[IMP] account_invoice_constraint_chronology: better message

The error message in case of an older conflicting invoice was not really
helpful. Now it will show the conflicting invoice name if any and also
the customer name (because a draft invoice will likely be named '/' so
just the name might not be enough). This will help the user to find
the offending invoice. It also suggest to removed the invoice date
as a possible work around.

account_invoice_constraint_chronology/model/account_move.py

@@ -34,13 +34,18 @@ def _get_older_conflicting_invoices_domain(self):
             ]
         )
 
-    def _raise_older_conflicting_invoices(self):
+    def _raise_older_conflicting_invoices(self, older_move):
         self.ensure_one()
         raise UserError(
             _(
-                "Chronology conflict: A conflicting draft invoice dated before "
-                "{date_invoice} exists, please validate it first."
-            ).format(date_invoice=format_date(self.env, self.invoice_date))
+                "Chronology conflict: A conflicting draft invoice {name} for "
+                "{partner} dated before {date_invoice} exists, please validate it "
+                "first or remove its invoice date."
+            ).format(
+                date_invoice=format_date(self.env, self.invoice_date),
+                name=older_move.name,
+                partner=older_move.partner_id.name,
+            )
         )
 
     def _get_newer_conflicting_invoices_domain(self):
@@ -174,8 +179,11 @@ def write(self, vals):
                 move._get_sequence_order_conflicting_invoices_domain(), limit=1
             ):
                 move._raise_sequence_ordering_conflict()
-            if self.search(move._get_older_conflicting_invoices_domain(), limit=1):
-                move._raise_older_conflicting_invoices()
+            older_move = self.search(
+                move._get_older_conflicting_invoices_domain(), limit=1
+            )
+            if older_move:
+                move._raise_older_conflicting_invoices(older_move)
             if move in previously_validated:
                 if self.search(
                     move._get_sequence_order_conflicting_previously_validated(), limit=1