[FIX] hr_expense: allow to create expenses via alias for employees not related to a user

Current behavior:
When trying to create an expense using alias, if a `hr.employee` not linked to a user want to, he won't be able

This bug occurs after this [commit](https://github.com/odoo/odoo/commit/fbeb7aebcadbe77ff7774b538550373650b329fe)

Steps to reproduce the error :
- Create an employee not related to a user
- Configure alias for expenses
- Try to send an email to the expense's alias and check at the logs

After this commit:
Employees without a related user will be able to create an expense from an email alias

opw-3892778
opw-3892701
opw-3893319
opw-3893591

closes odoo/odoo#163672

X-original-commit: 1dd67119c27d219eac2b726ef88cc4af3bed2814
Signed-off-by: Brice Bartoletti (bib) <bib@odoo.com>

addons/hr_expense/models/hr_expense.py

@@ -920,14 +920,9 @@ class HrExpense(models.Model):
     @api.model
     def message_new(self, msg_dict, custom_values=None):
         email_address = email_split(msg_dict.get('email_from', False))[0]
+        employee = self._get_employee_from_email(email_address)
 
-        employee = self.env['hr.employee'].search([
-            '|',
-            ('work_email', 'ilike', email_address),
-            ('user_id.email', 'ilike', email_address)
-        ]).filtered(lambda e: e.company_id == e.user_id.company_id)
-
-        if len(employee) != 1:
+        if not employee:
             return super().message_new(msg_dict, custom_values=custom_values)
 
         expense_description = msg_dict.get('subject', '')
@@ -967,6 +962,29 @@ class HrExpense(models.Model):
         self._send_expense_success_mail(msg_dict, expense)
         return expense
 
+    @api.model
+    def _get_employee_from_email(self, email_address):
+        employee = self.env['hr.employee'].search([
+            ('user_id', '!=', False),
+            '|',
+            ('work_email', 'ilike', email_address),
+            ('user_id.email', 'ilike', email_address),
+        ])
+
+        if len(employee) > 1:
+            # Several employees can be linked to the same user.
+            # In that case, we only keep the employee that matched the user's company.
+            return employee.filtered(lambda e: e.company_id == e.user_id.company_id)
+
+        if not employee:
+            # An employee does not always have a user.
+            return self.env['hr.employee'].search([
+                ('user_id', '=', False),
+                ('work_email', 'ilike', email_address),
+            ], limit=1)
+
+        return employee
+
     @api.model
     def _parse_product(self, expense_description):
         """

addons/hr_expense/tests/test_expenses_mail_import.py

@@ -67,6 +67,43 @@ class TestExpensesMailImport(TestExpenseCommon):
             'employee_id': company_2_employee.id,
         }])
 
+    def test_import_expense_from_email_employee_without_user(self):
+        """When an employee is not linked to a user, he has to be able to create expenses from email"""
+        employee = self.expense_employee
+        employee.user_id = False
+
+        message_parsed = {
+            'message_id': "the-world-is-a-ghetto",
+            'subject': 'New expense',
+            'email_from': employee.work_email,
+            'to': 'catchall@yourcompany.com',
+            'body': "Don't you know, that for me, and for you",
+            'attachments': [],
+        }
+
+        expense = self.env['hr.expense'].message_new(message_parsed)
+        self.assertRecordValues(expense, [{
+            'employee_id': employee.id,
+        }])
+
+    def test_import_expense_from_email_no_product(self):
+        message_parsed = {
+            'message_id': "the-world-is-a-ghetto",
+            'subject': 'no product code 800',
+            'email_from': self.expense_user_employee.email,
+            'to': 'catchall@yourcompany.com',
+            'body': "Don't you know, that for me, and for you",
+            'attachments': [],
+        }
+
+        expense = self.env['hr.expense'].message_new(message_parsed)
+
+        self.assertRecordValues(expense, [{
+            'product_id': False,
+            'total_amount': 800.0,
+            'employee_id': self.expense_employee.id,
+        }])
+
     def test_import_expense_from_mail_parsing_subjects(self):
         def assertParsedValues(subject, currencies, exp_description, exp_amount, exp_product, exp_currency):
             product, amount, currency_id, description = self.env['hr.expense'] \