[FIX] base_vat: compute vies_valid on create() without a write()

[kukor-odoo]

Description

Steps to Reproduce

1. Install Belgium Localization, then go to Settings → Accounting/Invoicing.
2. Enable Verify VAT Numbers (vat_check_vies).
3. Go to Accounting → Configuration → Fiscal Positions and confirm or create an Intra-Community fiscal position with:
   • Detect Automatically (auto_apply): enabled
   • VAT Required (vat_required): enabled
   • Country Group: EU, no specific country configured
4. Open an incognito/private browser window and make sure the session is unauthenticated.
5. Go to the website's /shop page and add any product to the cart.
6. Proceed to checkout until reaching the Address step (/shop/address).
7. Enter a delivery address in an EU country different from the company's country (e.g. company in Belgium, delivery address in the Netherlands).
8. In the VAT Number field, enter a real, valid, VIES-registered VAT number corresponding to the delivery country (e.g. a valid NL VAT number for a Netherlands address).
9. Click Save Address / Continue and proceed to the Payment step (/shop/payment).
10. Check the tax applied to the delivery line and the resulting order total.

Issue

The delivery product and the overall order are taxed at the standard/domestic VAT rate instead of the expected 0% intra-community rate — even though the customer provided a valid, VIES-registered EU VAT number matching the delivery country.

Root Cause

In base_vat, res.partner.create() unconditionally removes vies_valid from the ORM's pending computation queue via env.remove_to_compute(), relying on a subsequent write() to trigger the actual VIES check. This holds for the standard backend flow, where creation is followed by a write() — but the website guest checkout flow differs:

• website_sale creates the guest partner through _create_new_address().
• The partner is created via a single create() call, with no follow-up write().
• _compute_vies_valid() is therefore never triggered.
• vies_valid remains permanently unset (NULL), despite a VAT number being provided.

Downstream, account.fiscal.position._get_vat_required_valid() reads this unset value as falsy, so the Intra-Community fiscal position's vat_required condition fails and is rejected in favor of another applicable position (e.g. EU B2C or Domestic).

Solution

After partner creation, explicitly trigger _compute_vies_valid() when the partner has a VAT number and the operation is not part of a file import (import_file context) — performing the VIES check immediately instead of relying on a write() that guest checkout never issues.

Result

Guest customers providing a valid EU VAT number now get vies_valid computed immediately at creation. Fiscal position detection correctly identifies the Intra-Community position, and the expected 0% VAT treatment is applied to the delivery and order.

OPW: 6522992

[robodoo]

[FlorianGilbert]

@robodoo r+