Improve usability of account.move creation/edition

Default value for account_id, debit, credit, similar to v8 behavior

account_usability/__manifest__.py

@@ -31,6 +31,7 @@ This module has been written by Alexis de Lattre from Akretion <alexis.delattre@
     'website': 'http://www.akretion.com',
     'depends': [
         'account',
+        'base_view_inheritance_extension',
         'base_usability',  # needed only to access base_usability.group_nobody
                            # in v12, I may create a module only for group_nobody
         ],

account_usability/account.py

@@ -282,6 +282,28 @@ class AccountMove(models.Model):
     # which seems a bit lazy for me...
     ref = fields.Char(states={'posted': [('readonly', True)]})
     date = fields.Date(copy=False)
+    default_account_id = fields.Many2one(
+        related='journal_id.default_debit_account_id', readonly=True)
+    default_credit = fields.Float(
+        compute='_compute_default_credit_debit', readonly=True)
+    default_debit = fields.Float(
+        compute='_compute_default_credit_debit', readonly=True)
+
+    @api.depends('line_ids.credit', 'line_ids.debit')
+    def _compute_default_credit_debit(self):
+        for move in self:
+            total_debit = total_credit = default_debit = default_credit = 0.0
+            for l in move.line_ids:
+                total_debit += l.debit
+                total_credit += l.credit
+            # I could use float_compare, but I don't think it's really needed
+            # in this context
+            if total_debit > total_credit:
+                default_credit = total_debit - total_credit
+            else:
+                default_debit = total_credit - total_debit
+            move.default_credit = default_credit
+            move.default_debit = default_debit
 
 
 class AccountMoveLine(models.Model):

account_usability/account_view.xml

@@ -288,9 +288,15 @@ module -->
     <field name="arch" type="xml">
         <field name="ref" position="after">
             <field name="default_move_line_name"/>
+            <field name="default_account_id" invisible="1"/>
+            <field name="default_credit" invisible="0"/>
+            <field name="default_debit" invisible="0"/>
         </field>
         <xpath expr="//field[@name='line_ids']" position="attributes">
-            <attribute name="context">{'line_ids': line_ids, 'journal_id': journal_id, 'default_name': default_move_line_name}</attribute>
+            <attribute name="context" operation="python_dict" key="default_name">default_move_line_name</attribute>
+            <attribute name="context" operation="python_dict" key="default_account_id">default_account_id</attribute>
+            <attribute name="context" operation="python_dict" key="default_credit">default_credit</attribute>
+            <attribute name="context" operation="python_dict" key="default_debit">default_debit</attribute>
         </xpath>
         <xpath expr="//field[@name='line_ids']/tree/field[@name='date_maturity']" position="after">
             <field name="full_reconcile_id"/>