What is the default behavior for associate_public_ip_address

Terraform Providers AWS
1

I am looking at this documentation and cannot determine the default value for the field associate_public_ip_address

thx
Alan

2

Logically, it should be false. But I can’t find the actual reference in the SDK.

3

Seems to default to true.

4

I’m necroing a 5 year old thread because somehow it’s still the top result for this subject and its answer is incomplete.
The Short Answer:

associate_public_ip_address does not have a stateless default. It defaults to the behavior of the subnet it’s in, with relation to the map_public_ip_on_launch attribute.

My Reasoning:
associate_public_ip_address for aws_instance left as null doesn’t actually default to anything beyond “what the subnet says it should do.”

If you are making this aws_instance inside of a subnet with map_public_ip_on_launch set to true, the aws_instance will get a public ipv4 address regardless of your specifying true, false, or null on associate_public_ip_address.

The matrix is as such:
map_public_ip_on_launch aws_subnet, false aws_instance >>> true
map_public_ip_on_launch aws_subnet, true aws_instance >>> true
map_public_ip_on_launch aws_subnet, null aws_instance >>> true
no map_public_ip_on_launch aws_subnet, false aws_instance >>> false
no map_public_ip_on_launch aws_subnet, true aws_instance >>> true
no map_public_ip_on_launch aws_subnet, null aws_instance >>> false

So, rather than this being a default of true the actual default is “whatever the subnet tells the instance to do.”
As an aside, still receiving a public IP regardless of setting it false in a map_public_ip_on_launch subnet makes the false setting useless. I question the need for anything other than true and null to exist for this parameter, given the effective uselessness of this attribute in overriding the subnet’s parameters.