From 3db3dff24ddf0c36de33a61611f9780e22903193 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?C=C3=A9dric=20Krier?= <ced@b2ck.com>
Date: Sat, 5 Sep 2020 23:37:58 +0200
Subject: [PATCH] Allow setting the tax date on taxable lines

We add a taxing date to the invoice line which allow overriding the value of
the invoice.
When crediting an invoice, the original tax date of each line is stored on the
credit line so the tax are computed the same way.

issue9520
review323791002
---
 CHANGELOG                  |  1 +
 invoice.py                 | 36 +++++++++++++++++++++---------------
 tests/scenario_invoice.rst |  6 ++++++
 view/invoice_line_form.xml |  4 ++++
 4 files changed, 32 insertions(+), 15 deletions(-)

diff --git a/CHANGELOG b/CHANGELOG
index c4d945f8e6..3838ecbd27 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,4 @@
+* Add optional taxes date on invoice line
 * Convert Invoice.update_taxes into dualmethod
 * Rename invoice state from cancel to cancelled
 
diff --git a/invoice.py b/invoice.py
index 9e1721ce66..0158f14725 100644
--- a/invoice.py
+++ b/invoice.py
@@ -820,20 +820,9 @@ class Invoice(Workflow, ModelSQL, ModelView, TaxableMixin):
     @property
     def taxable_lines(self):
         taxable_lines = []
-        # In case we're called from an on_change we have to use some sensible
-        # defaults
         for line in self.lines:
-            if getattr(line, 'type', None) != 'line':
-                continue
-            taxable_lines.append(tuple())
-            for attribute, default_value in [
-                    ('taxes', []),
-                    ('unit_price', Decimal(0)),
-                    ('quantity', 0.),
-                    ]:
-                value = getattr(line, attribute, None)
-                taxable_lines[-1] += (
-                    value if value is not None else default_value,)
+            if getattr(line, 'type', None) == 'line':
+                taxable_lines.extend(line.taxable_lines)
         return taxable_lines
 
     @property
@@ -1744,6 +1733,15 @@ class InvoiceLine(sequence_ordered(), ModelSQL, ModelView, TaxableMixin):
             'readonly': _states['readonly'] | ~Bool(Eval('account')),
             },
         depends=['type', 'invoice_type', 'company', 'account'] + _depends)
+    taxes_date = fields.Date(
+        "Taxes Date",
+        states={
+            'invisible': Eval('type') != 'line',
+            'readonly': _states['readonly'],
+            },
+        depends=['type'] + _depends,
+        help="The date at which the taxes are computed.\n"
+        "Leave empty for the accounting date.")
     invoice_taxes = fields.Function(fields.Many2Many('account.invoice.tax',
         None, None, 'Invoice Taxes'), 'get_invoice_taxes')
     origin = fields.Reference('Origin', selection='get_origin', select=True,
@@ -1920,11 +1918,18 @@ class InvoiceLine(sequence_ordered(), ModelSQL, ModelView, TaxableMixin):
 
     @property
     def taxable_lines(self):
-        return [(self.taxes, self.unit_price, self.quantity)]
+        # In case we're called from an on_change we have to use some sensible
+        # defaults
+        return [(
+                getattr(self, 'taxes', None) or [],
+                getattr(self, 'unit_price', None) or Decimal(0),
+                getattr(self, 'quantity', None) or 0,
+                getattr(self, 'tax_date', None),
+                )]
 
     @property
     def tax_date(self):
-        return self.invoice.tax_date
+        return self.taxes_date or self.invoice.tax_date
 
     def _get_tax_context(self):
         if self.invoice:
@@ -2254,6 +2259,7 @@ class InvoiceLine(sequence_ordered(), ModelSQL, ModelView, TaxableMixin):
         for field in ('sequence', 'type', 'invoice_type', 'unit_price',
                 'description', 'unit', 'product', 'account'):
             setattr(line, field, getattr(self, field))
+        line.taxes_date = self.tax_date
         line.taxes = self.taxes
         return line
 
diff --git a/tests/scenario_invoice.rst b/tests/scenario_invoice.rst
index 5dab753670..dcab12c817 100644
--- a/tests/scenario_invoice.rst
+++ b/tests/scenario_invoice.rst
@@ -220,6 +220,12 @@ Credit invoice with refund::
     'cancelled'
     >>> invoice.reconciled == today
     True
+    >>> credit_note, = Invoice.find([
+    ...     ('type', '=', 'out'), ('id', '!=', invoice.id)])
+    >>> credit_note.state
+    'paid'
+    >>> all(line.taxes_date == today for line in credit_note.lines)
+    True
     >>> receivable.reload()
     >>> receivable.debit
     Decimal('240.00')
diff --git a/view/invoice_line_form.xml b/view/invoice_line_form.xml
index 5b37712d19..4ecddb1025 100644
--- a/view/invoice_line_form.xml
+++ b/view/invoice_line_form.xml
@@ -23,6 +23,10 @@ this repository contains the full copyright notices and license terms. -->
             <label name="amount"/>
             <field name="amount"/>
             <field name="taxes" colspan="4"/>
+            <label name="taxes_date"/>
+            <field name="taxes_date"/>
+            <newline/>
+
             <label name="origin"/>
             <field name="origin" colspan="3"/>
         </page>