Redundant diff plan for fastly_service_vcl services that include logging_syslog.tls_ca_cert

[laynax]

Hi team

I have a fastly_service_vcl resource including a logging_syslog with tls_ca_cert enabled. Now by making any changes to service, even if it's not related to logging_syslog, I get to see logging_syslog block diff by executing terraform plan.

Digging deeper into the problem, showed it's caused by commiting tls_ca_cert string with a trailing \n (how I passed to it initially) into tfstate. So after each read, terraform compares cert with trailing \n in tfstate with the one without whitespace fetched from fastly-api.

I'm a new comer in GO world and wanted to contribute to your project, but couldn't find a proper way to solve the problem to submit a PR.

Terraform Version

Terraform v1.2.3
on linux_amd64

Affected Resource(s)

fastly_service_vcl

Terraform Configuration Files

resource "fastly_service_vcl" "test_service" {
  name = "test_service"
  comment = "comment"

  domain {
    name    = "domain.io"
    comment = "domain comment"
  }

  condition {
    name      = "Response from the Edge"
    priority  = 10
    statement = "fastly.ff.visits_this_service == 0"
    type      = "RESPONSE"
  }

  logging_syslog {
      name               = "rsyslog"
      response_condition = "Response from the Edge"
      address            = "rsyslog-nlb-7538ba8d23954192.elb.us-east-2.amazonaws.com"
      port               = 6514
      use_tls            = true
      tls_ca_cert        = <<-EOF
      -----BEGIN CERTIFICATE-----
      XXXX
      -----END CERTIFICATE-----
      EOF

      tls_hostname       = "tlshostname.host"
      format             = "%h %l %u %t \"%r\" %\u003es %b"
      format_version     = 2
      message_type       = "loggly"
      placement = "none"
  }
}

Expected Behavior

Changing service comment must be the only modified line in terraform plan

Actual Behavior

Redundant diff on logging_syslog block.

Steps to Reproduce

1. terraform apply
2. make change to any field (image above is a result of changing test_service.comment)
3. terraform plan

[Integralist]

Thanks for opening this issue. I believe the following comment might be what you need...

https://github.com/fastly/terraform-provider-fastly/issues/231#issuecomment-632840094

[laynax]

@Integralist Thanks for your respond. Yes, using trimspace() would do the trick too. However, I was trying to fix this on provider side.

More details on my digging: I tried using DiffSuppressFunc and StateFunc but them both didn't work (in case of doing such, we receive a newVal here with 2 elements which the second one is not filled with data and causes erorr). I think the reason for that is SetType is not supported by terraform any more.