terraform-provider-aws: data source aws_ec2_transit_gateway_route_table doesn't feed data properly in plan phase to resource "aws_ec2_transit_gateway_route"

Community Note

• Please vote on this issue by adding a 👍 reaction to the original issue to help the community and maintainers prioritize this request
• Please do not leave “+1” or other comments that do not add relevant new information or questions, they generate extra noise for issue followers and do not help prioritize the request
• If you are interested in working on this issue or have submitted a pull request, please leave a comment

Terraform Version

Terraform v0.12.19

• provider.aws v2.44.0
• provider.random v2.2.1

Affected Resource(s)

• aws_ec2_transit_gateway_route
• data source: aws_ec2_transit_gateway_route_table

Terraform Configuration Files

provider "random" {
}

resource "random_id" "id" {
  byte_length = 4
}

locals {
  id = random_id.id.hex
}

locals {
  name = "tgw-test"
}

resource "aws_ec2_transit_gateway" "tgw-private" {
  tags = {
    Name = "${local.name}-private-${local.id}"
  }
}

resource "aws_ec2_transit_gateway" "tgw-public" {
  tags = {
    Name = "${local.name}-public-${local.id}"
  }
}

###############################################
# Maintain private Route Table of TGWA Routes #
###############################################
data "aws_ec2_transit_gateway_route_table" "tgwrtb" {
  filter {
    name   = "transit-gateway-id"
    values = [aws_ec2_transit_gateway.tgw-private.id]
  }
}

resource "aws_ec2_transit_gateway_route" "add_private_route_1" {
  destination_cidr_block         = "192.168.1.0/27"
  transit_gateway_attachment_id  = "tgw-1111111111"
  transit_gateway_route_table_id = data.aws_ec2_transit_gateway_route_table.tgwrtb.id
}

Debug Output

Panic Output

Expected Behavior

Terraform should start creating the resources and querying the data source once needed before creating the resource.

Actual Behavior

terraform analyzes the code and cannot resolve the data source properly so it fails.

$ terraform plan
Refreshing Terraform state in-memory prior to plan...
The refreshed state will be used to calculate this plan, but will not be
persisted to local or remote state storage.


------------------------------------------------------------------------

Error: "transit_gateway_route_table_id": required field is not set

  on main.tf line 38, in resource "aws_ec2_transit_gateway_route" "add_private_route_1":
  38: resource "aws_ec2_transit_gateway_route" "add_private_route_1" {

Steps to Reproduce

1. terraform plan

Important Factoids

References

• #0000