[FIX] hr_contract: Exclude gaps on first contract date computation

Purpose
=======

This field is used for several things, like the simple holiday pay recovery.

Normally, we expect the HR officers to create a new employee, instead of
unarchiving the old one, but this could happen.

If someone leaves the company, and come back, take the new entry date as
first contract date instead of the original one.

closes odoo/odoo#83493

Taskid: 2745947
X-original-commit: a17c601fffca149a5c4d7be2924fb581ae408299
Related: odoo/enterprise#23790
Signed-off-by: Yannick Tivisse (yti) <yti@odoo.com>

addons/hr_contract/models/hr_employee.py

@@ -1,6 +1,7 @@
 # -*- coding: utf-8 -*-
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 
+from datetime import date
 from odoo import api, fields, models
 from odoo.osv import expression
 
@@ -22,14 +23,35 @@ class Employee(models.Model):
         self.ensure_one()
         return self.sudo().contract_ids.filtered(lambda c: c.state != 'cancel')
 
+    def _get_first_contract_date(self, no_gap=True):
+        self.ensure_one()
+        def remove_gap(contracts):
+            # We do not consider a gap of more than 4 days to be a same occupation
+            # contracts are considered to be ordered correctly
+            if not contracts:
+                return self.env['hr.contract']
+            if len(contracts) == 1:
+                return contracts
+            current_contract = contracts[0]
+            older_contracts = contracts[1:]
+            current_date = current_contract.date_start
+            for i, other_contract in enumerate(older_contracts):
+                # Consider current_contract.date_end being false as an error and cut the loop
+                gap = (current_date - (other_contract.date_end or date(2100, 1, 1))).days
+                current_date = other_contract.date_start
+                if gap >= 4:
+                    return older_contracts[0:i] + current_contract
+            return older_contracts + current_contract
+
+        contracts = self._get_first_contracts().sorted('date_start', reverse=True)
+        if no_gap:
+            contracts = remove_gap(contracts)
+        return min(contracts.mapped('date_start')) if contracts else False
+
     @api.depends('contract_ids.state', 'contract_ids.date_start')
     def _compute_first_contract_date(self):
         for employee in self:
-            contracts = employee._get_first_contracts()
-            if contracts:
-                employee.first_contract_date = min(contracts.mapped('date_start'))
-            else:
-                employee.first_contract_date = False
+            employee.first_contract_date = employee._get_first_contract_date()
 
     @api.depends('contract_id', 'contract_id.state', 'contract_id.kanban_state')
     def _compute_contract_warning(self):

addons/hr_contract/tests/test_contract.py

@@ -89,3 +89,15 @@ class TestHrContracts(TestContractCommon):
         contract = self.create_contract('draft', 'normal', date(2018, 1, 1), date(2018, 1, 2))
         contract.state = 'open'
         self.assertEqual(self.employee.contract_id, contract)
+
+    def test_first_contract_date(self):
+        self.create_contract('open', 'normal', date(2018, 1, 1), date(2018, 1, 31))
+        self.assertEqual(self.employee.first_contract_date, date(2018, 1, 1))
+
+        # New contract, no gap
+        self.create_contract('open', 'normal', date(2017, 1, 1), date(2017, 12, 31))
+        self.assertEqual(self.employee.first_contract_date, date(2017, 1, 1))
+
+        # New contract, with gap
+        self.create_contract('open', 'normal', date(2016, 1, 1), date(2016, 1, 31))
+        self.assertEqual(self.employee.first_contract_date, date(2017, 1, 1))