Update sign of amount line paid according to invoice type and payment kind

Closes #14070

modules/account_payment/account.py

@@ -776,9 +776,15 @@ class Invoice(metaclass=PoolMeta):
                             continue
                         payment_amount = Decimal(0)
                         for payment in line.payments:
+                            amount_line_paid = payment.amount_line_paid
+                            if ((invoice.type == 'in'
+                                    and payment.kind == 'receivable')
+                                    or (invoice.type == 'out'
+                                        and payment.kind == 'payable')):
+                                amount_line_paid *= -1
                             with Transaction().set_context(date=payment.date):
                                 payment_amount += Currency.compute(
-                                    payment.currency, payment.amount_line_paid,
+                                    payment.currency, amount_line_paid,
                                     invoice.currency)
                         amounts[invoice.id] -= payment_amount
         return amounts

modules/account_payment/tests/scenario_account_payment_credit_note_in.rst

@@ -0,0 +1,77 @@
+=====================================
+Supplier Credit Note Payment Scenario
+=====================================
+
+Imports::
+
+    >>> from decimal import Decimal
+
+    >>> from proteus import Model, Wizard
+    >>> from trytond.modules.account.tests.tools import (
+    ...     create_chart, create_fiscalyear, get_accounts)
+    >>> from trytond.modules.account_invoice.tests.tools import (
+    ...     set_fiscalyear_invoice_sequences)
+    >>> from trytond.modules.company.tests.tools import create_company
+    >>> from trytond.tests.tools import activate_modules
+
+Activate modules::
+
+    >>> config = activate_modules(
+    ...     ['account_payment', 'account_invoice'], create_company, create_chart)
+
+    >>> Invoice = Model.get('account.invoice')
+    >>> Party = Model.get('party.party')
+    >>> Payment = Model.get('account.payment')
+    >>> PaymentJournal = Model.get('account.payment.journal')
+
+Create fiscal year::
+
+    >>> fiscalyear = set_fiscalyear_invoice_sequences(create_fiscalyear())
+    >>> fiscalyear.click('create_period')
+
+Get accounts::
+
+    >>> accounts = get_accounts()
+
+Create payment journal::
+
+    >>> payment_journal = PaymentJournal(name="Manual", process_method='manual')
+    >>> payment_journal.save()
+
+Create party::
+
+    >>> party = Party(name="Supplier")
+    >>> party.save()
+
+Create invoice::
+
+    >>> invoice = Invoice(type='in')
+    >>> invoice.party = party
+    >>> invoice.invoice_date = fiscalyear.start_date
+    >>> line = invoice.lines.new()
+    >>> line.account = accounts['expense']
+    >>> line.quantity = -1
+    >>> line.unit_price = Decimal('100')
+    >>> invoice.click('post')
+    >>> invoice.state
+    'posted'
+    >>> invoice.amount_to_pay
+    Decimal('-100.00')
+    >>> line_to_pay, = invoice.lines_to_pay
+
+Partially receive payment::
+
+    >>> pay_line = Wizard('account.move.line.pay', [line_to_pay])
+    >>> pay_line.execute('next_')
+    >>> pay_line.execute('next_')
+    >>> payment, = Payment.find()
+    >>> payment.kind
+    'receivable'
+    >>> payment.amount = Decimal('20')
+    >>> payment.click('submit')
+
+Check amount to pay::
+
+    >>> invoice.reload()
+    >>> invoice.amount_to_pay
+    Decimal('-80.00')