[REF] core: combine default_get() with first onchange()

When creating a new record, the client calls `default_get()`, completes
the returned values with `False`, and calls `onchange()` to apply the
onchange to the defaults.

Optimize the double round-trip by integrating `default_get()` inside
`onchange()` for the first call.  The method is called with an empty
list of fields, and usually no field values, except for records in a
one2many field.  In this case, `onchange()` does both steps above.

Task 2261084

1 files changed, 21 insertions, 3 deletions

diff --git a/odoo/models.py b/odoo/models.py
index d82806b6862..f3a2b4d7530 100644
--- a/odoo/models.py
+++ b/odoo/models.py
@@ -5857,6 +5857,10 @@ Fields:
                 names (in view order), or False
             :param field_onchange: dictionary mapping field names to their
                 on_change attribute
+
+            When ``field_name`` is falsy, the method first adds default values
+            to ``values``, applies onchange methods to them, and return all the
+            fields in ``field_onchange``.
         """
         # this is for tests using `Form`
         self.flush()
@@ -5869,6 +5873,8 @@ Fields:
         else:
             names = []
 
+        first_call = not names
+
         if not all(name in self._fields for name in names):
             return {}
 
@@ -5931,14 +5937,16 @@ Fields:
                     )
                 )
 
-            def diff(self, other):
+            def diff(self, other, force=False):
                 """ Return the values in ``self`` that differ from ``other``.
                     Requires record cache invalidation for correct output!
                 """
                 record = self['<record>']
                 result = {}
                 for name, subnames in self['<tree>'].items():
-                    if (name == 'id') or (other.get(name) == self[name]):
+                    if name == 'id':
+                        continue
+                    if not force and other.get(name) == self[name]:
                         continue
                     field = record._fields[name]
                     if field.type not in ('one2many', 'many2many'):
@@ -5968,6 +5976,16 @@ Fields:
 
         nametree = PrefixTree(self.browse(), field_onchange)
 
+        if first_call:
+            names = list(nametree)
+            values.update(self.default_get([
+                name
+                for name in names
+                if name not in values
+            ]))
+            for name in names:
+                values.setdefault(name, False)
+
         # prefetch x2many lines without data (for the initial snapshot)
         for name, subnames in nametree.items():
             if subnames and values.get(name):
@@ -6065,7 +6083,7 @@ Fields:
 
         # determine values that have changed by comparing snapshots
         self.invalidate_cache()
-        result['value'] = snapshot1.diff(snapshot0)
+        result['value'] = snapshot1.diff(snapshot0, force=first_call)
 
         # format warnings
         warnings = result.pop('warnings')