Altering imported Lambda function resource results in a diffs didn't match during apply error

[bleggett]

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Terraform Version

0.11.8

Affected Resource(s)

• aws_lambda_function

Terraform Configuration Files

# Deploy the function with the correct role.
resource "aws_lambda_function" "proxyfunc" {
  function_name    = "${var.env_prefix}-proxyfunc"
  role             = "${aws_iam_role.lambda-role.arn}"
  handler          = "proxyfunc.handler"
  runtime          = "nodejs8.10"

  lifecycle {
    ignore_changes = [
      "function_name",
      "runtime",
      "handler"
    ]
  }
}

Have to use ignore_changes here, because I only want to update the function role for the existing function, and those 3 fields are required if I do not ignore them.

Debug Output

https://gist.github.com/bleggett/48dbc654c9e0f295e2a1a6ac997a1276

diffs didn't match during apply. This is a bug with Terraform and should be reported as a GitHub Issue.

Expected Behavior

Given a preexisting Lambda function named test-func

running

terraform import --function-name test-func
terraform apply -var env_prefix=fubar

should result in the function being imported, and the existing resource should be updated with the new role.

Actual Behavior

terraform input succeeds, terraform apply fails with the above diff exception.

Steps to Reproduce

terraform import --function-name test-func
terraform apply -var env_prefix=fubar

[bleggett]

More info by following the below steps:

1. Running terraform input on the Lambda function works.

2. Running terraform apply does NOT show the correct set of changes for the lambda function (the lambda role is NOT updated), and fails with the same diff out of sync exception as before.

3. And running terraform apply a second time immediately after the above step succeeds without a diff exception and outputs and performs the correct operation.

So weirdly if I just rerun apply it works the second time around.

[bleggett]

After some more investigation I am inclined to think this is an issue with core Terraform, and not this provider, though I lack the insight into the codebase to be sure of that.

[aeschright]

Hi @bleggett ! Unfortunately the message you saw isn't enough for us to go on to investigate the error. The debugging situation should be improved if you upgrade to Terraform 0.12 and the latest AWS provider. If you still see an error in this situation, please open a new bug report and we'll dig into it. 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!