Update for VPCs also

Author: YakDriver

website/docs/r/ec2_transit_gateway_route_table_association.html.markdown

@@ -55,6 +55,43 @@ resource "aws_ec2_transit_gateway_route_table_association" "example" {
 
 ~> **NOTE:** Avoid using the `aws_ec2_transit_gateway_dx_gateway_attachment` data source to retrieve the attachment ID, as this can cause unnecessary resource recreation when unrelated attributes of the Direct Connect Gateway association change (such as `allowed_prefixes`). Always reference the `transit_gateway_attachment_id` attribute directly from the `aws_dx_gateway_association` resource when available.
 
+### VPC Attachment Association
+
+For VPC attachments, always reference the attachment resource's `id` attribute directly. Avoid using data sources or lifecycle rules that might cause the attachment ID to become unknown during planning:
+
+```terraform
+resource "aws_vpc" "example" {
+  cidr_block = "10.0.0.0/16"
+}
+
+resource "aws_subnet" "example" {
+  vpc_id     = aws_vpc.example.id
+  cidr_block = "10.0.1.0/24"
+}
+
+resource "aws_ec2_transit_gateway" "example" {
+  description = "example"
+}
+
+resource "aws_ec2_transit_gateway_vpc_attachment" "example" {
+  subnet_ids         = [aws_subnet.example.id]
+  transit_gateway_id = aws_ec2_transit_gateway.example.id
+  vpc_id             = aws_vpc.example.id
+}
+
+resource "aws_ec2_transit_gateway_route_table" "example" {
+  transit_gateway_id = aws_ec2_transit_gateway.example.id
+}
+
+# Correct: Reference the VPC attachment ID directly
+resource "aws_ec2_transit_gateway_route_table_association" "example" {
+  transit_gateway_attachment_id  = aws_ec2_transit_gateway_vpc_attachment.example.id
+  transit_gateway_route_table_id = aws_ec2_transit_gateway_route_table.example.id
+}
+```
+
+~> **NOTE:** When the `transit_gateway_attachment_id` changes (for example, when a VPC attachment is replaced), this resource will be recreated. This is the correct behavior to maintain consistency between the attachment and its route table association.
+
 ## Argument Reference
 
 This resource supports the following arguments:

website/docs/r/ec2_transit_gateway_route_table_propagation.html.markdown

@@ -55,6 +55,43 @@ resource "aws_ec2_transit_gateway_route_table_propagation" "example" {
 
 ~> **NOTE:** Avoid using the `aws_ec2_transit_gateway_dx_gateway_attachment` data source to retrieve the attachment ID, as this can cause unnecessary resource recreation when unrelated attributes of the Direct Connect Gateway association change (such as `allowed_prefixes`). Always reference the `transit_gateway_attachment_id` attribute directly from the `aws_dx_gateway_association` resource when available.
 
+### VPC Attachment Propagation
+
+For VPC attachments, always reference the attachment resource's `id` attribute directly. Avoid using data sources or lifecycle rules that might cause the attachment ID to become unknown during planning:
+
+```terraform
+resource "aws_vpc" "example" {
+  cidr_block = "10.0.0.0/16"
+}
+
+resource "aws_subnet" "example" {
+  vpc_id     = aws_vpc.example.id
+  cidr_block = "10.0.1.0/24"
+}
+
+resource "aws_ec2_transit_gateway" "example" {
+  description = "example"
+}
+
+resource "aws_ec2_transit_gateway_vpc_attachment" "example" {
+  subnet_ids         = [aws_subnet.example.id]
+  transit_gateway_id = aws_ec2_transit_gateway.example.id
+  vpc_id             = aws_vpc.example.id
+}
+
+resource "aws_ec2_transit_gateway_route_table" "example" {
+  transit_gateway_id = aws_ec2_transit_gateway.example.id
+}
+
+# Correct: Reference the VPC attachment ID directly
+resource "aws_ec2_transit_gateway_route_table_propagation" "example" {
+  transit_gateway_attachment_id  = aws_ec2_transit_gateway_vpc_attachment.example.id
+  transit_gateway_route_table_id = aws_ec2_transit_gateway_route_table.example.id
+}
+```
+
+~> **NOTE:** When the `transit_gateway_attachment_id` changes (for example, when a VPC attachment is replaced), this resource will be recreated. This is the correct behavior to maintain consistency between the attachment and its route table propagation.
+
 ## Argument Reference
 
 This resource supports the following arguments: