Terraform erroneously plans to remove routes with origin EnableVgwRoutePropagation.

[ojongerius]

Context: enabling route propagation from Virtual Gateways is a feature not yet supported by Terraform, that we currently enable, together with some other features, via other scripts.

Ignoring routes with an origin of EnableVgwRoutePropagation in resourceAwsRouteTableRead restores normality.

Test config:

resource "aws_route_table" "foo" {
    vpc_id = "${var.vpc.id}"
    route = {
        cidr_block = "0.0.0.0/0"
        instance_id = "${aws_instance.bar.id}"
    }
}

Running in planning mode without patching resourceAwsRouteTableRead for a route table
consisting of a default route set by Terraform and 3 routes propagated via Virtual Private Gateway vgw-baz.

~ aws_route_table.foo
    route.#:             "4" => "1"
    route.0.cidr_block:  "0.0.0.0/0" => "0.0.0.0/0"
    route.0.gateway_id:  "" => ""
    route.0.instance_id: "i-bar" => "i-bar"
    route.1.cidr_block:  "172.16.0.0/12" => ""
    route.1.gateway_id:  "vgw-baz" => ""
    route.1.instance_id: "" => ""
    route.2.cidr_block:  "192.168.0.0/16" => ""
    route.2.gateway_id:  "vgw-baz" => ""
    route.2.instance_id: "" => ""
    route.3.cidr_block:  "10.0.0.0/8" => ""
    route.3.gateway_id:  "vgw-baz" => ""
    route.3.instance_id: "" => ""

Terraform correctly reports there are no changes after applying the following patch (git diff v0.3.5..ignore_propagated_routes):

diff --git a/builtin/providers/aws/resource_aws_route_table.go b/builtin/providers/aws/resource_aws_route_table.go
index 841e456..71c1cc0 100644
--- a/builtin/providers/aws/resource_aws_route_table.go
+++ b/builtin/providers/aws/resource_aws_route_table.go
@@ -114,6 +114,10 @@ func resourceAwsRouteTableRead(d *schema.ResourceData, meta interface{}) error {
                        continue
                }

+               if r.Origin == "EnableVgwRoutePropagation" {
+                       continue
+               }
+
                m := make(map[string]interface{})
                m["cidr_block"] = r.DestinationCidrBlock

[ghost]

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