Make bundle deploy work if no resources are defined (databricks#767)

## Changes

This PR sets "resource" to nil in the terraform representation if no
resources are defined in the bundle configuration. This solves two
problems:

1. Makes bundle deploy work without any resources specified. 
2. Previously if a `resources` block was removed after a deployment,
that would fail with an error. Now the resources would get destroyed as
expected.

Also removes `TerraformHasNoResources` which is no longer needed.

## Tests
New e2e tests.

bundle/bundle.go

@@ -38,10 +38,6 @@ type Bundle struct {
 	// Stores an initialized copy of this bundle's Terraform wrapper.
 	Terraform *tfexec.Terraform
 
-	// Indicates that the Terraform definition based on this bundle is empty,
-	// i.e. that it would deploy no resources.
-	TerraformHasNoResources bool
-
 	// Stores the locker responsible for acquiring/releasing a deployment lock.
 	Locker *locker.Locker
 

bundle/deploy/terraform/apply.go

@@ -16,10 +16,6 @@ func (w *apply) Name() string {
 }
 
 func (w *apply) Apply(ctx context.Context, b *bundle.Bundle) error {
-	if b.TerraformHasNoResources {
-		cmdio.LogString(ctx, "Note: there are no resources to deploy for this bundle")
-		return nil
-	}
 	tf := b.Terraform
 	if tf == nil {
 		return fmt.Errorf("terraform not initialized")

bundle/deploy/terraform/convert.go

@@ -49,7 +49,7 @@ func convPermission(ac resources.Permission) schema.ResourcePermissionsAccessCon
 //
 // NOTE: THIS IS CURRENTLY A HACK. WE NEED A BETTER WAY TO
 // CONVERT TO/FROM TERRAFORM COMPATIBLE FORMAT.
-func BundleToTerraform(config *config.Root) (*schema.Root, bool) {
+func BundleToTerraform(config *config.Root) *schema.Root {
 	tfroot := schema.NewRoot()
 	tfroot.Provider = schema.NewProviders()
 	tfroot.Resource = schema.NewResources()
@@ -174,7 +174,13 @@ func BundleToTerraform(config *config.Root) (*schema.Root, bool) {
 		}
 	}
 
-	return tfroot, noResources
+	// We explicitly set "resource" to nil to omit it from a JSON encoding.
+	// This is required because the terraform CLI requires >= 1 resources defined
+	// if the "resource" property is used in a .tf.json file.
+	if noResources {
+		tfroot.Resource = nil
+	}
+	return tfroot
 }
 
 func TerraformToBundle(state *tfjson.State, config *config.Root) error {

bundle/deploy/terraform/convert_test.go

@@ -51,7 +51,7 @@ func TestConvertJob(t *testing.T) {
 		},
 	}
 
-	out, _ := BundleToTerraform(&config)
+	out := BundleToTerraform(&config)
 	assert.Equal(t, "my job", out.Resource.Job["my_job"].Name)
 	assert.Len(t, out.Resource.Job["my_job"].JobCluster, 1)
 	assert.Equal(t, "https://github.com/foo/bar", out.Resource.Job["my_job"].GitSource.Url)
@@ -79,7 +79,7 @@ func TestConvertJobPermissions(t *testing.T) {
 		},
 	}
 
-	out, _ := BundleToTerraform(&config)
+	out := BundleToTerraform(&config)
 	assert.NotEmpty(t, out.Resource.Permissions["job_my_job"].JobId)
 	assert.Len(t, out.Resource.Permissions["job_my_job"].AccessControl, 1)
 
@@ -115,7 +115,7 @@ func TestConvertJobTaskLibraries(t *testing.T) {
 		},
 	}
 
-	out, _ := BundleToTerraform(&config)
+	out := BundleToTerraform(&config)
 	assert.Equal(t, "my job", out.Resource.Job["my_job"].Name)
 	require.Len(t, out.Resource.Job["my_job"].Task, 1)
 	require.Len(t, out.Resource.Job["my_job"].Task[0].Library, 1)
@@ -149,7 +149,7 @@ func TestConvertPipeline(t *testing.T) {
 		},
 	}
 
-	out, _ := BundleToTerraform(&config)
+	out := BundleToTerraform(&config)
 	assert.Equal(t, "my pipeline", out.Resource.Pipeline["my_pipeline"].Name)
 	assert.Len(t, out.Resource.Pipeline["my_pipeline"].Library, 2)
 	assert.Nil(t, out.Data)
@@ -173,7 +173,7 @@ func TestConvertPipelinePermissions(t *testing.T) {
 		},
 	}
 
-	out, _ := BundleToTerraform(&config)
+	out := BundleToTerraform(&config)
 	assert.NotEmpty(t, out.Resource.Permissions["pipeline_my_pipeline"].PipelineId)
 	assert.Len(t, out.Resource.Permissions["pipeline_my_pipeline"].AccessControl, 1)
 
@@ -208,7 +208,7 @@ func TestConvertModel(t *testing.T) {
 		},
 	}
 
-	out, _ := BundleToTerraform(&config)
+	out := BundleToTerraform(&config)
 	assert.Equal(t, "name", out.Resource.MlflowModel["my_model"].Name)
 	assert.Equal(t, "description", out.Resource.MlflowModel["my_model"].Description)
 	assert.Len(t, out.Resource.MlflowModel["my_model"].Tags, 2)
@@ -237,7 +237,7 @@ func TestConvertModelPermissions(t *testing.T) {
 		},
 	}
 
-	out, _ := BundleToTerraform(&config)
+	out := BundleToTerraform(&config)
 	assert.NotEmpty(t, out.Resource.Permissions["mlflow_model_my_model"].RegisteredModelId)
 	assert.Len(t, out.Resource.Permissions["mlflow_model_my_model"].AccessControl, 1)
 
@@ -261,7 +261,7 @@ func TestConvertExperiment(t *testing.T) {
 		},
 	}
 
-	out, _ := BundleToTerraform(&config)
+	out := BundleToTerraform(&config)
 	assert.Equal(t, "name", out.Resource.MlflowExperiment["my_experiment"].Name)
 	assert.Nil(t, out.Data)
 }
@@ -284,7 +284,7 @@ func TestConvertExperimentPermissions(t *testing.T) {
 		},
 	}
 
-	out, _ := BundleToTerraform(&config)
+	out := BundleToTerraform(&config)
 	assert.NotEmpty(t, out.Resource.Permissions["mlflow_experiment_my_experiment"].ExperimentId)
 	assert.Len(t, out.Resource.Permissions["mlflow_experiment_my_experiment"].AccessControl, 1)
 
@@ -327,7 +327,7 @@ func TestConvertModelServing(t *testing.T) {
 		},
 	}
 
-	out, _ := BundleToTerraform(&config)
+	out := BundleToTerraform(&config)
 	resource := out.Resource.ModelServing["my_model_serving_endpoint"]
 	assert.Equal(t, "name", resource.Name)
 	assert.Equal(t, "model_name", resource.Config.ServedModels[0].ModelName)
@@ -357,7 +357,7 @@ func TestConvertModelServingPermissions(t *testing.T) {
 		},
 	}
 
-	out, _ := BundleToTerraform(&config)
+	out := BundleToTerraform(&config)
 	assert.NotEmpty(t, out.Resource.Permissions["model_serving_my_model_serving_endpoint"].ServingEndpointId)
 	assert.Len(t, out.Resource.Permissions["model_serving_my_model_serving_endpoint"].AccessControl, 1)
 

bundle/deploy/terraform/write.go

@@ -21,8 +21,7 @@ func (w *write) Apply(ctx context.Context, b *bundle.Bundle) error {
 		return err
 	}
 
-	root, noResources := BundleToTerraform(&b.Config)
-	b.TerraformHasNoResources = noResources
+	root := BundleToTerraform(&b.Config)
 	f, err := os.Create(filepath.Join(dir, "bundle.tf.json"))
 	if err != nil {
 		return err

internal/bundle/bundles/deploy_then_remove_resources/databricks_template_schema.json

@@ -0,0 +1,8 @@
+{
+    "properties": {
+        "unique_id": {
+            "type": "string",
+            "description": "Unique ID for job name"
+        }
+    }
+}

internal/bundle/bundles/deploy_then_remove_resources/template/databricks.yml.tmpl

@@ -0,0 +1,8 @@
+bundle:
+  name: deploy-then-remove
+
+workspace:
+  root_path: "~/.bundle/{{.unique_id}}"
+
+include:
+  - "./*.yml"

internal/bundle/bundles/deploy_then_remove_resources/template/foo.py

@@ -0,0 +1 @@
+print("hello")

internal/bundle/bundles/deploy_then_remove_resources/template/resources.yml.tmpl

@@ -0,0 +1,7 @@
+resources:
+  pipelines:
+    bar:
+      name: test-bundle-pipeline-{{.unique_id}}
+      libraries:
+        - notebook:
+          path: "./foo.py"

internal/bundle/bundles/empty_bundle/databricks.yml

@@ -0,0 +1,2 @@
+bundle:
+  name: abc

internal/bundle/deploy_then_remove_resources_test.go

@@ -0,0 +1,55 @@
+package bundle
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/databricks/cli/internal"
+	"github.com/databricks/databricks-sdk-go"
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestAccBundleDeployThenRemoveResources(t *testing.T) {
+	env := internal.GetEnvOrSkipTest(t, "CLOUD_ENV")
+	t.Log(env)
+
+	uniqueId := uuid.New().String()
+	bundleRoot, err := initTestTemplate(t, "deploy_then_remove_resources", map[string]any{
+		"unique_id": uniqueId,
+	})
+	require.NoError(t, err)
+
+	// deploy pipeline
+	err = deployBundle(t, bundleRoot)
+	require.NoError(t, err)
+
+	w, err := databricks.NewWorkspaceClient()
+	require.NoError(t, err)
+
+	// assert pipeline is created
+	pipelineName := "test-bundle-pipeline-" + uniqueId
+	pipeline, err := w.Pipelines.GetByName(context.Background(), pipelineName)
+	require.NoError(t, err)
+	assert.Equal(t, pipeline.Name, pipelineName)
+
+	// delete resources.yml
+	err = os.Remove(filepath.Join(bundleRoot, "resources.yml"))
+	require.NoError(t, err)
+
+	// deploy again
+	err = deployBundle(t, bundleRoot)
+	require.NoError(t, err)
+
+	// assert pipeline is deleted
+	_, err = w.Pipelines.GetByName(context.Background(), pipelineName)
+	assert.ErrorContains(t, err, "does not exist")
+
+	t.Cleanup(func() {
+		err = destroyBundle(t, bundleRoot)
+		require.NoError(t, err)
+	})
+}

internal/bundle/empty_bundle_test.go

@@ -0,0 +1,37 @@
+package bundle
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/databricks/cli/internal"
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/require"
+)
+
+func TestAccEmptyBundleDeploy(t *testing.T) {
+	env := internal.GetEnvOrSkipTest(t, "CLOUD_ENV")
+	t.Log(env)
+
+	// create empty bundle
+	tmpDir := t.TempDir()
+	f, err := os.Create(filepath.Join(tmpDir, "databricks.yml"))
+	require.NoError(t, err)
+
+	bundleRoot := fmt.Sprintf(`bundle:
+  name: %s`, uuid.New().String())
+	_, err = f.WriteString(bundleRoot)
+	require.NoError(t, err)
+	f.Close()
+
+	// deploy empty bundle
+	err = deployBundle(t, tmpDir)
+	require.NoError(t, err)
+
+	t.Cleanup(func() {
+		err = destroyBundle(t, tmpDir)
+		require.NoError(t, err)
+	})
+}