[18.0]l10n_it_vat_settlement_communication: "identifier already exists" error on save

[micheledic]

Module

l10n_it_vat_settlement_communication

Describe the bug

Saving a comunicazione.liquidazione raises
ValidationError: Communication with identifier N already exists
even when no record with that identifier is visible to the user. The
error fires on single-company databases and with a single company
selected in the top-right switcher.

Two defects combine.

1. _get_identificativo default

The default returns count(records) + 1. Row counting does not produce
unique values. A deleted row, a gap, or an out-of-order import lets
the default land on an identifier that already exists.

2. _check_identificativo constraint scope

The Python constraint searches without a company_id filter

To Reproduce

Affected versions: 18.0 (module 18.0.1.0.1)

Steps to reproduce the behavior:

1. Create three comunicazione.liquidazione records on one company.
   The default assigns identifiers 1, 2, 3.
2. Delete the record with identifier 2.
3. Create a new record. The default returns 2 + 1 = 3, the save
   fails with
   ValidationError: Communication with identifier 3 already exists.

Expected behavior

The default returns a value that does not collide with an existing
record. The uniqueness check matches records on the same company only.

• 18.0 [18.0][FIX] l10n_it_vat_settlement_communication: fix for check_identificativo in multi-company #5194
• 19.0 [19.0][MIG] l10n_it_vat_settlement_communication: Migration to 19.0 #5092