From 082f91cd85339cdca015dc647b830b5554f2f366 Mon Sep 17 00:00:00 2001
From: James Bardin <j.bardin@gmail.com>
Date: Thu, 21 May 2020 21:53:36 -0400
Subject: [PATCH] fix ModulePath for nodeExpandModule

ModulePath was incorrectly returning the parent module, because it did
not implement ReferenceOutside. With ReferenceOutside working correctly,
we can have ModulePath return the real path and remove the special case
for this during pruning.
---
 terraform/node_module_expand.go         | 14 ++++++++++----
 terraform/transform_destroy_edge.go     |  3 ---
 terraform/transform_module_expansion.go | 18 +++++++++++++++---
 3 files changed, 25 insertions(+), 10 deletions(-)

diff --git a/terraform/node_module_expand.go b/terraform/node_module_expand.go
index 5168508ee0..676a230498 100644
--- a/terraform/node_module_expand.go
+++ b/terraform/node_module_expand.go
@@ -21,9 +21,10 @@ type nodeExpandModule struct {
 }
 
 var (
-	_ RemovableIfNotTargeted = (*nodeExpandModule)(nil)
-	_ GraphNodeEvalable      = (*nodeExpandModule)(nil)
-	_ GraphNodeReferencer    = (*nodeExpandModule)(nil)
+	_ RemovableIfNotTargeted    = (*nodeExpandModule)(nil)
+	_ GraphNodeEvalable         = (*nodeExpandModule)(nil)
+	_ GraphNodeReferencer       = (*nodeExpandModule)(nil)
+	_ GraphNodeReferenceOutside = (*nodeExpandModule)(nil)
 
 	// modules both record their expansion, and require expansion from their
 	// parent modules.
@@ -48,7 +49,7 @@ func (n *nodeExpandModule) ModulePath() addrs.Module {
 	// This node represents the module call within a module,
 	// so return the CallerAddr as the path as the module
 	// call may expand into multiple child instances
-	return n.Addr.Parent()
+	return n.Addr
 }
 
 // GraphNodeReferencer implementation
@@ -94,6 +95,11 @@ func (n *nodeExpandModule) References() []*addrs.Reference {
 	return appendResourceDestroyReferences(refs)
 }
 
+// GraphNodeReferenceOutside
+func (n *nodeExpandModule) ReferenceOutside() (selfPath, referencePath addrs.Module) {
+	return n.Addr, n.Addr.Parent()
+}
+
 // RemovableIfNotTargeted implementation
 func (n *nodeExpandModule) RemoveIfNotTargeted() bool {
 	// We need to add this so that this node will be removed if
diff --git a/terraform/transform_destroy_edge.go b/terraform/transform_destroy_edge.go
index 0d9a06ddf4..226a0162e5 100644
--- a/terraform/transform_destroy_edge.go
+++ b/terraform/transform_destroy_edge.go
@@ -187,9 +187,6 @@ func (t *pruneUnusedNodesTransformer) Transform(g *Graph) error {
 	for _, v := range g.Vertices() {
 		var path addrs.Module
 		switch v := v.(type) {
-		case instanceExpander:
-			path = v.expandsInstances()
-
 		case GraphNodeModulePath:
 			path = v.ModulePath()
 		default:
diff --git a/terraform/transform_module_expansion.go b/terraform/transform_module_expansion.go
index e6c961c324..d1d4185e55 100644
--- a/terraform/transform_module_expansion.go
+++ b/terraform/transform_module_expansion.go
@@ -3,6 +3,7 @@ package terraform
 import (
 	"log"
 
+	"github.com/hashicorp/terraform/addrs"
 	"github.com/hashicorp/terraform/configs"
 	"github.com/hashicorp/terraform/dag"
 )
@@ -105,11 +106,22 @@ func (t *ModuleExpansionTransformer) transform(g *Graph, c *configs.Config, pare
 	t.closers[c.Path.String()] = closer
 
 	for _, childV := range g.Vertices() {
-		pather, ok := childV.(GraphNodeModulePath)
-		if !ok {
+		// don't connect a node to itself
+		if childV == v {
 			continue
 		}
-		if pather.ModulePath().Equal(c.Path) {
+
+		var path addrs.Module
+		switch t := childV.(type) {
+		case GraphNodeModulePath:
+			path = t.ModulePath()
+		case GraphNodeReferenceOutside:
+			path, _ = t.ReferenceOutside()
+		default:
+			continue
+		}
+
+		if path.Equal(c.Path) {
 			log.Printf("[TRACE] ModuleExpansionTransformer: %s must wait for expansion of %s", dag.VertexName(childV), c.Path)
 			g.Connect(dag.BasicEdge(childV, v))
 		}