add json_script template tag (from django 2.1)

combo_plugin_gnm/templatetags/gnm.py

@@ -17,6 +17,7 @@
 
 from collections import OrderedDict
 import datetime
+import json
 import math
 import operator
 import random
@@ -27,8 +28,10 @@ from requests import RequestException
 
 from django import template
 from django.conf import settings
+from django.core.serializers.json import DjangoJSONEncoder
 from django.utils.dateparse import parse_datetime
 from django.utils.http import quote
+from django.utils.html import format_html
 from django.utils.text import slugify
 from django.utils.timezone import is_naive, make_aware
 from django.utils.safestring import mark_safe
@@ -674,3 +677,18 @@ def gnm_airquality_map(context):
     map_cell.max_zoom = '19'
     context.push(map_cell.get_cell_extra_context({}))
     return context
+
+_json_script_escapes = {
+    ord('>'): '\\u003E',
+    ord('<'): '\\u003C',
+    ord('&'): '\\u0026',
+}
+
+@register.filter(is_safe=True)
+def json_script(value, element_id):
+    json_str = json.dumps(value, cls=DjangoJSONEncoder)
+    json_str = json_str.replace('>', '\\u003E').replace('<', '\\u003C').replace('&', '\\u0026')
+    return format_html(
+        '<script id="{}" type="application/json">{}</script>',
+        element_id, mark_safe(json_str)
+    )