[Bug]: aws_lambda_function with empty environment variables map flaps

[oeuftete]

Terraform Core Version

1.3.7

AWS Provider Version

4.53.0

Affected Resource(s)

• aws_lambda_function

Expected Behavior

When setting the following block in aws_lambda_function, the resource should not repeatedly want to apply a change:

  environment {
    variables = {}
  }

Actual Behavior

Planning after an apply showed the environment block being added again.

Relevant Error/Panic Output Snippet

$ terraform apply "tfplan"
aws_iam_role.function: Creating...
aws_iam_role.function: Creation complete after 1s [id=environment-bug-repro-test]
aws_lambda_function.function: Creating...
aws_lambda_function.function: Still creating... [10s elapsed]
aws_lambda_function.function: Still creating... [20s elapsed]
aws_lambda_function.function: Creation complete after 22s [id=environment-bug-repro-test]

$ terraform plan
aws_iam_role.function: Refreshing state... [id=environment-bug-repro-test]
aws_lambda_function.function: Refreshing state... [id=environment-bug-repro-test]

Terraform used the selected providers to generate the following execution plan. Resource actions are indicated with the following symbols:
  ~ update in-place

Terraform will perform the following actions:

  # aws_lambda_function.function will be updated in-place
  ~ resource "aws_lambda_function" "function" {
        id                             = "environment-bug-repro-test"
        tags                           = {}
        # (21 unchanged attributes hidden)

      + environment {}

        # (2 unchanged blocks hidden)
    }

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

Terraform Configuration Files

locals {
  test_name = "environment-bug-repro-test"
}

resource "aws_lambda_function" "function" {
  filename         = "lambda.zip"
  function_name    = local.test_name
  role             = aws_iam_role.function.arn
  handler          = "lambda_function.lambda_handler"
  runtime          = "ruby2.7"
  source_code_hash = filebase64sha256("lambda.zip")

  environment {
    variables = {}
  }
}

resource "aws_iam_role" "function" {
  name = local.test_name

  assume_role_policy = <<EOF
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Action": "sts:AssumeRole",
      "Principal": {
        "Service": "lambda.amazonaws.com"
      },
      "Effect": "Allow",
      "Sid": ""
    }
  ]
}
EOF
}

Steps to Reproduce

terraform plan -out tfplan
terraform apply tfplan
terraform plan

Debug Output

No response

Panic Output

No response

Important Factoids

Workarounds

If you're just specifying it statically, don't add the environment block. If it's a scenario where you are passing the environment variables as a (possibly empty) map, this worked for me:

  dynamic "environment" {
    for_each = length(var.env_vars) == 0 ? [] : ["dummy"]

    content {
      variables = var.env_vars
    }
  }

References

Looks similar to #28495.

Would you like to implement a fix?

None

[github-actions]

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[github-actions]

This functionality has been released in v4.59.0 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. Thank you!

[github-actions]

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