terraform: only omit vars on full destroys

terraform/graph_builder.go

@@ -153,7 +153,7 @@ func (b *BuiltinGraphBuilder) Steps(path []string) []GraphTransformer {
 	if len(path) <= 1 {
 		steps = append(steps,
 			// Create the destruction nodes
-			&DestroyTransformer{},
+			&DestroyTransformer{FullDestroy: b.Destroy},
 			&CreateBeforeDestroyTransformer{},
 			b.conditional(&conditionalOpts{
 				If:   func() bool { return !b.Verbose },

terraform/graph_config_node_output.go

@@ -62,7 +62,7 @@ func (n *GraphNodeConfigOutput) Proxy() bool {
 }
 
 // GraphNodeDestroyEdgeInclude impl.
-func (n *GraphNodeConfigOutput) DestroyEdgeInclude() bool {
+func (n *GraphNodeConfigOutput) DestroyEdgeInclude(bool) bool {
 	return false
 }
 

terraform/graph_config_node_variable.go

@@ -56,11 +56,14 @@ func (n *GraphNodeConfigVariable) VariableName() string {
 }
 
 // GraphNodeDestroyEdgeInclude impl.
-func (n *GraphNodeConfigVariable) DestroyEdgeInclude() bool {
+func (n *GraphNodeConfigVariable) DestroyEdgeInclude(full bool) bool {
 	// Don't include variables as dependencies in destroy nodes.
 	// Destroy nodes don't interpolate anyways and this has a possibility
 	// to create cycles. See GH-1835
-	return false
+	//
+	// We include the variable on non-full destroys because it might
+	// be used for count interpolation.
+	return !full
 }
 
 // GraphNodeProxy impl.

terraform/transform_destroy.go

@@ -49,12 +49,14 @@ type GraphNodeDestroyPrunable interface {
 // as an edge within the destroy graph. This is usually done because it
 // might cause unnecessary cycles.
 type GraphNodeDestroyEdgeInclude interface {
-	DestroyEdgeInclude() bool
+	DestroyEdgeInclude(bool) bool
 }
 
 // DestroyTransformer is a GraphTransformer that creates the destruction
 // nodes for things that _might_ be destroyed.
-type DestroyTransformer struct{}
+type DestroyTransformer struct {
+	FullDestroy bool
+}
 
 func (t *DestroyTransformer) Transform(g *Graph) error {
 	var connect, remove []dag.Edge
@@ -111,7 +113,8 @@ func (t *DestroyTransformer) transform(
 		for _, edgeRaw := range downEdges {
 			// If this thing specifically requests to not be depended on
 			// by destroy nodes, then don't.
-			if i, ok := edgeRaw.(GraphNodeDestroyEdgeInclude); ok && !i.DestroyEdgeInclude() {
+			if i, ok := edgeRaw.(GraphNodeDestroyEdgeInclude); ok &&
+				!i.DestroyEdgeInclude(t.FullDestroy) {
 				continue
 			}