Set the help_text id attribute to the field aria-describedby (#716)

Otherwise, the rendered HTML does contains an `aria-describedby` that
references a nonexistent element.

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 - Switch to just and uv for package management (#734).
 - Remove `<nav>` from pagination (#686, @xi).
+- Add an `id` to the help text of fields for Django 5.0+, to match the `aria-describedby` attribute.
 - Drop support for Python 3.8 in the test matrix
 
 ## 24.3 (2024-09-17)

src/django_bootstrap5/renderers.py

@@ -394,11 +394,14 @@ def get_help_html(self):
         """Return HTML for help text."""
         help_text = self.help_text or ""
         if help_text:
+            widget_attrs = self.field.build_widget_attrs(self.widget.attrs)
+            aria_describedby = widget_attrs.get("aria-describedby")
             return render_template_file(
                 self.field_help_text_template,
                 context={
                     "field": self.field,
                     "help_text": help_text,
+                    "id_help_text": aria_describedby,
                     "layout": self.layout,
                     "show_help": self.show_help,
                 },

src/django_bootstrap5/templates/django_bootstrap5/field_help_text.html

@@ -1 +1 @@
-{% if help_text %}<div class="form-text">{{ help_text|safe }}</div>{% endif %}
+{% if help_text %}<div {% if id_help_text %}id="{{ id_help_text }}" {% endif %}class="form-text">{{ help_text|safe }}</div>{% endif %}

tests/test_bootstrap_field.py

@@ -1,6 +1,6 @@
 from django import forms
 
-from .base import BootstrapTestCase
+from .base import DJANGO_VERSION, BootstrapTestCase
 
 
 class XssTestForm(forms.Form):
@@ -24,10 +24,21 @@ def test_illegal_field(self):
     def test_show_help(self):
         html = self.render("{% bootstrap_field form.subject %}", {"form": SubjectTestForm()})
         self.assertIn("my_help_text", html)
+        if DJANGO_VERSION >= "5":
+            self.assertIn('aria-describedby="id_subject_helptext"', html)
+            self.assertIn('<div id="id_subject_helptext" class="form-text">my_help_text</div>', html)
         self.assertNotIn("<i>my_help_text</i>", html)
         html = self.render("{% bootstrap_field form.subject show_help=False %}", {"form": SubjectTestForm()})
         self.assertNotIn("my_help_text", html)
 
+    if DJANGO_VERSION >= "5":
+
+        def test_help_text_overridden_aria_describedby(self):
+            form = SubjectTestForm()
+            form.fields["subject"].widget.attrs["aria-describedby"] = "my_id"
+            html = self.render("{% bootstrap_field form.subject %}", {"form": form})
+            self.assertIn('<div id="my_id" class="form-text">my_help_text</div>', html)
+
     def test_placeholder(self):
         html = self.render("{% bootstrap_field form.subject %}", {"form": SubjectTestForm()})
         self.assertIn('type="text"', html)

tests/test_bootstrap_form.py

@@ -38,14 +38,17 @@ def test_exclude(self):
         )
         if DJANGO_VERSION >= "5":
             html = html.replace(' aria-describedby="id_required_text_helptext"', "")
+            help_text = '<div id="id_required_text_helptext" class="form-text"><i>required_text_help</i>'
+        else:
+            help_text = '<div class="form-text"><i>required_text_help</i>'
         self.assertHTMLEqual(
             html,
             (
                 '<div class="mb-3 django_bootstrap5-req">'
                 '<label class="form-label" for="id_required_text">Required text</label>'
                 '<input type="text" name="required_text" class="form-control"'
                 ' placeholder="Required text" required id="id_required_text">'
-                '<div class="form-text"><i>required_text_help</i>'
+                f"{help_text}"
                 "</div>"
             ),
         )