[Bug] consul_intention makes Terraform panics if the resource has been deleted

[remilapeyre]

When a consul_intention resource is deleted manually, subsequent plans panic when reading this resource.

This is very similar to #69

As far as I can tell after a quick glance at other resources, they seem not to have this bug although a more in-depth check should be done.

Steps to Reproduce

➜  terraform-provider-consul git:(catalog-fix) cat example.tf
resource "consul_intention" "database" {
  source_name      = "api"
  destination_name = "db"
  action           = "allow"
}
➜  terraform-provider-consul git:(catalog-fix) terraform apply

An execution plan has been generated and is shown below.
Resource actions are indicated with the following symbols:
  + create

Terraform will perform the following actions:

  + consul_intention.database
      id:               <computed>
      action:           "allow"
      destination_name: "db"
      source_name:      "api"


Plan: 1 to add, 0 to change, 0 to destroy.

Do you want to perform these actions?
  Terraform will perform the actions described above.
  Only 'yes' will be accepted to approve.

  Enter a value: yes

consul_intention.database: Creating...
  action:           "" => "allow"
  destination_name: "" => "db"
  source_name:      "" => "api"
consul_intention.database: Creation complete after 0s (ID: 2056a436-8578-9dc4-3a9d-eaa257bfd628)

Apply complete! Resources: 1 added, 0 changed, 0 destroyed.
➜  terraform-provider-consul git:(catalog-fix) consul intention delete api db
Intention deleted.
➜  terraform-provider-consul git:(catalog-fix) terraform apply
consul_intention.database: Refreshing state... (ID: 2056a436-8578-9dc4-3a9d-eaa257bfd628)

Error: Error refreshing state: 1 error(s) occurred:

* consul_intention.database: 1 error(s) occurred:

* consul_intention.database: consul_intention.database: unexpected EOF


panic: runtime error: invalid memory address or nil pointer dereference
2018-12-27T16:02:34.913+0100 [DEBUG] plugin.terraform-provider-consul: [signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x1822e02]
2018-12-27T16:02:34.914+0100 [DEBUG] plugin.terraform-provider-consul:
2018-12-27T16:02:34.914+0100 [DEBUG] plugin.terraform-provider-consul: goroutine 8 [running]:
2018-12-27T16:02:34.914+0100 [DEBUG] plugin.terraform-provider-consul: github.com/terraform-providers/terraform-provider-consul/consul.resourceConsulIntentionRead(0xc000201960, 0x1a04cc0, 0xc0001ec3c0, 0xc000201960, 0x0)
2018-12-27T16:02:34.914+0100 [DEBUG] plugin.terraform-provider-consul:  /Users/remi/go/src/github.com/terraform-providers/terraform-provider-consul/consul/resource_consul_intention.go:175 +0x242
2018-12-27T16:02:34.914+0100 [DEBUG] plugin.terraform-provider-consul: github.com/terraform-providers/terraform-provider-consul/vendor/github.com/hashicorp/terraform/helper/schema.(*Resource).Refresh(0xc0002677a0, 0xc0003bef50, 0x1a04cc0, 0xc0001ec3c0, 0xc0003ab510, 0x10bf501, 0x189b1e0)
2018-12-27T16:02:34.914+0100 [DEBUG] plugin.terraform-provider-consul:  /Users/remi/go/src/github.com/terraform-providers/terraform-provider-consul/vendor/github.com/hashicorp/terraform/helper/schema/resource.go:352 +0x160
2018-12-27T16:02:34.914+0100 [DEBUG] plugin.terraform-provider-consul: github.com/terraform-providers/terraform-provider-consul/vendor/github.com/hashicorp/terraform/helper/schema.(*Provider).Refresh(0xc000267810, 0xc0003bef00, 0xc0003bef50, 0xc0003cc400, 0x18, 0x2539000)
2018-12-27T16:02:34.914+0100 [DEBUG] plugin.terraform-provider-consul:  /Users/remi/go/src/github.com/terraform-providers/terraform-provider-consul/vendor/github.com/hashicorp/terraform/helper/schema/provider.go:308 +0x92
2018-12-27T16:02:34.914+0100 [DEBUG] plugin.terraform-provider-consul: github.com/terraform-providers/terraform-provider-consul/vendor/github.com/hashicorp/terraform/plugin.(*ResourceProviderServer).Refresh(0xc0001a4140, 0xc00052ecb0, 0xc00052ef00, 0x0, 0x0)
2018-12-27T16:02:34.914+0100 [DEBUG] plugin.terraform-provider-consul:  /Users/remi/go/src/github.com/terraform-providers/terraform-provider-consul/vendor/github.com/hashicorp/terraform/plugin/resource_provider.go:549 +0x4e
2018-12-27T16:02:34.914+0100 [DEBUG] plugin.terraform-provider-consul: reflect.Value.call(0xc0000a35c0, 0xc0003c00e0, 0x13, 0x1a312c0, 0x4, 0xc000079f18, 0x3, 0x3, 0xc0000c1700, 0x0, ...)
2018-12-27T16:02:34.914+0100 [DEBUG] plugin.terraform-provider-consul:  /usr/local/Cellar/go/1.11.4/libexec/src/reflect/value.go:447 +0x454
2018-12-27T16:02:34.914+0100 [DEBUG] plugin.terraform-provider-consul: reflect.Value.Call(0xc0000a35c0, 0xc0003c00e0, 0x13, 0xc0002df718, 0x3, 0x3, 0x0, 0x0, 0x0)
2018-12-27T16:02:34.914+0100 [DEBUG] plugin.terraform-provider-consul:  /usr/local/Cellar/go/1.11.4/libexec/src/reflect/value.go:308 +0xa4
2018-12-27T16:02:34.914+0100 [DEBUG] plugin.terraform-provider-consul: net/rpc.(*service).call(0xc0003e6a40, 0xc0000d6730, 0xc0000be700, 0xc0000be870, 0xc000198f00, 0xc000161e00, 0x189b1a0, 0xc00052ecb0, 0x16, 0x189b1e0, ...)
2018-12-27T16:02:34.914+0100 [DEBUG] plugin.terraform-provider-consul:  /usr/local/Cellar/go/1.11.4/libexec/src/net/rpc/server.go:384 +0x14e
2018-12-27T16:02:34.914+0100 [DEBUG] plugin.terraform-provider-consul: created by net/rpc.(*Server).ServeCodec
2018-12-27T16:02:34.914+0100 [DEBUG] plugin.terraform-provider-consul:  /usr/local/Cellar/go/1.11.4/libexec/src/net/rpc/server.go:481 +0x47e
2018-12-27T16:02:34.916+0100 [DEBUG] plugin: plugin process exited: path=/Users/remi/.terraform.d/plugins/terraform-provider-consul
2018/12/27 16:02:34 [ERROR] root: eval: *terraform.EvalRefresh, err: consul_intention.database: unexpected EOF
2018/12/27 16:02:34 [ERROR] root: eval: *terraform.EvalSequence, err: consul_intention.database: unexpected EOF
2018/12/27 16:02:34 [TRACE] [walkRefresh] Exiting eval tree: consul_intention.database
2018/12/27 16:02:34 [TRACE] dag/walk: upstream errored, not walking "provider.consul (close)"
2018/12/27 16:02:34 [DEBUG] plugin: waiting for all plugin processes to complete...
2018-12-27T16:02:34.916+0100 [WARN ] plugin: error closing client during Kill: err="connection is shut down"



!!!!!!!!!!!!!!!!!!!!!!!!!!! TERRAFORM CRASH !!!!!!!!!!!!!!!!!!!!!!!!!!!!

Terraform crashed! This is always indicative of a bug within Terraform.
A crash log has been placed at "crash.log" relative to your current
working directory. It would be immensely helpful if you could please
report the crash with Terraform[1] so that we can fix this.

When reporting bugs, please include your terraform version. That
information is available on the first line of crash.log. You can also
get it by running 'terraform --version' on the command line.

[1]: https://github.com/hashicorp/terraform/issues

!!!!!!!!!!!!!!!!!!!!!!!!!!! TERRAFORM CRASH !!!!!!!!!!!!!!!!!!!!!!!!!!!!

[remilapeyre]

After testing with this configuration, it seems that the only resources to be subject to this bug are consul_intention, consul_node and consul_service:

resource "consul_agent_service" "app" {
  address = "www.google.com"
  name    = "google"
  port    = 80
  tags    = ["tag0", "tag1"]
}

resource "consul_catalog_entry" "app" {
  address = "192.168.10.10"
  node    = "foobar"

  service = {
    address = "127.0.0.1"
    id      = "redis1"
    name    = "redis"
    port    = 8000
    tags    = ["master", "v1"]
  }
}

resource "consul_intention" "database" {
  source_name      = "api"
  destination_name = "db"
  action           = "allow"
}

resource "consul_keys" "app" {
  # Set the CNAME of our load balancer as a key
  key {
    path  = "service/app/elb_address"
    value = "coucou"
  }
}

resource "consul_key_prefix" "myapp_config" {
  # Prefix to add to prepend to all of the subkey names below.
  path_prefix = "myapp/config/"

  subkeys = {
    "elb_cname"         = "coucou"
  }
}

resource "consul_node" "foobar" {
  address = "192.168.10.10"
  name    = "foobar"
}

resource "consul_prepared_query" "myapp-query" {
  name         = "myquery"
  only_passing = true
  near         = "_agent"

  service = "myapp"
  tags    = ["active", "!standby"]

  failover {
    nearest_n   = 3
    datacenters = ["us-west1", "us-east-2", "asia-east1"]
  }

  dns {
    ttl = "30s"
  }
}

resource "consul_service" "google" {
  name    = "google"
  node    = "${consul_node.compute.name}"
  port    = 80
  tags    = ["tag0"]
}

resource "consul_node" "compute" {
  name    = "compute-google"
  address = "www.google.com"
}

[remilapeyre]

Fixed by #69