[#9] Make retrieval of Open Forms choices lazy

openformsclient/models.py

@@ -5,7 +5,7 @@
 from django.db.models.fields import BLANK_CHOICE_DASH
 from django.forms.fields import TypedChoiceField
 from django.forms.widgets import Select
-from django.utils.functional import cached_property
+from django.utils.functional import cached_property, lazy
 from django.utils.text import capfirst
 from django.utils.translation import gettext_lazy as _
 
@@ -107,8 +107,7 @@ def formfield(self, **kwargs):
             "widget": Select,
         }
 
-        if self.choices is None:
-            defaults["choices"] = self.get_choices(include_blank=self.blank)
+        defaults["choices"] = self.get_choices(include_blank=self.blank)
         defaults["coerce"] = self.to_python
 
         return TypedChoiceField(**defaults)
@@ -120,25 +119,27 @@ def get_choices(
         limit_choices_to=None,
         ordering=(),
     ):
-        cache_key = f"openformsclient.models.OpenFormsFieldMixin.get_choices__use_uuids_{self.use_uuids}"
-
-        choices = cache.get(cache_key)
-        if choices is None:
-            try:
-                choices = get_form_choices(use_uuids=self.use_uuids)
-            except Exception as e:
-                logger.exception(e)
-                choices = []
-            else:
-                cache.set(cache_key, choices, timeout=60)
-
-        if choices:
-            if include_blank:
-                blank_defined = any(choice in ("", None) for choice, _ in choices)
-                if not blank_defined:
-                    choices = blank_choice + choices
-
-        return choices
+        def _fetch():
+            cache_key = f"openformsclient.models.OpenFormsBaseField.get_choices__use_uuids_{self.use_uuids}"
+
+            choices = cache.get(cache_key)
+            if choices is None:
+                try:
+                    choices = get_form_choices(use_uuids=self.use_uuids)
+                except Exception as exc:
+                    logger.exception(exc)
+                    choices = []
+                else:
+                    cache.set(cache_key, choices, timeout=60)
+
+            if choices:
+                if include_blank:
+                    blank_defined = any(choice in ("", None) for choice, _ in choices)
+                    if not blank_defined:
+                        choices = blank_choice + choices
+            return choices
+
+        return lazy(_fetch, list)
 
 
 class OpenFormsUUIDField(OpenFormsBaseField, models.UUIDField):

setup.cfg

@@ -41,6 +41,7 @@ tests_require =
     isort
     black
     flake8
+    time-machine
 
 [options.packages.find]
 include =
@@ -56,6 +57,7 @@ tests =
     isort
     black
     flake8
+    time-machine
 pep8 = flake8
 coverage = pytest-cov
 docs =

tests/test_integration.py

@@ -1,9 +1,11 @@
+import datetime
 from uuid import UUID
 
 from django.forms import modelform_factory
 from django.test import TestCase
 
 import requests_mock
+import time_machine
 
 from openformsclient.models import Configuration
 from testapp.models import Page
@@ -41,7 +43,7 @@ def test_values_in_slug_form_field(self, m):
         page_form = PageForm()
 
         self.assertListEqual(
-            page_form.fields["form_slug"].choices,
+            list(page_form.fields["form_slug"].choices),
             [
                 ("", "---------"),
                 ("test-1", "Test 1"),
@@ -56,7 +58,7 @@ def test_values_in_uuid_form_field(self, m):
         page_form = PageForm()
 
         self.assertListEqual(
-            page_form.fields["form_uuid"].choices,
+            list(page_form.fields["form_uuid"].choices),
             [
                 ("", "---------"),
                 ("f4423c99-6341-442e-aedc-b47779579f4d", "Test 1"),
@@ -129,3 +131,21 @@ def test_slug_form_field_blank(self, m):
 
         self.assertEqual(Page.objects.count(), 1)
         self.assertEqual(Page.objects.get().form_slug, "")
+
+    def test_form_retrieval_cache(self, m):
+        self._prepare_mock(m)
+
+        PageForm = modelform_factory(Page, fields=["form_slug"])
+        page_form = PageForm()
+
+        with time_machine.travel(0) as traveller:
+            list(page_form.fields["form_slug"].choices)
+            list(page_form.fields["form_slug"].choices)
+
+            self.assertEqual(m.call_count, 1)
+
+            traveller.shift(datetime.timedelta(seconds=60))
+
+            list(page_form.fields["form_slug"].choices)
+
+            self.assertEqual(m.call_count, 2)