core: Separate resource lifecycle for data vs. managed resources

The key difference between data and managed resources is in their
respective lifecycles. Now the expanded resource EvalTree switches on
the resource mode, generating a different lifecycle for each mode.

For this initial change only managed resources are implemented, using the
same implementation as before; data resources are no-ops. The data
resource implementation will follow in a subsequent change.

terraform/transform_resource.go

@@ -195,10 +195,8 @@ func (n *graphNodeExpandedResource) StateDependencies() []string {
 
 // GraphNodeEvalable impl.
 func (n *graphNodeExpandedResource) EvalTree() EvalNode {
-	var diff *InstanceDiff
 	var provider ResourceProvider
 	var resourceConfig *ResourceConfig
-	var state *InstanceState
 
 	// Build the resource. If we aren't part of a multi-resource, then
 	// we still consider ourselves as count index zero.
@@ -259,8 +257,34 @@ func (n *graphNodeExpandedResource) EvalTree() EvalNode {
 	info := n.instanceInfo()
 	seq.Nodes = append(seq.Nodes, &EvalInstanceInfo{Info: info})
 
+	// Each resource mode has its own lifecycle
+	switch n.Resource.Mode {
+	case config.ManagedResourceMode:
+		seq.Nodes = append(
+			seq.Nodes,
+			n.managedResourceEvalNodes(resource, info, resourceConfig)...,
+		)
+	case config.DataResourceMode:
+		seq.Nodes = append(
+			seq.Nodes,
+			n.dataResourceEvalNodes(resource, info, resourceConfig)...,
+		)
+	default:
+		panic(fmt.Errorf("unsupported resource mode %s", n.Resource.Mode))
+	}
+
+	return seq
+}
+
+func (n *graphNodeExpandedResource) managedResourceEvalNodes(resource *Resource, info *InstanceInfo, resourceConfig *ResourceConfig) []EvalNode {
+	var diff *InstanceDiff
+	var provider ResourceProvider
+	var state *InstanceState
+
+	nodes := make([]EvalNode, 0, 5)
+
 	// Refresh the resource
-	seq.Nodes = append(seq.Nodes, &EvalOpFilter{
+	nodes = append(nodes, &EvalOpFilter{
 		Ops: []walkOperation{walkRefresh},
 		Node: &EvalSequence{
 			Nodes: []EvalNode{
@@ -290,7 +314,7 @@ func (n *graphNodeExpandedResource) EvalTree() EvalNode {
 	})
 
 	// Diff the resource
-	seq.Nodes = append(seq.Nodes, &EvalOpFilter{
+	nodes = append(nodes, &EvalOpFilter{
 		Ops: []walkOperation{walkPlan},
 		Node: &EvalSequence{
 			Nodes: []EvalNode{
@@ -343,7 +367,7 @@ func (n *graphNodeExpandedResource) EvalTree() EvalNode {
 	})
 
 	// Diff the resource for destruction
-	seq.Nodes = append(seq.Nodes, &EvalOpFilter{
+	nodes = append(nodes, &EvalOpFilter{
 		Ops: []walkOperation{walkPlanDestroy},
 		Node: &EvalSequence{
 			Nodes: []EvalNode{
@@ -374,7 +398,7 @@ func (n *graphNodeExpandedResource) EvalTree() EvalNode {
 	var createNew, tainted bool
 	var createBeforeDestroyEnabled bool
 	var wasChangeType DiffChangeType
-	seq.Nodes = append(seq.Nodes, &EvalOpFilter{
+	nodes = append(nodes, &EvalOpFilter{
 		Ops: []walkOperation{walkApply, walkDestroy},
 		Node: &EvalSequence{
 			Nodes: []EvalNode{
@@ -557,7 +581,17 @@ func (n *graphNodeExpandedResource) EvalTree() EvalNode {
 		},
 	})
 
-	return seq
+	return nodes
+}
+
+func (n *graphNodeExpandedResource) dataResourceEvalNodes(resource *Resource, info *InstanceInfo, resourceConfig *ResourceConfig) []EvalNode {
+	//var diff *InstanceDiff
+	//var provider ResourceProvider
+	//var state *InstanceState
+
+	nodes := make([]EvalNode, 0, 5)
+
+	return nodes
 }
 
 // instanceInfo is used for EvalTree.