Fix metadata computation for empty bundle (#939)

## Changes
This PR fixes metadata computation for empty bundle. Before we would
error because the `terraform.Load()` mutator errors on a empty / no
state file.

## Tests
Failing integration tests now pass.

bundle/deploy/terraform/convert.go

@@ -213,6 +213,11 @@ func BundleToTerraform(config *config.Root) *schema.Root {
 }
 
 func TerraformToBundle(state *tfjson.State, config *config.Root) error {
+	// This is a no-op if the state is empty.
+	if state.Values == nil || state.Values.RootModule == nil {
+		return nil
+	}
+
 	for _, resource := range state.Values.RootModule.Resources {
 		// Limit to resources.
 		if resource.Mode != tfjson.ManagedResourceMode {

bundle/deploy/terraform/load.go

@@ -3,13 +3,20 @@ package terraform
 import (
 	"context"
 	"fmt"
+	"slices"
 
 	"github.com/databricks/cli/bundle"
 	"github.com/hashicorp/terraform-exec/tfexec"
 	tfjson "github.com/hashicorp/terraform-json"
 )
 
-type load struct{}
+type loadMode int
+
+const ErrorOnEmptyState loadMode = 0
+
+type load struct {
+	modes []loadMode
+}
 
 func (l *load) Name() string {
 	return "terraform.Load"
@@ -31,7 +38,7 @@ func (l *load) Apply(ctx context.Context, b *bundle.Bundle) error {
 		return err
 	}
 
-	err = ValidateState(state)
+	err = l.validateState(state)
 	if err != nil {
 		return err
 	}
@@ -45,10 +52,13 @@ func (l *load) Apply(ctx context.Context, b *bundle.Bundle) error {
 	return nil
 }
 
-func ValidateState(state *tfjson.State) error {
+func (l *load) validateState(state *tfjson.State) error {
 	if state.Values == nil {
+		if slices.Contains(l.modes, ErrorOnEmptyState) {
 			return fmt.Errorf("no deployment state. Did you forget to run 'databricks bundle deploy'?")
 		}
+		return nil
+	}
 
 	if state.Values.RootModule == nil {
 		return fmt.Errorf("malformed terraform state: RootModule not set")
@@ -57,6 +67,6 @@ func ValidateState(state *tfjson.State) error {
 	return nil
 }
 
-func Load() bundle.Mutator {
+func Load(modes ...loadMode) bundle.Mutator {
-	return &load{}
+	return &load{modes: modes}
 }

bundle/deploy/terraform/load_test.go

@@ -34,7 +34,7 @@ func TestLoadWithNoState(t *testing.T) {
 
 	err = bundle.Apply(context.Background(), b, bundle.Seq(
 		Initialize(),
-		Load(),
+		Load(ErrorOnEmptyState),
 	))
 
 	require.ErrorContains(t, err, "Did you forget to run 'databricks bundle deploy'")

cmd/bundle/run.go

@@ -38,7 +38,7 @@ func newRunCommand() *cobra.Command {
 			terraform.Interpolate(),
 			terraform.Write(),
 			terraform.StatePull(),
-			terraform.Load(),
+			terraform.Load(terraform.ErrorOnEmptyState),
 		))
 		if err != nil {
 			return err