I created a custom module called recruit ink that I wanted to put on top of the recruitment module, it's like a recruitment request process to start the actual recruitment. In it I have a Many2one field called requested_job_id in my form view that you fill to ask for a job

What I wanted to happen is when the job field is populated a tree view in a notebook page gets filled with employees of that job but as I tried to implement this I failed over and over again sometimes the employee record just gets deleted and I have no idea why.

I also tried Many2many and creating a rel table but its the same thing as soon as I save it's getting deleted.

Here is my code module code:

from markupsafe import Markup

from odoo import api, models, fields , _
from odoo.exceptions import ValidationError, UserError


class RecruitInkDemande(models.Model):
    _name = "recruit_ink.demande"
    _description = "Demande de recrutement"
    _rec_name = "reference"
    _inherit = ["mail.thread"]


    reference = fields.Char(string="Référence" ,copy=False, readonly=True,index='trigram',default=lambda self: _('Nouveau'))
    recruitment_topic = fields.Char(string="Sujet de recrutement", required=True,tracking=True)
    expected_employees = fields.Char(string="Employé attendu",tracking=True,required=True)
    user_group = fields.Char(string="Current User", compute="_compute_check_user_group",store=False)
    requester_id = fields.Many2one('res.users',string="Demandeur", required=True,readonly=False,default= lambda self : self.env.user)
    departement_id = fields.Many2one('hr.department', string="Département", required=True, readonly=False,default=lambda self: self.env.user.department_id)
    requested_job_id = fields.Many2one(comodel_name='hr.job', string="Poste demandé", tracking=True)
    
    employee_ids = fields.One2many('hr.employee', 'demande_id', string="Employees",readonly=True)



    submission_date = fields.Datetime(string="Date de soumission", readonly=True, tracking=True)
    job_description = fields.Html(string="Déscription du poste", required=True)
    requirements = fields.Html(string="Exigences", required=True)
    update_job_description_requirements = fields.Boolean(string="",default=False,help="Cochez cette case pour mettre à jour la description et les requirements lors du choix du poste")
    status = fields.Selection([
        ('brouillon', 'BROUILLON'),
        ('en_attente', 'EN ATTENTE'),
        ('validé', 'VALIDÉ'),
        ('en_recrutement', 'EN RECRUTEMENT'),
        ('rejeté', 'REJETÉ'),
        ('cloturé', 'CLOTURÉ')
    ], string="status", default='brouillon', tracking=True)





    @api.onchange('requested_job_id')
    def _onchange_requested_job_id(self):
        for record in self:
            if record.update_job_description_requirements:
                if record.requested_job_id:
                    record.job_description = record.requested_job_id.description
                    record.requirements = record.requested_job_id.requirements

                else:
                    # Clear the fields if no requested_job_id is selected
                    record.job_description = False
                    record.requirements = False

            if record.requested_job_id:
                record.employee_ids = self.env["hr.employee"].search([("job_id", "=", record.requested_job_id.id)])
            else:
                record.employee_ids = False





    @api.ondelete(at_uninstall=False)
    def _unlink_if_brouillon(self):
        for record in self:
            if record.status != 'brouillon' and self.env.user.name !='Administrator':
                raise ValidationError("Vous ne pouvez pas supprimer les demandes qui ne sont pas dans l'état 'brouillon'.\nVous êtes pas l'administrateur ")
    def _compute_check_user_group(self):
        user=self.env.user
        if user.has_group('hr_recruitment.group_hr_recruitment_manager'):
            self.user_group = "Administrator"
        elif user.has_group('hr_recruitment.group_hr_recruitment_user'):
            self.user_group = "RH"
        elif user.has_group('hr_recruitment.group_hr_recruitment_interviewer'):
            self.user_group = "Interviewer"

    @api.model
    def get_email_to(self):
        # Retrieve the recruitment user group and the manager group
        user_group = self.env.ref("hr_recruitment.group_hr_recruitment_user")
        manager_group = self.env.ref("hr_recruitment.group_hr_recruitment_manager")
        # Filter users who belong to the user group, not the manager group, and have a valid email
        email_list = [
            usr.partner_id.email for usr in user_group.users
            if usr.partner_id.email and manager_group not in usr.groups_id
        ]
        # Join the emails into a comma-separated string
        return ",".join(email_list)




    # Workflow buttons
    def action_submit(self):
        for record in self:
            if record.status == 'brouillon':
                record.status = 'en_attente'
                record.submission_date = fields.Datetime.now()
                if record.requester_id == self.env.user:
                    self.env.ref('recruit_ink.soumission_email_template').send_mail(record.id)
    def action_validate(self):
        for record in self:
            if record.status == 'en_attente' :
                if record.requested_job_id:
                    record.status = 'validé'
                else:
                    raise ValidationError("Veuillez choisir un poste de travail valide ")
    def action_reject(self):
        for record in self:
            if record.status == 'en_attente':
                record.status = 'rejeté'
    def action_reset(self):
        for record in self:
            if record.status == 'en_attente':
                record.status = 'brouillon'
    def action_recruit(self):
        for record in self:
            if record.status =='validé':
                record.status = 'en_recrutement'








    def action_close(self):
        for record in self:
            if record.status in ['validé', 'en_recrutement']:
                record.status = 'cloturé'

    #smart buttons
    def action_open_job_configuration(self):
        self.ensure_one()  # Ensure only one record is being processed
        if self.requested_job_id:
            return {
                'type': 'ir.actions.act_window',
                'name': _('Configuration du Poste'),
                'res_model': 'hr.job',  # The model of the job
                'view_mode': 'form',
                'res_id': self.requested_job_id.id,  # Open the selected job's form view
                'target': 'current',
            }


    def action_see_applications(self):
        print("hello")


    # default methodes
    @api.model
    def create(self,vals):
        if vals.get('reference',_('Nouveau'))==_('Nouveau'):
            vals['reference'] = self.env['ir.sequence'].next_by_code('recruit_ink.demande_de_recrutement.sequence') or _("Nouveau")
        return super(RecruitInkDemande,self).create(vals)
    def write(self, vals):
        # Initialize an empty list to collect the messages
        messages = []


        # Check if job_description is being updated
        if 'job_description' in vals:
            for record in self:
                if record.job_description != vals['job_description']:
                    # Log a message to the chatter
                    messages.append(
                        f'<li>'
                        f'La description du poste a été modifiée'
                        f'</li>'
                    )
        if 'requirements' in vals:
            for record in self:
                if record.job_description != vals['requirements']:
                    # Log a message to the chatter
                    messages.append(
                        f'<li>'
                        f'Les requirements du poste on été modifiée'
                        f'</li>'
                    )
                    # If there are messages to log, post them in the chatter

        if messages:
            # Combine all messages into a list and format it as a single message
            message = Markup("".join(messages))

            for record in self:
                record.message_post(
                    body=message
                )


        # Call the super method to perform the actual write operation


        return super(RecruitInkDemande, self).write(vals)

and here is the Many2one field that I created in a inherited hr.employee class

from odoo import models, fields

class RecruitInkHrEmployee(models.Model):
    _inherit = 'hr.employee'

    demande_id= fields.Many2one("recruit_ink.demande","Recruit ink demande" )

the One 2 many field is employee_ids and the implementation is in onchange_requested_job_id

When I choose the job the tree view does get populated but when I save the records disappear.