add feature to zero debit tax line and subtract the credit line tax when POS journal entry posted

__init__.py

@@ -1 +1,3 @@
-# -*- coding: utf-8 -*-
+# -*- coding: utf-8 -*-
+
+from . import models

models/__init__.py

@@ -0,0 +1,3 @@
+# -*- coding: utf-8 -*-
+
+from . import pos_session

models/pos_session.py

@@ -0,0 +1,124 @@
+# -*- coding: utf-8 -*-
+import logging
+from collections import defaultdict
+
+from odoo import models
+from odoo.tools.float_utils import float_is_zero, float_round
+
+_logger = logging.getLogger(__name__)
+
+
+class PosSession(models.Model):
+    _inherit = "pos.session"
+
+    def _create_account_move(self, balancing_account=False, amount_to_balance=0, bank_payment_method_diffs=None):
+        data = super()._create_account_move(
+            balancing_account=balancing_account,
+            amount_to_balance=amount_to_balance,
+            bank_payment_method_diffs=bank_payment_method_diffs,
+        )
+        self._adjust_vat_tax_lines()
+        return data
+
+    def _adjust_vat_tax_lines(self):
+        """Remove debit VAT tax lines and reduce matching credit VAT totals."""
+        for session in self:
+            move = session.move_id
+            if not move or move.state != "draft":
+                continue
+
+            tax_lines = move.line_ids.filtered(lambda l: l.display_type == "tax")
+            debit_tax_lines = tax_lines.filtered(lambda l: l.balance > 0)
+            if not debit_tax_lines:
+                continue
+
+            grouped = defaultdict(list)
+            for debit_line in debit_tax_lines:
+                key = (
+                    debit_line.account_id.id,
+                    debit_line.tax_repartition_line_id.id if debit_line.tax_repartition_line_id else None,
+                )
+                grouped[key].append(debit_line)
+
+            company_currency = move.company_currency_id
+            for key, lines_to_remove in grouped.items():
+                account_id, repartition_id = key
+                credit_candidates = tax_lines.filtered(
+                    lambda l: l not in debit_tax_lines
+                    and l.account_id.id == account_id
+                    and l.balance < 0
+                    and (not repartition_id or l.tax_repartition_line_id.id == repartition_id)
+                )
+                if not credit_candidates and repartition_id:
+                    credit_candidates = tax_lines.filtered(
+                        lambda l: l not in debit_tax_lines and l.account_id.id == account_id and l.balance < 0
+                    )
+
+                if not credit_candidates:
+                    _logger.warning(
+                        "POS session %s move %s: could not find credit VAT line to adjust for account %s.",
+                        session.name,
+                        move.name or move.ref,
+                        account_id,
+                    )
+                    continue
+
+                for debit_line in lines_to_remove:
+                    remaining_balance = debit_line.balance
+                    remaining_amount_currency = (
+                        debit_line.amount_currency if debit_line.currency_id else 0.0
+                    )
+                    for credit_line in credit_candidates:
+                        if float_is_zero(remaining_balance, precision_rounding=company_currency.rounding):
+                            break
+
+                        credit_available = -credit_line.balance
+                        consume = min(credit_available, remaining_balance)
+                        if float_is_zero(consume, precision_rounding=company_currency.rounding):
+                            continue
+
+                        proportion = consume / remaining_balance if remaining_balance else 0.0
+                        step_amount_currency = (
+                            remaining_amount_currency * proportion if credit_line.currency_id else 0.0
+                        )
+
+                        new_balance = credit_line.balance + consume
+                        if float_is_zero(new_balance, precision_rounding=company_currency.rounding):
+                            new_debit = 0.0
+                            new_credit = 0.0
+                        elif new_balance < 0:
+                            new_debit = 0.0
+                            new_credit = -new_balance
+                        else:
+                            new_debit = new_balance
+                            new_credit = 0.0
+
+                        write_vals = {
+                            "debit": float_round(new_debit, precision_rounding=company_currency.rounding),
+                            "credit": float_round(new_credit, precision_rounding=company_currency.rounding),
+                        }
+                        if credit_line.currency_id:
+                            currency = credit_line.currency_id
+                            new_amount_currency = credit_line.amount_currency + step_amount_currency
+                            write_vals["amount_currency"] = float_round(
+                                new_amount_currency, precision_rounding=currency.rounding
+                            )
+                        credit_line.with_context(check_move_validity=False).write(write_vals)
+
+                        remaining_balance -= consume
+                        if credit_line.currency_id:
+                            remaining_amount_currency -= step_amount_currency
+
+                    if not float_is_zero(remaining_balance, precision_rounding=company_currency.rounding):
+                        _logger.warning(
+                            "POS session %s move %s: VAT debit removal left unmatched balance of %s.",
+                            session.name,
+                            move.name or move.ref,
+                            remaining_balance,
+                        )
+                    zero_vals = {"debit": 0.0, "credit": 0.0}
+                    if debit_line.currency_id:
+                        zero_vals["amount_currency"] = 0.0
+                    if "tax_base_amount" in debit_line._fields:
+                        zero_vals["tax_base_amount"] = 0.0
+                    debit_line.with_context(check_move_validity=False).write(zero_vals)