Fixed #10941 -- Added {% query_string %} template tag.

1 files changed, 41 insertions, 0 deletions

diff --git a/django/template/defaulttags.py b/django/template/defaulttags.py
index 79c10232bb..188bdf8c05 100644
--- a/django/template/defaulttags.py
+++ b/django/template/defaulttags.py
@@ -10,6 +10,7 @@ from itertools import groupby
 from django.conf import settings
 from django.utils import timezone
 from django.utils.html import conditional_escape, escape, format_html
+from django.utils.itercompat import is_iterable
 from django.utils.lorem_ipsum import paragraphs, words
 from django.utils.safestring import mark_safe
 
@@ -1167,6 +1168,46 @@ def now(parser, token):
     return NowNode(format_string, asvar)
 
 
+@register.simple_tag(takes_context=True)
+def query_string(context, query_dict=None, **kwargs):
+    """
+    Add, remove, and change parameters of a ``QueryDict`` and return the result
+    as a query string. If the ``query_dict`` argument is not provided, default
+    to ``request.GET``.
+
+    For example::
+
+        {% query_string foo=3 %}
+
+    To remove a key::
+
+        {% query_string foo=None %}
+
+    To use with pagination::
+
+        {% query_string page=page_obj.next_page_number %}
+
+    A custom ``QueryDict`` can also be used::
+
+        {% query_string my_query_dict foo=3 %}
+    """
+    if query_dict is None:
+        query_dict = context.request.GET
+    query_dict = query_dict.copy()
+    for key, value in kwargs.items():
+        if value is None:
+            if key in query_dict:
+                del query_dict[key]
+        elif is_iterable(value) and not isinstance(value, str):
+            query_dict.setlist(key, value)
+        else:
+            query_dict[key] = value
+    if not query_dict:
+        return ""
+    query_string = query_dict.urlencode()
+    return f"?{query_string}"
+
+
 @register.tag
 def regroup(parser, token):
     """