create button force_draft and set group

payroll.py

@@ -119,6 +119,28 @@ class Payroll(metaclass=PoolMeta):
     events = fields.Function(fields.One2Many('staff.event', None,
         'Assistance'), 'get_events')
 
+    @classmethod
+    def __setup__(cls):
+        super(Payroll, cls).__setup__()
+        cls._order = [
+            ('period', 'DESC'),
+            ('start', 'DESC'),
+        ]
+        cls._transitions |= set((
+            ('draft', 'cancel'),
+            ('cancel', 'draft'),
+            ('draft', 'processed'),
+            ('processed', 'posted'),
+            ('posted', 'draft'),
+            ('processed', 'draft'),
+        ))
+        cls._buttons.update({
+            'force_draft': {
+                'invisible': Eval('state') != 'posted',
+                'depends': ['state'],
+            },
+        })
+
     @fields.depends('end', 'date_effective')
     def on_change_with_date_effective(self):
         if self.end:
@@ -891,13 +913,14 @@ class Payroll(metaclass=PoolMeta):
         return sum(res)
 
     @classmethod
+    @ModelView.button
     @Workflow.transition('draft')
-    def draft(cls, records):
+    def force_draft(cls, records):
         Move = Pool().get('account.move')
         for payroll in records:
             if payroll.move:
                 Move.draft([payroll.move.id])
-                #Move.delete([payroll.move])
+                # Move.delete([payroll.move])
 
     def send_payroll_email(self):
         pool = Pool()

payroll.xml

@@ -352,5 +352,17 @@ this repository contains the full copyright notices and license terms. -->
         <menuitem parent="staff.menu_assitants" id="menu_payroll_task"
             action="act_payroll_task_form"/>
 
+        <record model="ir.model.button" id="payroll_force_draft_button">
+            <field name="name">force_draft</field>
+            <field name="string">Force Draft</field>
+            <field name="confirm">Are you sure you want to force draft payroll posted?</field>
+            <field name="model" search="[('model', '=', 'staff.payroll')]"/>
+        </record>
+        <record model="ir.model.button-res.group"
+                id="payroll_force_draft_button_group_account">
+            <field name="button" ref="payroll_force_draft_button"/>
+            <field name="group" ref="account.group_account"/>
+        </record>
+
     </data>
 </tryton>

view/payroll_form.xml

@@ -27,4 +27,9 @@ this repository contains the full copyright notices and license terms. -->
             <field name="events" colspan="4"/>
         </page>
     </xpath>
+    <xpath expr="/form/group[@id='state_buttons']/group[@id='buttons']/button[@name='process']"
+        position="after">
+            <button name="force_draft" string="Force Draft"
+                icon="tryton-forward"/>
+    </xpath>
 </data>