[FIX] gamification: goal definition for models without inherits

When attempting to define a goal
using a model that does not have any `inherits`
- which happens most the time-,
it was not possible to choose the
`Field to Sum` and the `Date Field`,
due to the domain set in the view
which is no longer working in 9.0.

The domain is no longer working because:
 - The onchange result for a one2many for which
 the value is set to `[(6, 0, [])]` is now `[]`,
 while, in 8.0, the tuple with the command `6` and the empty
 list was preserved
 - the empty list `model_inherited_model_ids` is considered as `True` by py.js,
  and therefore it fallbacks to `model_inherited_model_ids[0]`, but
  as this is an empty list, it crashes.

The solution proposed in this revision solves the issue, while
making the domain applied on these fields less fragile.

opw-658892

addons/gamification/models/goal.py

@@ -2,7 +2,7 @@
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 
 from openerp import SUPERUSER_ID
-from openerp.osv import fields, osv
+from openerp.osv import fields, osv, expression
 from openerp.tools import DEFAULT_SERVER_DATE_FORMAT as DF
 from openerp.tools.safe_eval import safe_eval
 from openerp.tools.translate import _
@@ -64,6 +64,8 @@ class gamification_goal_definition(osv.Model):
         'model_id': fields.many2one('ir.model',
             string='Model',
             help='The model object for the field to evaluate'),
+        # model_inherited_model_ids can be removed in master.
+        # It was only used to force a domain in the form view which is now set by `on_change_model_id`
         'model_inherited_model_ids': fields.related('model_id', 'inherited_model_ids', type="many2many", obj="ir.model",
             string="Inherited models", readonly="True"),
         'field_id': fields.many2one('ir.model.fields',
@@ -146,12 +148,14 @@ class gamification_goal_definition(osv.Model):
         return res
 
     def on_change_model_id(self, cr, uid, ids, model_id, context=None):
-        """Prefill field model_inherited_model_ids"""
+        """Force domain for the `field_id` and `field_date_id` fields"""
         if not model_id:
-            return {'value': {'model_inherited_model_ids': []}}
+            return {'domain': {'field_id': expression.FALSE_DOMAIN, 'field_date_id': expression.FALSE_DOMAIN}}
         model = self.pool['ir.model'].browse(cr, uid, model_id, context=context)
-        # format (6, 0, []) to construct the domain ('model_id', 'in', m and m[0] and m[0][2])
-        return {'value': {'model_inherited_model_ids': [(6, 0, [m.id for m in model.inherited_model_ids])]}}
+        model_fields_domain = ['|', ('model_id', '=', model_id), ('model_id', 'in', model.inherited_model_ids.ids)]
+        model_date_fields_domain = expression.AND([[('ttype', 'in', ('date', 'datetime'))], model_fields_domain])
+        return {'domain': {'field_id': model_fields_domain, 'field_date_id': model_date_fields_domain}}
+
 
 class gamification_goal(osv.Model):
     """Goal instance for a user

addons/gamification/views/goal.xml

@@ -246,18 +246,9 @@
                                 <!-- Hide the fields below if manually -->
                                 <field name="model_id" class="oe_inline" on_change="on_change_model_id(model_id)"
                                     attrs="{'invisible':[('computation_mode','not in',('sum', 'count'))], 'required':[('computation_mode','in',('sum', 'count'))]}"/>
-                                <field name="model_inherited_model_ids" invisible="True" />
                                 <field name="field_id" class="oe_inline"
-                                    attrs="{'invisible':[('computation_mode','!=','sum')], 'required':[('computation_mode','=','sum')]}"
-                                    domain="['|',
-                                        ('model_id', '=', model_id),
-                                        ('model_id', 'in', model_inherited_model_ids and model_inherited_model_ids[0] and model_inherited_model_ids[0][2])]" />
-                                <field name="field_date_id" class="oe_inline" attrs="{'invisible':[('computation_mode','not in',('sum', 'count'))]}"
-                                    domain="[
-                                        ('ttype', 'in', ('date', 'datetime')),
-                                        '|',
-                                            ('model_id', '=', model_id),
-                                            ('model_id', 'in', model_inherited_model_ids and model_inherited_model_ids[0] and model_inherited_model_ids[0][2])]" />
+                                    attrs="{'invisible':[('computation_mode','!=','sum')], 'required':[('computation_mode','=','sum')]}"/>
+                                <field name="field_date_id" class="oe_inline" attrs="{'invisible':[('computation_mode','not in',('sum', 'count'))]}"/>
                                 <field name="domain" attrs="{'invisible':[('computation_mode','not in',('sum', 'count'))], 'required':[('computation_mode','in',('sum', 'count'))]}" class="oe_inline"/>
                                 <field name="compute_code" attrs="{'invisible':[('computation_mode','!=','python')], 'required':[('computation_mode','=','python')]}" placeholder="e.g. result = pool.get('mail.followers').search(cr, uid, [('res_model', '=', 'mail.channel'), ('partner_id', '=', object.user_id.partner_id.id)], count=True, context=context)"/>
                                 <field name="condition" widget="radio"/>