[IMP] contract: Allow to set a manual currency

Done through an extra field + inverse in the existing compute. This way, we have
the flexibility of auto-remove custom value if it matches the computed one + we don't
need extra changes in the rest of the code.

contract/models/contract.py

@@ -34,8 +34,12 @@ class ContractContract(models.Model):
     )
     currency_id = fields.Many2one(
         compute="_compute_currency_id",
+        inverse="_inverse_currency_id",
         comodel_name="res.currency",
         string="Currency",
+    )
+    manual_currency_id = fields.Many2one(
+        comodel_name="res.currency",
         readonly=True,
     )
     contract_template_id = fields.Many2one(
@@ -149,24 +153,47 @@ class ContractContract(models.Model):
         )
         return invoices
 
-    @api.depends("pricelist_id", "partner_id", "journal_id", "company_id")
-    def _compute_currency_id(self):
-        for rec in self:
+    def _get_computed_currency(self):
+        """Helper method for returning the theoretical computed currency."""
+        self.ensure_one()
         currency = self.env['res.currency']
-            if any(rec.contract_line_ids.mapped('automatic_price')):
+        if any(self.contract_line_ids.mapped('automatic_price')):
             # Use pricelist currency
             currency = (
-                    rec.pricelist_id.currency_id or
-                    rec.partner_id.with_context(
-                        force_company=rec.company_id.id,
+                self.pricelist_id.currency_id or
+                self.partner_id.with_context(
+                    force_company=self.company_id.id,
                 ).property_product_pricelist.currency_id
             )
-            rec.currency_id = (
-                currency.id or
-                rec.journal_id.currency_id.id or
-                rec.company_id.currency_id.id
+        return (
+            currency or self.journal_id.currency_id or
+            self.company_id.currency_id
         )
 
+    @api.depends(
+        "manual_currency_id",
+        "pricelist_id",
+        "partner_id",
+        "journal_id",
+        "company_id",
+    )
+    def _compute_currency_id(self):
+        for rec in self:
+            if rec.manual_currency_id:
+                rec.currency_id = rec.manual_currency_id
+            else:
+                rec.currency_id = rec._get_computed_currency()
+
+    def _inverse_currency_id(self):
+        """If the currency is different from the computed one, then save it
+        in the manual field.
+        """
+        for rec in self:
+            if rec._get_computed_currency() != rec.currency_id:
+                rec.manual_currency_id = rec.currency_id
+            else:
+                rec.manual_currency_id = False
+
     @api.multi
     def _compute_invoice_count(self):
         for rec in self:

contract/tests/test_contract.py

@@ -2512,3 +2512,39 @@ class TestContract(TestContractBase):
                 'terminate_comment',
                 to_date('2018-02-13'),
             )
+
+    def test_currency(self):
+        currency_eur = self.env.ref("base.EUR")
+        currency_cad = self.env.ref("base.CAD")
+        # Get currency from company
+        self.contract2.journal_id = False
+        self.assertEqual(
+            self.contract2.currency_id, self.contract2.company_id.currency_id)
+        # Get currency from journal
+        journal = self.env["account.journal"].create({
+            "name": "Test journal CAD",
+            "code": "TCAD",
+            "type": "sale",
+            "currency_id": currency_cad.id,
+        })
+        self.contract2.journal_id = journal.id
+        self.assertEqual(self.contract2.currency_id, currency_cad)
+        # Get currency from contract pricelist
+        pricelist = self.env['product.pricelist'].create({
+            "name": "Test pricelist",
+            "currency_id": currency_eur.id,
+        })
+        self.contract2.pricelist_id = pricelist.id
+        self.contract2.contract_line_ids.automatic_price = True
+        self.assertEqual(self.contract2.currency_id, currency_eur)
+        # Get currency from partner pricelist
+        self.contract2.pricelist_id = False
+        self.contract2.partner_id.property_product_pricelist = pricelist.id
+        pricelist.currency_id = currency_cad.id
+        self.assertEqual(self.contract2.currency_id, currency_cad)
+        # Assign manual currency
+        self.contract2.manual_currency_id = currency_eur.id
+        self.assertEqual(self.contract2.currency_id, currency_eur)
+        # Assign same currency as computed one
+        self.contract2.currency_id = currency_cad.id
+        self.assertFalse(self.contract2.manual_currency_id)