[Bug]: route tables shows a diff for empty entries

[heshammekky-sc]

Terraform Core Version

1.4.6

AWS Provider Version

4.37.0

Affected Resource(s)

aws_route_table

Expected Behavior

Right now, we have a route table entry (a route in aws_route_table) that looks like this

  route {
    ipv6_cidr_block           = "::/0"
    gateway_id                = <gateway-id>
    egress_only_gateway_id    = ""
    nat_gateway_id            = ""
    network_interface_id      = ""
    transit_gateway_id        = ""
    vpc_peering_connection_id = ""
  }

The route table contains other entries that are similar. When we add a new route entry, ideally we should see one new entry added to the route table. However, we see all entries are removed and re-added because we are missing some of the fields with empty string (e.g. instance_id, cidr_block or some other field).

When we try to add all these entries to get a clean diff output, it reject cidr_block = "" because it validates it against being a valid CIDR block.

An ideal configuration would be something like this where we only define the entries we can about in a route, and the rest is actually optional.

  route {
    ipv6_cidr_block           = "::/0"
    gateway_id                = <gateway-id>
  }

Actual Behavior

The actual behavior we observe is that all route table entries are deleted and re-added. In addition, we cannot pass cidr_block = "" to get a clean diff output, and we must define all empty entries to get the desired output which is not possible in this case.

Relevant Error/Panic Output Snippet

No response

Terraform Configuration Files

N/A

Steps to Reproduce

• create a route table with one route entry
• add a new route table entry
• you will see entries deleted and re-added

Debug Output

No response

Panic Output

No response

Important Factoids

No response

References

No response

Would you like to implement a fix?

None

[github-actions[bot]]

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[ewbankkit]

@heshammekkysc Thanks for raising this issue. It has already been noticed in #17198. I'm going to close this one as a duplicate so that we can concentrate discussion in the linked issue. Please add any additional comments there.

[ewbankkit]

Following the merge of https://github.com/hashicorp/terraform-provider-aws/pull/30804 we should be able to address this for the upcoming v5.0.0 release of the Terraform AWS Provider.

[heshammekky-sc]

Thank you. Would that address the need of having to specify all the empty entries in the route? This didn't come across from the discussion in the other issue.

[github-actions[bot]]

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 have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.