[IMP] - get default values for non record onchange call

other improvement:

set onchange_specs to all fields as _onchange_spec()
retrun onchange fields for default view
return field value if it's set in onchange_fields (usuful to get default value for a field)

onchange_helper/models/base.py

@@ -22,9 +22,12 @@ class Base(models.AbstractModel):
 
     @api.model
     def play_onchanges(self, values, onchange_fields):
-        onchange_specs = self._onchange_spec()
+        # _onchange_spec() will return onchange fields from the default view
         # we need all fields in the dict even the empty ones
         # otherwise 'onchange()' will not apply changes to them
+        onchange_specs = {
+            field_name: '1' for field_name, field in self._fields.items()
+        }
         all_values = values.copy()
         # If self is a record (play onchange on existing record)
         # we take the value of the field
@@ -38,7 +41,8 @@ class Base(models.AbstractModel):
                 }
             )
         else:
-            record_values = {}
+            # We get default values, they may be used in onchange
+            record_values = self.default_get(self._fields.keys())
         for field in self._fields:
             if field not in all_values:
                 all_values[field] = record_values.get(field, False)
@@ -52,5 +56,6 @@ class Base(models.AbstractModel):
         return {
             f: v
             for f, v in all_values.items()
-            if not self._fields[f].compute and (f in values or f in new_values)
+            if not self._fields[f].compute
+            and (f in values or f in new_values or f in onchange_fields)
         }

onchange_helper/readme/CONTRIBUTORS.rst

@@ -1,3 +1,4 @@
 * Guewen Baconnier <guewen.baconnier@camptocamp.com>
 * Florian da Costa <florian.dacosta@akretion.com>
 * Andrea Stirpe <a.stirpe@onestein.nl>
+* Souheil Bejaoui <souheil.bejaoui@acsone.eu>

onchange_helper/readme/USAGE.rst

@@ -11,6 +11,17 @@ Example if you want to create a sale order and you want to get the values relati
 
 Then, `vals` will be updated with partner_invoice_id, partner_shipping_id, pricelist_id, etc...
 
+Default values will be used to process onchange methods, if respective fields are not set in `vals`.
+You can get them if you pass fields name in the list of fields.
+
+
+    `vals = {'partner_id': 1}`
+
+    `vals = self.env['sale.order'].play_onchanges(vals, ['partner_id', 'date_order'])`
+
+`vals` will contain, in addition to the changed values, the default value for `date_order`
+
+
 You can also use it on existing record for example:
 
      `vals = {'partner_shipping_id': 1}`