Fix missing release field on admin interface

- Force SQLAlcheny relationships init before rendering the form
- Add tests covering this problem

Fixes #279

Assisted-by: Claude Code

blockerbugs/controllers/admin/__init__.py

@@ -25,6 +25,7 @@ import logging
 from flask import flash
 from flask_admin.babel import gettext
 import flask_admin
+from sqlalchemy.orm import configure_mappers
 from blockerbugs import app, db
 from blockerbugs.models.release import Release
 from blockerbugs.models.milestone import Milestone
@@ -97,5 +98,10 @@ class MilestoneView(FasAuthModelView):
         return True
 
 
+# Force SQLAlchemy to resolve all Mapped[] forward references and back_populates linkages
+# before Flask-Admin introspects models to scaffold forms. Without this, relationship
+# fields (e.g. Milestone.release) are silently omitted, causing AttributeErrors on submit.
+configure_mappers()
+
 admin.add_view(MilestoneView(Milestone, db.session))
 admin.add_view(ReleaseView(Release, db.session))

testing/unit/test_admin.py

@@ -0,0 +1,64 @@
+"""Tests for the admin interface"""
+
+import pytest
+from wtforms.fields.core import UnboundField
+
+from blockerbugs.controllers.admin import admin
+
+
+def _get_admin_view(model_name):
+    """Look up a Flask-Admin ModelView by its model class name."""
+    for view in admin._views:
+        if hasattr(view, "model") and view.model.__name__ == model_name:
+            return view
+    raise AssertionError(f"{model_name} view not found in admin views")
+
+
+def _get_form_field_names(model_name):
+    """Return the set of field names that Flask-Admin scaffolds for a model."""
+    view = _get_admin_view(model_name)
+    form_class = view.scaffold_form()
+    return {name for name in dir(form_class) if isinstance(getattr(form_class, name), UnboundField)}
+
+
+class TestAdminForms:
+    """Test that Flask-Admin generates the correct form fields for each model.
+
+    Flask-Admin auto-scaffolds form fields by introspecting the SQLAlchemy model.
+    With SQLAlchemy 2.0's deferred relationship initialization, relationship fields
+    (like 'release') can be silently dropped if configure_mappers() hasn't been
+    called before Flask-Admin scaffolds the form. These tests guard against that
+    regression.
+    """
+
+    @pytest.mark.parametrize(
+        "model_name, required_fields",
+        [
+            (
+                "Milestone",
+                {
+                    "release",
+                    "version",
+                    "blocker_tracker",
+                    "fe_tracker",
+                    "name",
+                    "active",
+                    "current",
+                    "succeeded_by",
+                },
+            ),
+            ("Release", {"number", "active"}),
+        ],
+    )
+    def test_form_has_all_required_fields(self, model_name, required_fields):
+        """The admin form must include all fields used by create_model().
+
+        Each ModelView.create_model() accesses specific form fields when creating
+        a new instance through the admin interface. If any are missing, form
+        submission will fail with an AttributeError.
+        """
+        fields = _get_form_field_names(model_name)
+        missing = required_fields - fields
+        assert not missing, (
+            f"{model_name} admin form is missing fields required by create_model(): {missing}"
+        )