Set default value (auto select a line in the child view) from a list for a Many2One value in Odoo 14 - odoo

Question

I have a parent model (Plant) which sends the active_id (plant_id) in the context as a default:
class Plant(models.Model):
_name = 'db.plant'
_description = 'db.plant'
name = fields.Char("Name", required=True)
...
Plant view with a many2one relation between them:
<odoo>
<data>
<record id="plant_list_view" model="ir.ui.view">
<field name="name">db.plant.view</field>
<field name="model">db.plant</field>
<field name="arch" type="xml">
<tree>
<field name="name"/>
...
</tree>
</field>
</record>
<record id="plant_form_view" model="ir.ui.view">
<field name="name">db.form.view</field>
<field name="model">db.plant</field>
<field name="arch" type="xml">
<form>
<sheet>
<group string="Plant">
<field name="name"/>
...
</group>
<group string="Components">
<notebook>
<page string="Data Sources">
<field name="data_source_ids" context="{'default_plant_id': active_id}">
<tree >
<field name="name"/>
...
<!-- <field name="plant_id"/> -->
</tree>
</field>
</page>
</notebook>
</group>
</sheet>
</form>
</field>
</record>
<record id="plant_action" model="ir.actions.act_window">
<field name="name">plant</field>
<field name="type">ir.actions.act_window</field>
<field name="res_model">db.plant</field>
<field name="view_mode">tree,form</field>
</record>
</data>
and his child model (Data_source):
class DataSource(models.Model):
_name = 'db.data_source'
_description = 'db.data_source'
name = fields.Char("Name", required=True)
plant_id = fields.Many2one('db.plant', name="Plant", required=True)
data_source view:
<odoo>
<data>
<record id="data_source_list_view" model="ir.ui.view">
<field name="name">db.data_source.view</field>
<field name="model">db.data_source</field>
<field name="arch" type="xml">
<tree>
<field name="name"/>
...
</tree>
</field>
</record>
<record id="data_source_form_view" model="ir.ui.view">
<field name="name">db.form.view</field>
<field name="model">db.data_source</field>
<field name="arch" type="xml">
<form>
<group>
<field name="name"/>
...
</group>
<group>
<field name="plant_id" domain="[('id', '=', context.default_plant_id)]" />
</group>
<group>
</group>
</form>
</field>
</record>
<record id="data_source_action" model="ir.actions.act_window">
<field name="name">Data Source</field>
<field name="type">ir.actions.act_window</field>
<field name="res_model">db.data_source</field>
<field name="view_mode">tree,form</field>
</record>
</data>
I know that the default_plant_id is received in the child because the plaint_id domain is filtering just my plant_id but I am not able to set it automatically as a default value. I need to click on the list and select my plant_id (which is the only element in the list).
I also tried adding an #api.on_change("plant_id") in the child (data_source) in two ways:
Option 1:
#api.onchange('plant_id')
def onchange_plant_id(self):
if self.plant_id:
context = dict(self._context or {})
return [(0,0,{'plant_id': context.get('default_plant_id')})]
giving me this exception:
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
File "/Users/albertocrespo/tools/odoo/odoo/http.py", line 640, in _handle_exception
return super(JsonRequest, self)._handle_exception(exception)
File "/Users/albertocrespo/tools/odoo/odoo/http.py", line 316, in _handle_exception
raise exception.with_traceback(None) from new_cause
AttributeError: 'list' object has no attribute 'get'
Option 2 (I am not sure what to send as a response, but the write statement is also not working):
#api.onchange('plant_id')
def onchange_your_many_to_one_field(self):
context = dict(self._context or {})
self.plant_id.write({'id':context.get('default_plant_id')})})
res = {}
return res
I need to auto-select my plant as an option in the data_source view before saving it.

Answer 1

There is no need of onchange method or anything on xml side - context level. You can simply use field plant_id in a relation one2many field data_source_ids.
Try with this:
data_source_ids = fields.One2many("db.data_source", "plant_id")