From f8b1a3c7a4134bee662dd94ec78882c88651858a Mon Sep 17 00:00:00 2001
From: James Bardin <j.bardin@gmail.com>
Date: Mon, 15 Oct 2018 21:13:05 -0400
Subject: [PATCH] make sure apply can properly destroy

We need to ensure that a destroyed value is returned as such from apply
---
 helper/plugin/grpc_provider.go | 47 ++++++++++++++++++++++++----------
 1 file changed, 34 insertions(+), 13 deletions(-)

diff --git a/helper/plugin/grpc_provider.go b/helper/plugin/grpc_provider.go
index 83ab81f84..d99e8bb29 100644
--- a/helper/plugin/grpc_provider.go
+++ b/helper/plugin/grpc_provider.go
@@ -496,10 +496,23 @@ func (s *GRPCProviderServer) ApplyResourceChange(_ context.Context, req *proto.A
 		}
 	}
 
-	diff, err := schema.DiffFromValues(priorStateVal, plannedStateVal, res)
-	if err != nil {
-		resp.Diagnostics = convert.AppendProtoDiag(resp.Diagnostics, err)
-		return resp, nil
+	var diff *terraform.InstanceDiff
+	destroy := false
+
+	// a null state means we are destroying the instance
+	if plannedStateVal.IsNull() {
+		destroy = true
+		diff = &terraform.InstanceDiff{
+			Attributes: make(map[string]*terraform.ResourceAttrDiff),
+			Meta:       make(map[string]interface{}),
+			Destroy:    true,
+		}
+	} else {
+		diff, err = schema.DiffFromValues(priorStateVal, plannedStateVal, res)
+		if err != nil {
+			resp.Diagnostics = convert.AppendProtoDiag(resp.Diagnostics, err)
+			return resp, nil
+		}
 	}
 
 	if diff == nil {
@@ -516,10 +529,16 @@ func (s *GRPCProviderServer) ApplyResourceChange(_ context.Context, req *proto.A
 		return resp, nil
 	}
 
-	newStateVal, err := schema.StateValueFromInstanceState(newInstanceState, block.ImpliedType())
-	if err != nil {
-		resp.Diagnostics = convert.AppendProtoDiag(resp.Diagnostics, err)
-		return resp, nil
+	newStateVal := cty.NullVal(block.ImpliedType())
+
+	// We keep the null val if we destroyed the resource, otherwise build the
+	// entire object, even if the new state was nil.
+	if !destroy {
+		newStateVal, err = schema.StateValueFromInstanceState(newInstanceState, block.ImpliedType())
+		if err != nil {
+			resp.Diagnostics = convert.AppendProtoDiag(resp.Diagnostics, err)
+			return resp, nil
+		}
 	}
 
 	newStateMP, err := msgpack.Marshal(newStateVal, block.ImpliedType())
@@ -531,12 +550,14 @@ func (s *GRPCProviderServer) ApplyResourceChange(_ context.Context, req *proto.A
 		Msgpack: newStateMP,
 	}
 
-	meta, err := json.Marshal(newInstanceState.Meta)
-	if err != nil {
-		resp.Diagnostics = convert.AppendProtoDiag(resp.Diagnostics, err)
-		return resp, nil
+	if newInstanceState != nil {
+		meta, err := json.Marshal(newInstanceState.Meta)
+		if err != nil {
+			resp.Diagnostics = convert.AppendProtoDiag(resp.Diagnostics, err)
+			return resp, nil
+		}
+		resp.Private = meta
 	}
-	resp.Private = meta
 
 	return resp, nil
 }