if we are using a field with field_name different from the field in model that is used as source then this is failing and it should be

defaults[field.source] = default

I somehow missed your comment on this, but you're correct. The code above specifically checks for a compatible field source, but uses the serializerfield_name instead of thesource model field.

i had reported this and tried to work on it, but couldnt continue
and along with this issue other issue is there defined in the Issue below
#7005
#7003

Hi@anveshagarwal. I'm currently following up on that PR. That's what prompted my comment. 😄

For posterity's sake, my reasoning above was slightly wrong. Thesource checks are an indicator that we should be operating onfield.source instead offield.field_name, however the way to determine this is by looking atrun_validation. Before it callsrun_validators (then_read_only_defaults), it callsto_internal_value. At this point, the data has been converted to its source structure. So, it makes sense that the read-only defaults would also map to its source structure, instead of the raw field names.