Differences in Tags are not calculated correctly

[fbreckle]

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Hi,

terraform seems to recreate all Tags on an instance, even Tags that were unchanged.
This is a problem if recreation of a tag is not allowed by IAM permissions and in general unnecessary behavior. The aws API seems to silently succeed when creating duplicate tags.

Terraform Version

$ terraform -v
Terraform v0.11.10

• provider.aws v1.42.0

Affected Resource(s)

• aws_instance (but anything that is getting tagged probably)

Terraform Configuration Files

Start with

provider "aws" {
  region = "eu-west-1"
  version = "1.42"
}

resource "aws_instance" "web" {
  ami           = "ami-0a5e707736615003c"
  instance_type = "t2.micro"

  tags {
    Origin = "Terraform"
  }
}

then add another tag "Testtag" to the instance as per

tags {
    Origin = "Terraform"
    Testtag = "Testy"
  }

Debug Output

2018-11-05T18:21:17.617+0100 [DEBUG] plugin.terraform-provider-aws_v1.42.0_x4: 2018/11/05 18:21:17 [DEBUG] Creating tags: [{ 2018-11-05T18:21:17.617+0100 [DEBUG] plugin.terraform-provider-aws_v1.42.0_x4: Key: "Origin", 2018-11-05T18:21:17.617+0100 [DEBUG] plugin.terraform-provider-aws_v1.42.0_x4: Value: "Terraform" 2018-11-05T18:21:17.617+0100 [DEBUG] plugin.terraform-provider-aws_v1.42.0_x4: } { 2018-11-05T18:21:17.617+0100 [DEBUG] plugin.terraform-provider-aws_v1.42.0_x4: Key: "Testtag", 2018-11-05T18:21:17.617+0100 [DEBUG] plugin.terraform-provider-aws_v1.42.0_x4: Value: "Testy" 2018-11-05T18:21:17.617+0100 [DEBUG] plugin.terraform-provider-aws_v1.42.0_x4: }] for <instance_id>

Expected Behavior

Only the Tag "Testtag" should be created.

Actual Behavior

Terraform creates both Tags anew, aborting if (re-)creation of the old Tag is forbidden.

Steps to Reproduce

Modify the Tag list of an instance after creating it, then terraform apply

Important Factoids

I only tested and verified this with EC2 Instances, but the source code makes me believe that many more, if not all, taggable elements on aws have this issue. I cant think of an element where this behavior is desirable/required.

I also have the faulty method fixed already, I will make a pull request tomorrow. I just want to make sure this is indeed a bug and Im not overlooking something.

[bflad]

The fix for this has been merged and will release with version 1.43.1 of the AWS provider, likely later today. 👍

[bflad]

This has been released in version 1.43.1 of the AWS provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. Thanks!