From a7342de274d4d498538131f3dd338a65f6fce74b Mon Sep 17 00:00:00 2001
From: Martin Atkins <mart@degeneration.co.uk>
Date: Mon, 27 Aug 2018 17:34:14 -0700
Subject: [PATCH] core: Properly handle no-op changes in plan

Previously we just left these out of the plan altogether, but in the new
plan types we intentionally include change information for every resource
instance, even if no changes are actually planned, to allow alternative
plan file viewers to show what isn't changing as well as what is.
---
 command/format/plan.go         |  2 ++
 helper/plugin/grpc_provider.go |  9 +++++++++
 plugin/grpc_provider.go        | 17 +++++++++++------
 terraform/transform_diff.go    |  2 ++
 4 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/command/format/plan.go b/command/format/plan.go
index a2a49c303..e02190f9e 100644
--- a/command/format/plan.go
+++ b/command/format/plan.go
@@ -91,6 +91,8 @@ func NewPlan(changes *plans.Changes) *Plan {
 		}
 
 		switch rc.Action {
+		case plans.NoOp:
+			continue
 		case plans.Create:
 			if dataSource {
 				// Use "refresh" as the action for display, but core
diff --git a/helper/plugin/grpc_provider.go b/helper/plugin/grpc_provider.go
index 0c8417460..be3bbc61f 100644
--- a/helper/plugin/grpc_provider.go
+++ b/helper/plugin/grpc_provider.go
@@ -386,6 +386,15 @@ func (s *GRPCProviderServer) PlanResourceChange(_ context.Context, req *proto.Pl
 		return resp, nil
 	}
 
+	if diff == nil {
+		// schema.Provider.Diff returns nil if it ends up making a diff with
+		// no changes, but our new interface wants us to return an actual
+		// change description that _shows_ there are no changes, so we need
+		// to synthesize one here.
+		resp.PlannedState = req.PriorState
+		return resp, nil
+	}
+
 	// now we need to apply the diff to the prior state, so get the planned state
 	plannedStateVal, err := schema.ApplyDiff(priorStateVal, diff, block)
 	if err != nil {
diff --git a/plugin/grpc_provider.go b/plugin/grpc_provider.go
index 6d8cfe65c..3b066258d 100644
--- a/plugin/grpc_provider.go
+++ b/plugin/grpc_provider.go
@@ -6,6 +6,8 @@ import (
 	"log"
 	"sync"
 
+	"github.com/zclconf/go-cty/cty"
+
 	plugin "github.com/hashicorp/go-plugin"
 	"github.com/hashicorp/terraform/plugin/convert"
 	"github.com/hashicorp/terraform/plugin/proto"
@@ -398,14 +400,17 @@ func (p *GRPCProvider) ApplyResourceChange(r providers.ApplyResourceChangeReques
 
 	resp.Private = protoResp.Private
 
-	state, err := msgpack.Unmarshal(protoResp.NewState.Msgpack, resSchema.Block.ImpliedType())
-	if err != nil {
-		resp.Diagnostics = resp.Diagnostics.Append(err)
-		return resp
+	if protoResp.NewState != nil {
+		state, err := msgpack.Unmarshal(protoResp.NewState.Msgpack, resSchema.Block.ImpliedType())
+		if err != nil {
+			resp.Diagnostics = resp.Diagnostics.Append(err)
+			return resp
+		}
+		resp.NewState = state
+	} else {
+		resp.NewState = cty.NullVal(resSchema.Block.ImpliedType())
 	}
 
-	resp.NewState = state
-
 	return resp
 }
 
diff --git a/terraform/transform_diff.go b/terraform/transform_diff.go
index 67a94fed9..f22c17f7b 100644
--- a/terraform/transform_diff.go
+++ b/terraform/transform_diff.go
@@ -34,6 +34,8 @@ func (t *DiffTransformer) Transform(g *Graph) error {
 		// other actions.
 		var update, delete bool
 		switch rc.Action {
+		case plans.NoOp:
+			continue
 		case plans.Delete:
 			delete = true
 		case plans.Replace: