aws_lambda_alias is recreated when function_name changes from function name to ARN and viceversa

[angelyan]

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Terraform Version

Terraform v0.12.20
+ provider.aws v2.58.0

Affected Resource(s)

• aws_lambda_alias

Terraform Configuration Files

resource "aws_lambda_alias" "alias" {
- function_name = "lambda"
+ function_name = "arn:aws:lambda:<region>:<account>:function:lambda"
  function_version = "..."
  name = "alias"
}

Expected Behavior

terraform plan should show no changes.

Actual Behavior

terraform plan shows that alias will be recreated even though the ARN points to the same function.

Terraform will perform the following actions:

  # aws_lambda_alias.alias must be replaced
-/+ resource "aws_lambda_alias" "alias" {
      ~ arn              = "arn:aws:lambda:<region>:<account>:function:lambda:alias" -> (known after apply)
        description      = "..."
      ~ function_name    = "lambda" -> "arn:aws:lambda:<region>:<account>:function:lambda" # forces replacement
        function_version = "..."
      ~ id               = "arn:aws:lambda:<region>:<account>:function:lambda:alias" -> (known after apply)
      ~ invoke_arn       = "..." -> (known after apply)
        name             = "alias"
    }

Plan: 1 to add, 0 to change, 1 to destroy.

Steps to Reproduce

1. Create a lambda alias with function_name argument set to the name of the function.
2. Change function_name to the ARN of the function.
3. Run terraform plan.

[bflad]

This difference suppression has been merged and will release with version 2.59.0 of the Terraform AWS Provider, later this week. Thanks to @angelyan for the implementation. 👍

[ghost]

This has been released in version 2.59.0 of the Terraform AWS provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template for triage. Thanks!

[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!