terraform: Don't panic when visiting ephemeral resource nodes

We don't yet do anything useful when we get there, but we do at least fail
in a vaguely-graceful way.

internal/terraform/node_resource_plan_instance.go

@@ -75,6 +75,8 @@ func (n *NodePlannableResourceInstance) Execute(ctx EvalContext, op walkOperatio
 		return n.managedResourceExecute(ctx)
 	case addrs.DataResourceMode:
 		return n.dataResourceExecute(ctx)
+	case addrs.EphemeralResourceMode:
+		return n.ephemeralResourceExecute(ctx)
 	default:
 		panic(fmt.Errorf("unsupported resource mode %s", n.Config.Mode))
 	}
@@ -443,6 +445,23 @@ func (n *NodePlannableResourceInstance) managedResourceExecute(ctx EvalContext)
 	return diags
 }
 
+func (n *NodePlannableResourceInstance) ephemeralResourceExecute(ctx EvalContext) (diags tfdiags.Diagnostics) {
+	config := n.Config
+	addr := n.ResourceInstanceAddr()
+	var diagRng *hcl.Range
+	if config != nil {
+		diagRng = config.DeclRange.Ptr()
+	}
+
+	diags = diags.Append(&hcl.Diagnostic{
+		Severity: hcl.DiagError,
+		Summary:  "Ephemeral resources not yet supported",
+		Detail:   fmt.Sprintf("There is not yet any implementation of planning for %s.", addr),
+		Subject:  diagRng,
+	})
+	return diags
+}
+
 // replaceTriggered checks if this instance needs to be replace due to a change
 // in a replace_triggered_by reference. If replacement is required, the
 // instance address is added to forceReplace

internal/terraform/transform_attach_config_resource.go

@@ -89,6 +89,35 @@ func (t *AttachResourceConfigTransformer) Transform(g *Graph) error {
 			log.Printf("[TRACE] AttachResourceConfigTransformer: attaching to %q (%T) config from %#v", dag.VertexName(v), v, r.DeclRange)
 			arn.AttachResourceConfig(r)
 
+			// attach the provider_meta info
+			if gnapmc, ok := v.(GraphNodeAttachProviderMetaConfigs); ok {
+				log.Printf("[TRACE] AttachResourceConfigTransformer: attaching provider meta configs to %s", dag.VertexName(v))
+				if config == nil {
+					log.Printf("[TRACE] AttachResourceConfigTransformer: no config set on the transformer for %s", dag.VertexName(v))
+					continue
+				}
+				if config.Module == nil {
+					log.Printf("[TRACE] AttachResourceConfigTransformer: no module in config for %s", dag.VertexName(v))
+					continue
+				}
+				if config.Module.ProviderMetas == nil {
+					log.Printf("[TRACE] AttachResourceConfigTransformer: no provider metas defined for %s", dag.VertexName(v))
+					continue
+				}
+				gnapmc.AttachProviderMetaConfigs(config.Module.ProviderMetas)
+			}
+		}
+		for _, r := range config.Module.EphemeralResources {
+			rAddr := r.Addr()
+
+			if rAddr != addr.Resource {
+				// Not the same resource
+				continue
+			}
+
+			log.Printf("[TRACE] AttachResourceConfigTransformer: attaching to %q (%T) config from %#v", dag.VertexName(v), v, r.DeclRange)
+			arn.AttachResourceConfig(r)
+
 			// attach the provider_meta info
 			if gnapmc, ok := v.(GraphNodeAttachProviderMetaConfigs); ok {
 				log.Printf("[TRACE] AttachResourceConfigTransformer: attaching provider meta configs to %s", dag.VertexName(v))