ignore_changes compatibility with TF version 1.2

[pat-s]

Description

TF 1.2 has implemented a change WRT to the handling of ignore_changes, see here.

• ✋ I have searched the open/closed issues and my issue is not listed.

Versions

• Module version [Required]:

4.3.0

• Terraform version:

Terraform v1.2.0
on darwin_arm64
+ provider registry.terraform.io/hashicorp/aws v4.12.1
+ provider registry.terraform.io/hashicorp/cloudinit v2.2.0
+ provider registry.terraform.io/hashicorp/googleworkspace v0.6.0
+ provider registry.terraform.io/hashicorp/helm v2.5.1
+ provider registry.terraform.io/hashicorp/kubernetes v2.11.0
+ provider registry.terraform.io/hashicorp/local v2.2.2
+ provider registry.terraform.io/hashicorp/random v3.1.3
+ provider registry.terraform.io/hashicorp/vault v3.5.0
+ provider registry.terraform.io/terraform-aws-modules/http v2.4.1

• Provider version(s):

Reproduction Code [Required]

Steps to reproduce the behavior:

1. Execute any TF code which uses the model terraform-aws-modules/rds/aws with TF 1.2

Expected behavior

No warning is being issued.

Actual behavior

╷
│ Warning: Redundant ignore_changes element
│ 
│   on .terraform/modules/postgres.postgres/modules/db_instance/main.tf line 26, in resource "aws_db_instance" "this":
│   26: resource "aws_db_instance" "this" {
│ 
│ Adding an attribute name to ignore_changes tells Terraform to ignore future changes to the argument in configuration after the object has been
│ created, retaining the value originally configured.
│ 
│ The attribute latest_restorable_time is decided by the provider alone and therefore there can be no configured value to compare with. Including
│ this attribute in ignore_changes has no effect. Remove the attribute from ignore_changes to quiet this warning.

Terminal Output Screenshot(s)

Additional context

AFAICS the following part could/should be removed in main.tf:
https://github.com/terraform-aws-modules/terraform-aws-rds/blob/master/modules/db_instance/main.tf#L120-L124

cc @wael-sadek @mbannert

[antonbabenko]

I believe that this behavior should have been a feature flag in Terraform 1.2 which can be optionally disabled by some users who don't want to see warnings like this.

Currently, we don't have to increase the minimum version of Terraform required for this module because we don't use features introduced in the recent versions.

I don't think we will have a way to fix such warnings in the modules also because we can't use variables inside of ignore_changes block and users of Terraform <1.2 don't have such an issue.

[pat-s]

Sure, fully understand! Just wanted to write down this "issue" so that others can possibly find it (and also your reply to it) 🙂

[michelzanini]

If you were to remove the ignore_changes previous versions of Terraform would not break but start displaying a block of "Changes made outside Terraform". That is not nice, but it's less critical than a warning that happens on 1.2.

That way I think the best compromise is to leave the "Changes made outside Terraform" for previous versions and no warnings on most recent versions, since the future is 1.2+ anyway.

[michelzanini]

Can we do the same as the EKS module?
terraform-aws-modules/terraform-aws-eks#2114

[antonbabenko]

This issue has been resolved in version 5.0.0 🎉

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