Odoo - Hide button for specific user

I have understood that you have a fixed list of users who will be able to approve and other fixed list of users who will be able to reject. In spite of being a few users, I would create two groups and use groups attribute on your buttons, but if even so you do not want to create a couple of groups for them, you can do this:

from openerp import models, api
import json
from lxml import etree

FIRST_APPROVE = []  # Fill this list with the IDs of the users who can update approve
SECOND_APPROVE = []  # Fill this list with the IDs of the users who can update reject

class YourClass(models.Model):
    _inherit = 'your.class'

    def update_json_data(self, json_data=False, update_data={}):
        ''' It updates JSON data. It gets JSON data, converts it to a Python
        dictionary, updates this, and converts the dictionary to JSON data
        again. '''
        dict_data = json.loads(json_data) if json_data else {}
        dict_data.update(update_data)
        return json.dumps(dict_data, ensure_ascii=False)

    def set_modifiers(self, element=False, modifiers_upd={}):
        ''' It updates the JSON modifiers with the specified data to indicate
        if a XML tag is readonly or invisible or not. '''
        if element is not False:  # Do not write only if element:
            modifiers = element.get('modifiers') or {}
            modifiers_json = self.update_json_data(
                modifiers, modifiers_upd)
            element.set('modifiers', modifiers_json)

    @api.model
    def fields_view_get(self, view_id=None, view_type='form', toolbar=False,
                        submenu=False):
        res = super(YourClass, self).fields_view_get(
            view_id=view_id, view_type=view_type, toolbar=toolbar,
            submenu=submenu)

        doc = etree.XML(res['arch'])

        if view_type == 'form':
            if self.env.uid in FIRST_APPROVE:
                upd_approve_btn_search = doc.xpath("//button[@name='update_approve']")
                upd_approve_btn = upd_approve_btn_search[0] \
                    if upd_approve_btn_search else False
                if upd_approve_btn:
                    self.set_modifiers(upd_approve_btn, {'invisible': False, })

            if self.env.uid in SECOND_APPROVE:
                upd_reject_btn_search = doc.xpath("//button[@name='update_reject']")
                upd_reject_btn = upd_reject_btn_search[0] \
                    if upd_reject_btn_search else False
                if upd_reject_btn:
                    self.set_modifiers(upd_reject_btn, {'invisible': False, })

        res['arch'] = etree.tostring(doc)
        return res

FIRST APPROVE and SECOND_APPROVE will be const in which you must introduce the fixed IDS of the users who can perform the respective action (for example: FIRST APPROVE = [2, 7, 9]).

YourClass must be the class in which you have declared the methods of your buttons (the one in which you have declared update_approve and update_reject).

IMPORTANT: with this code, your buttons must be always invisible (write invisible="1" at your XML view), because after loading the XML code, the fields_view_get will overwrite the invisible value to set 0.

This is an uncommon way to manage your purpose, but unfortunately I think it is the simplest one if you do not want to create groups. I hope it helps you and other users!

One of the thing i know to use a field in attrs the field must be Mentionsed in the form. i don't know how to get the value of the user id in the form. but if there is not a short way like uid or user you can work arround this, just create a m2o field to res.users make this field compute field with store = False.

    # by default store = False this means the value of this field
    # is always computed.
    current_user = fields.Many2one('res.users', compute='_get_current_user')

    @api.depends()
    def _get_current_user(self):
        for rec in self:
            rec.current_user = self.env.user

and you can use this field in your form.

    <xpath expr="//sheet" position="before">
              <header>
                 <!-- fin a good place for the field if i make the header look ugly -->
                <!-- make invisible -->
                 <field name="current_user" invisible="1"/>
                                                                                    <!-- hope it work like this -->
                <button name="update_approve" attrs="{'invisible':[('first_approve', '=', current_user)]}" string="Approve" type="object" class="oe_highlight"/>
                <button name="update_reject" attrs="{'invisible':[('second_approve', '=', current_user)]}" string="Reject" type="object" class="btn-danger"/>
              </header>
     </xpath>

sorry for my english.