[FIX] Preserve analytic account on tax lines which are on same general account as invoice line

After careful analysis, I'm now convinced it is a good thing to preserve
the analytic account on taxes line which have the same general account
as the invoice line.

This is the best default case and will save time for users,
while leaving the flexibility to adapt the analytic account on
taxes manually.

addons/account/account_invoice.py

@@ -145,7 +145,7 @@ class account_invoice(models.Model):
             else:
                 self.residual = new_value
         # prevent the residual amount on the invoice to be less than 0
-        self.residual = max(self.residual, 0.0)            
+        self.residual = max(self.residual, 0.0)
 
     @api.one
     @api.depends(
@@ -1549,6 +1549,14 @@ class account_invoice_tax(models.Model):
                     val['account_id'] = tax['account_paid_id'] or line.account_id.id
                     val['account_analytic_id'] = tax['account_analytic_paid_id']
 
+                # If the taxes generate moves on the same financial account as the invoice line
+                # and no default analytic account is defined at the tax level, propagate the
+                # analytic account from the invoice line to the tax line. This is necessary
+                # in situations were (part of) the taxes cannot be reclaimed,
+                # to ensure the tax move is allocated to the proper analytic account.
+                if not val.get('account_analytic_id') and line.account_analytic_id and val['account_id'] == line.account_id.id:
+                    val['account_analytic_id'] = line.account_analytic_id.id
+
                 key = (val['tax_code_id'], val['base_code_id'], val['account_id'])
                 if not key in tax_grouped:
                     tax_grouped[key] = val