[Bug]: Can't set warm_pool.min_size of aws_autoscaling_group to 0

[MetricMike]

Terraform and AWS Provider Version

Terraform v1.12.2
on linux_amd64
+ provider registry.terraform.io/hashicorp/aws v5.100.0

I believe the relevant line is still in main, so I suspect this bug is still present in v6.

Affected Resource(s) or Data Source(s)

• aws_autoscaling_group (warm_pool)

Expected Behavior

...
  warm_pool {
    pool_state                  = "Stopped"
    min_size                    = 0
    max_group_prepared_capacity = 0

    instance_reuse_policy {
      reuse_on_scale_in = false
    }
  }

This should set the warm pool's minimum size to 0

Actual Behavior

expandPutWarmPoolInput does not send the min_size attribute if it is set to 0, leaving the current min_size in place.

Relevant Error/Panic Output

No response

Sample Terraform Configuration

resource "aws_autoscaling_group" "example" {
  vpc_zone_identifier = ["subnet-example-1", "subnet-example-2"]
  desired_capacity    = 0
  min_size            = 0
  max_size            = 5

  launch_template {
    id      = "lt-example-1"
    version = "$Default"
  }

  warm_pool {
    pool_state                  = "Stopped"
    min_size                    = 0
    max_group_prepared_capacity = 0

    instance_reuse_policy {
      reuse_on_scale_in = false
    }
  }
}

Steps to Reproduce

1. terraform init
2. terraform apply

Debug Logging

No response

GenAI / LLM Assisted Development

No response

Important Facts and References

This is identical behavior to the max_group_prepared_capacity bug on #37173 that was fixed by #37174

I'm going to try to implement this fix since this looks so similar to that issue/pull, but if someone else gets there first that's fine :)

Would you like to implement a fix?

Yes

[github-actions]

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