Error when using lifecycle rule with null values

[GusAntoniassi]

Description

When trying to use a lifecycle rule while passing null values for transition, noncurrent_version_transition and filter inputs, Terraform throws a "null value has no attributes" error. I believe this is due to how the for_each blocks are implemented:

        for_each = try(flatten([rule.value.expiration]), [])

Since there is no compact, the flatten call will return [null] which is a valid list with one value.

In my case the null values are coming from a variable with optional fields, so it would be best if the module could handle null values correctly.

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

Versions

• Module version [Required]: 4.5.0

• Terraform version: 1.7.5

• Provider version(s): 5.84.0

Reproduction Code [Required]

module "s3_bucket" {
  source = "terraform-aws-modules/s3-bucket/aws"

  bucket = "tftest-foobar-bucket"

  lifecycle_rule = [
    {
      id      = "foobar"
      enabled = true

      expiration = null

      transition = null

      noncurrent_version_expiration = null

      noncurrent_version_transition = null

      filter = {
        tags = null
      }
    }
  ]
}

Steps to reproduce the behavior:

• run terraform plan

Expected behavior

The plan to create a bucket with an empty lifecycle rule.

Actual behavior

Error:

│ Error: Attempt to get attribute from null value
│ 
│   on .terraform/modules/s3_bucket/main.tf line 281, in resource "aws_s3_bucket_lifecycle_configuration" "this":
│  281:           storage_class = transition.value.storage_class
│     ├────────────────
│     │ transition.value is null
│ 
│ This value is null, so it does not have any attributes.
╵
╷
│ Error: Attempt to get attribute from null value
│ 
│   on .terraform/modules/s3_bucket/main.tf line 302, in resource "aws_s3_bucket_lifecycle_configuration" "this":
│  302:           storage_class             = noncurrent_version_transition.value.storage_class
│     ├────────────────
│     │ noncurrent_version_transition.value is null
│ 
│ This value is null, so it does not have any attributes.
╵
╷
│ Error: Invalid function argument
│ 
│   on .terraform/modules/s3_bucket/main.tf line 317, in resource "aws_s3_bucket_lifecycle_configuration" "this":
│  317:         for_each = [for v in try(flatten([rule.value.filter]), []) : v if max(length(keys(v)), length(try(rule.value.filter.tags, rule.value.filter.tag, []))) == 1]
│ 
│ Invalid value for "inputMap" parameter: argument must not be null.
╵
╷
│ Error: Invalid function argument
│ 
│   on .terraform/modules/s3_bucket/main.tf line 337, in resource "aws_s3_bucket_lifecycle_configuration" "this":
│  337:         for_each = [for v in try(flatten([rule.value.filter]), []) : v if max(length(keys(v)), length(try(rule.value.filter.tags, rule.value.filter.tag, []))) > 1]
│ 
│ Invalid value for "inputMap" parameter: argument must not be null.