I have an onchange method describe in the model and based on that values i want to store values in the read-only fields, its happen buts while saving its gone.
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@api.onchange('product_id')

def onchange_product_id(self):

cr = self.env.cr

desc = ''

uom = -1

for rec in self:

cr.execute('''SELECT

product_uom.id AS uom,

product_template.name AS desc,

product_hsn_tax_code.hsn_name AS hsn_code,

product_hsn_tax_code.tax_percentage AS gst_value

FROM

product_uom JOIN

product_template ON

product_uom.id=product_template.uom_id JOIN

product_product ON

product_template.id=product_product.product_tmpl_id JOIN

product_hsn_tax_code ON

product_hsn_tax_code.id=product_template.hsn_id

WHERE

product_product.id = cast(%s AS INTEGER)''', ((rec.product_id.id),))

for line in cr.dictfetchall():

uom = line['uom']

desc = line['desc']

return {'value' :{

'uom_id':uom,

'description':desc,

}}

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