_name, default)
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@fabiocaccamo fabiocaccamo Sep 4, 2025

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This works only for top-level context keys. It doesn't resolve dotted variables like user.username, the correct approach is:

try:
    return template.Variable(var_name).resolve(context)
except VariableDoesNotExist:
    return default

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@hazra1991 hazra1991 Sep 5, 2025

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Thanks for the suggestion!

I initially considered using template.Variable(var_name).resolve(context) directly, but the issue is that when a variable (or part of a dotted lookup like var.dottedvar) is missing, Variable.resolve() raises VariableDoesNotExist, which gets logged by Django and pollutes the logs. which brings us to the same issue that we are trying to prevent .

To avoid this, I’ve added a lightweight pre-check that verifies variable (normal and dotted) exists in the context.

If it does, I then delegate to Variable.resolve() so Django still handles callables, translations, etc. If not, I return the default immediately.



@register.filter
def admin_interface_slugify(name):
return slugify(str(name or ""))
31 changes: 31 additions & 0 deletions tests/test_resolve_variable.py
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@fabiocaccamo fabiocaccamo Sep 6, 2025

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Just a small thing: please use always the same variable name for coherence. I see sometimes you use res, sometimes result. Better to choose one (result) and use it everywhere to keep the code more clear.

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@hazra1991 hazra1991 Sep 7, 2025

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Acknowledged, and thank you for pointing that out !

Original file line number Diff line number Diff line change
@@ -0,0 +1,31 @@
from django.template import Context, Template
from django.test import SimpleTestCase


class ResolveVariableTagTests(SimpleTestCase):
def render_template(self, tpl, context=None):
if context is None:
context = {}
return (
Template("{% load admin_interface_tags %}" + tpl)
.render(Context(context))
.strip()
)

def test_returns_existing_variable(self):
out = self.render_template(
'{% resolve_variable "myvar" as result %}{{ result }}', {"myvar": "hello"}
)
self.assertEqual(out, "hello")

def test_returns_default_when_missing(self):
out = self.render_template(
'{% resolve_variable "missingvar" as result %}{{ result }}'
)
self.assertEqual(out, "")

def test_returns_custom_default(self):
out = self.render_template(
'{% resolve_variable "missingvar" "fallback" as result %}{{ result }}'
)
self.assertEqual(out, "fallback")