Allow named root for better recognition in logs

internal/dag/graph.go

@@ -117,6 +117,26 @@ func (g *Graph) Add(v Vertex) Vertex {
 	return v
 }
 
+// AddRoot adds a root vertex to the graph and connects all vertices that do not
+// already depend on at least one other node to the root node.
+func (g *Graph) AddRoot(root Vertex) Vertex {
+	g.init()
+	g.Add(root)
+
+	// Everything that doesn't already depend on at least one other node will
+	// depend on the root node, except the root node itself.
+	for v := range g.VerticesSeq() {
+		if v == Vertex(root) {
+			continue
+		}
+
+		if g.UpEdges(v).Len() == 0 {
+			g.Connect(BasicEdge(root, v))
+		}
+	}
+	return root
+}
+
 // Remove removes a vertex from the graph. This will also remove any
 // edges with this vertex as a source or target.
 func (g *Graph) Remove(v Vertex) Vertex {

internal/terraform/graph.go

@@ -168,9 +168,10 @@ func (g *Graph) walk(walker GraphWalker) tfdiags.Diagnostics {
 					return
 				}
 				// If we passed validation then there is exactly one root node.
-				// That root node should always be "rootNode", the singleton
-				// root node value.
-				if n, err := g.Root(); err != nil || n != dag.Vertex(rootNode) {
+				// That root node should always be a type of "graphNodeRoot".
+				n, err := g.Root()
+				_, isRoot := n.(graphNodeRoot)
+				if err != nil || !isRoot {
 					diags = diags.Append(tfdiags.Sourceless(
 						tfdiags.Error,
 						"Graph node has invalid dynamic subgraph",

internal/terraform/node_policy_eval.go

@@ -29,7 +29,7 @@ func (n *nodePolicyEval) DynamicExpand(ctx EvalContext) (*Graph, tfdiags.Diagnos
 		return nil, nil
 	}
 	// ensure the graph has a single root
-	addRootNodeToGraph(&policyGraph.graph)
+	policyGraph.graph.AddRoot(graphNodeRoot{"policy"})
 	return &policyGraph.graph, nil
 }
 

internal/terraform/transform_root.go

@@ -4,6 +4,8 @@
 package terraform
 
 import (
+	"fmt"
+
 	"github.com/hashicorp/terraform/internal/dag"
 )
 
@@ -30,22 +32,12 @@ func addRootNodeToGraph(g *Graph) {
 	// Note that rootNode is intentionally added by value and not by pointer
 	// so that all root nodes will be equal to one another and therefore
 	// coalesce when two valid graphs get merged together into a single graph.
-	g.Add(rootNode)
-
-	// Everything that doesn't already depend on at least one other node will
-	// depend on the root node, except the root node itself.
-	for _, v := range g.Vertices() {
-		if v == dag.Vertex(rootNode) {
-			continue
-		}
-
-		if g.UpEdges(v).Len() == 0 {
-			g.Connect(dag.BasicEdge(rootNode, v))
-		}
-	}
+	g.AddRoot(rootNode)
 }
 
-type graphNodeRoot struct{}
+type graphNodeRoot struct {
+	Prefix string
+}
 
 // rootNode is the singleton value representing all root graph nodes.
 //
@@ -56,7 +48,10 @@ type graphNodeRoot struct{}
 var rootNode graphNodeRoot
 
 func (n graphNodeRoot) Name() string {
-	return rootNodeName
+	if n.Prefix == "" {
+		return rootNodeName
+	}
+	return fmt.Sprintf("%s.%s", rootNodeName, n.Prefix)
 }
 
 // CloseRootModuleTransformer is a GraphTransformer that adds a root to the graph.