FIXED #5899 -- Allowed having the collapsible fieldset and inlines expended on page load.

AUTHORS

@@ -1002,6 +1002,7 @@ answer newbie questions, and generally made Django that much better:
     Terry Huang <terryh.tp@gmail.com>
     thebjorn <bp@datakortet.no>
     Thejaswi Puthraya <thejaswi.puthraya@gmail.com>
+    Theo Poncelet <theo.poncelet99@gmail.com>
     Thijs van Dien <thijs@vandien.net>
     Thom Wiggers
     Thomas Chaumeny <t.chaumeny@gmail.com>

django/contrib/admin/templates/admin/edit_inline/stacked.html

@@ -4,7 +4,7 @@
      data-inline-type="stacked"
      data-inline-formset="{{ inline_admin_formset.inline_formset_data }}">
 <fieldset class="module {{ inline_admin_formset.classes }}" aria-labelledby="{{ inline_admin_formset.formset.prefix }}-heading">
-  {% if inline_admin_formset.is_collapsible %}<details><summary>{% endif %}
+  {% if inline_admin_formset.is_collapsible %}<details {% if 'collapse-open' in inline_admin_formset.classes %}open{% endif %}><summary>{% endif %}
   <h2 id="{{ inline_admin_formset.formset.prefix }}-heading" class="inline-heading">
   {% if inline_admin_formset.formset.max_num == 1 %}
     {{ inline_admin_formset.opts.verbose_name|capfirst }}

django/contrib/admin/templates/admin/edit_inline/tabular.html

@@ -5,7 +5,7 @@
   <div class="tabular inline-related {% if forloop.last %}last-related{% endif %}">
 {{ inline_admin_formset.formset.management_form }}
 <fieldset class="module {{ inline_admin_formset.classes }}" aria-labelledby="{{ inline_admin_formset.formset.prefix }}-heading">
-  {% if inline_admin_formset.is_collapsible %}<details><summary>{% endif %}
+  {% if inline_admin_formset.is_collapsible %}<details {% if 'collapse-open' in inline_admin_formset.classes %}open{% endif %}><summary>{% endif %}
   <h2 id="{{ inline_admin_formset.formset.prefix }}-heading" class="inline-heading">
   {% if inline_admin_formset.formset.max_num == 1 %}
     {{ inline_admin_formset.opts.verbose_name|capfirst }}

django/contrib/admin/templates/admin/includes/fieldset.html

@@ -1,6 +1,6 @@
 <fieldset class="module aligned {{ fieldset.classes }}"{% if fieldset.name %} aria-labelledby="{{ prefix }}-{{ id_prefix}}-{{ id_suffix }}-heading"{% endif %}>
     {% if fieldset.name %}
-        {% if fieldset.is_collapsible %}<details><summary>{% endif %}
+        {% if fieldset.is_collapsible %}<details {% if 'collapse-open' in fieldset.classes %}open{% endif %}><summary>{% endif %}
         <h{{ heading_level|default:2 }} id="{{ prefix }}-{{ id_prefix}}-{{ id_suffix }}-heading" class="fieldset-heading">{{ fieldset.name }}</h{{ heading_level|default:2 }}>
         {% if fieldset.is_collapsible %}</summary>{% endif %}
     {% endif %}

docs/ref/contrib/admin/index.txt

@@ -430,7 +430,8 @@ subclass::
         space in the admin interface.
         Fieldsets with a name and the ``collapse`` style will be initially
         collapsed, using an expandable widget with a toggle for switching
-        their visibility.
+        their visibility. Add the ``collapse-open`` class to have the fieldset
+        initially expanded.
 
     * ``description``
         A string of optional extra text to be displayed at the top of each
@@ -2325,7 +2326,8 @@ The ``InlineModelAdmin`` class adds or customizes:
     A list or tuple containing extra CSS classes to apply to the fieldset that
     is rendered for the inlines. Defaults to ``None``. As with classes
     configured in :attr:`~ModelAdmin.fieldsets`, inlines with a ``collapse``
-    class will be initially collapsed using an expandable widget.
+    class will be initially collapsed using an expandable widget. Add the
+    ``collapse-open`` class to have the inline initially expanded.
 
 .. attribute:: InlineModelAdmin.extra
 

tests/admin_views/admin.py

@@ -238,6 +238,13 @@ class ArticleAdmin(ArticleAdminWithExtraUrl):
             {"classes": ("wide",), "fields": ("date", "section", "sub_section")},
         ),
         ("이름", {"fields": ("another_section",)}),
+        (
+            "Collapsible open fields",
+            {
+                "classes": ("collapse", "collapse-open"),
+                "fields": ("collapsible_open_field",),
+            },
+        ),
     )
 
     # These orderings aren't particularly useful but show that expressions can

tests/admin_views/models.py

@@ -46,6 +46,7 @@ class Article(models.Model):
     sub_section = models.ForeignKey(
         Section, models.SET_NULL, null=True, blank=True, related_name="+"
     )
+    collapsible_open_field = models.TextField(blank=True, default="")
 
     def __str__(self):
         return self.title

tests/admin_views/tests.py

@@ -6127,6 +6127,34 @@ class SeleniumTests(AdminSeleniumTestCase):
         self.assertTrue(self.selenium.find_element(By.ID, "id_title").is_displayed())
         self.take_screenshot("expanded")
 
+    @screenshot_cases(["desktop_size", "mobile_size", "dark", "high_contrast"])
+    def test_collapsible_open_fieldset(self):
+        """
+        The 'collapse-open' class in fieldsets definition allows showing
+        on load the appropriate field section.
+        """
+        from selenium.webdriver.common.by import By
+
+        self.admin_login(
+            username="super", password="secret", login_url=reverse("admin:index")
+        )
+        self.selenium.get(
+            self.live_server_url + reverse("admin:admin_views_article_add")
+        )
+        self.assertTrue(
+            self.selenium.find_element(
+                By.ID, "id_collapsible_open_field"
+            ).is_displayed()
+        )
+        self.take_screenshot("collapsible-open-expanded")
+        self.selenium.find_elements(By.TAG_NAME, "summary")[1].click()
+        self.assertFalse(
+            self.selenium.find_element(
+                By.ID, "id_collapsible_open_field"
+            ).is_displayed()
+        )
+        self.take_screenshot("collapsible-open-collapsed")
+
     @screenshot_cases(["desktop_size", "mobile_size", "rtl", "dark", "high_contrast"])
     def test_selectbox_height_collapsible_fieldset(self):
         from selenium.webdriver.common.by import By