fix(change_request): hide Head role on Add Member when the group already has one (#871)

A group can have at most one Head of Household, so the Head role is now
removed from the Role options when the target group already has an active
head. Implemented as a computed allowed_role_ids driving the Role field
domain (UI restriction only; head-of-household configurability stays with
#1006).

Author: emjay0921

spp_change_request_v2/details/add_member.py

@@ -135,6 +135,13 @@ class SPPCRDetailAddMember(models.Model):
         string="Has Membership Roles",
         help="True when the urn:openspp:vocab:group-membership-type vocabulary has any active code.",
     )
+    allowed_role_ids = fields.Many2many(
+        "spp.vocabulary.code",
+        string="Allowed Roles",
+        compute="_compute_allowed_role_ids",
+        help="Roles selectable for the new member; the Head role is excluded when "
+        "the group already has a Head of Household (OP#871).",
+    )
 
     # ──────────────────────────────────────────────────────────────────────
     # Read-only context: existing members of the group (for the spec's
@@ -202,3 +209,28 @@ def _compute_existing_memberships(self):
                 rec.existing_membership_ids = Membership.search([("group", "=", group.id), ("status", "=", "active")])
             else:
                 rec.existing_membership_ids = Membership.browse([])
+
+    @api.depends("change_request_id", "change_request_id.registrant_id")
+    def _compute_allowed_role_ids(self):
+        """Restrict the Role selection: a group can have only one Head, so the
+        Head role is removed from the options when the target group already has
+        an active Head of Household (OP#871)."""
+        Code = self.env["spp.vocabulary.code"]
+        Membership = self.env["spp.group.membership"]
+        all_roles = Code.search([("vocabulary_id.namespace_uri", "=", "urn:openspp:vocab:group-membership-type")])
+        for rec in self:
+            roles = all_roles
+            group = rec.change_request_id.registrant_id
+            if group and group.is_group:
+                group_has_head = bool(
+                    Membership.search_count(
+                        [
+                            ("group", "=", group.id),
+                            ("status", "=", "active"),
+                            ("membership_type_ids.code", "=", "head"),
+                        ]
+                    )
+                )
+                if group_has_head:
+                    roles = all_roles.filtered(lambda r: r.code != "head")
+            rec.allowed_role_ids = roles

spp_change_request_v2/tests/test_add_member_strategy.py

@@ -263,6 +263,35 @@ def test_preview_shows_fields_and_tables(self):
         self.assertIn("Occupation", html)
         self.assertNotIn("phone_count", html)
 
+    def test_allowed_roles_excludes_head_when_group_has_head(self):
+        """OP#871: the Head role is removed from the Role options when the group
+        already has an active Head of Household; otherwise all roles are allowed."""
+        # Group without a head -> Head is selectable.
+        no_head_codes = set(
+            self._make_cr(given_name="A", family_name="B").get_detail().allowed_role_ids.mapped("code")
+        )
+        self.assertIn("head", no_head_codes)
+
+        # Group with an active head -> Head removed; every other role preserved.
+        head_indiv = self.partner_model.create({"name": "Head Person", "is_registrant": True, "is_group": False})
+        group_with_head = self.partner_model.create(
+            {"name": "Group With Head", "is_registrant": True, "is_group": True}
+        )
+        self.membership_model.create(
+            {
+                "group": group_with_head.id,
+                "individual": head_indiv.id,
+                "membership_type_ids": [Command.link(self.head_kind.id)],
+            }
+        )
+        with_head_codes = set(
+            self._make_cr(registrant=group_with_head, given_name="C", family_name="D")
+            .get_detail()
+            .allowed_role_ids.mapped("code")
+        )
+        self.assertNotIn("head", with_head_codes)
+        self.assertEqual(with_head_codes, no_head_codes - {"head"})
+
     def test_add_member_writes_single_address(self):
         """The single Address field maps to the registry's res.partner.address
         on apply, matching how the registry stores it (OP#871 QA round 1)."""

spp_change_request_v2/views/detail_add_member_views.xml

@@ -12,6 +12,7 @@
                     <field name="is_cr_manager" invisible="1" />
                     <field name="type_requires_head" invisible="1" />
                     <field name="roles_available" invisible="1" />
+                    <field name="allowed_role_ids" invisible="1" />
                     <button
                         name="action_next_documents"
                         string="Next: Upload Documents"
@@ -160,6 +161,7 @@
                                     <field
                                         name="membership_type_id"
                                         options="{'no_create': True, 'no_open': True}"
+                                        domain="[('id', 'in', allowed_role_ids)]"
                                         required="type_requires_head"
                                     />
                                 </group>