Improved error message when 'bricks bundle run' is executed before 'bricks bundle deploy' (#378)

## Changes
Improved error message when 'bricks bundle run' is executed before
'bricks bundle deploy'

The error happens when we attempt to load terraform state when it does
not exist.

The best way to check if terraform state actually exists is to call
`terraform show -json` and that's what already happens here

https://github.com/databricks/bricks/compare/main...error-before-deploy#diff-8c50f8c04e568397bc865b7e02d1f4ec5b18379d8d32daddfeb041035d804f5fL28

Absence of `state.Values` indicates that there is no state and likely
bundle was just never deployed.

## Tests
Ran `bricks bundle run test_job` on a new non-deployed bundle.

**Output:**

`Error: terraform show: No state. Did you forget to run 'bricks bundle
deploy'?`

Running `bricks bundle deploy && bricks bundle run test_job` succeeds.

---------

Co-authored-by: Pieter Noordhuis <pieter.noordhuis@databricks.com>

bundle/deploy/terraform/convert.go

@@ -154,14 +154,6 @@ func BundleToTerraform(config *config.Root) *schema.Root {
 }
 
 func TerraformToBundle(state *tfjson.State, config *config.Root) error {
-	if state.Values == nil {
-		return fmt.Errorf("state.Values not set")
-	}
-
-	if state.Values.RootModule == nil {
-		return fmt.Errorf("state.Values.RootModule not set")
-	}
-
 	for _, resource := range state.Values.RootModule.Resources {
 		// Limit to resources.
 		if resource.Mode != tfjson.ManagedResourceMode {

bundle/deploy/terraform/load.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/databricks/bricks/bundle"
 	"github.com/hashicorp/terraform-exec/tfexec"
+	tfjson "github.com/hashicorp/terraform-json"
 )
 
 type load struct{}
@@ -30,6 +31,11 @@ func (l *load) Apply(ctx context.Context, b *bundle.Bundle) ([]bundle.Mutator, e
 		return nil, err
 	}
 
+	err = ValidateState(state)
+	if err != nil {
+		return nil, err
+	}
+
 	// Merge state into configuration.
 	err = TerraformToBundle(state, &b.Config)
 	if err != nil {
@@ -39,6 +45,18 @@ func (l *load) Apply(ctx context.Context, b *bundle.Bundle) ([]bundle.Mutator, e
 	return nil, nil
 }
 
+func ValidateState(state *tfjson.State) error {
+	if state.Values == nil {
+		return fmt.Errorf("no deployment state. Did you forget to run 'bricks bundle deploy'?")
+	}
+
+	if state.Values.RootModule == nil {
+		return fmt.Errorf("malformed terraform state: RootModule not set")
+	}
+
+	return nil
+}
+
 func Load() bundle.Mutator {
 	return &load{}
 }

bundle/deploy/terraform/load_test.go

@@ -0,0 +1,41 @@
+package terraform
+
+import (
+	"context"
+	"os/exec"
+	"testing"
+
+	"github.com/databricks/bricks/bundle"
+	"github.com/databricks/bricks/bundle/config"
+	"github.com/stretchr/testify/require"
+)
+
+func TestLoadWithNoState(t *testing.T) {
+	_, err := exec.LookPath("terraform")
+	if err != nil {
+		t.Skipf("cannot find terraform binary: %s", err)
+	}
+
+	b := &bundle.Bundle{
+		Config: config.Root{
+			Path: t.TempDir(),
+			Bundle: config.Bundle{
+				Environment: "whatever",
+				Terraform: &config.Terraform{
+					ExecPath: "terraform",
+				},
+			},
+		},
+	}
+
+	t.Setenv("DATABRICKS_HOST", "https://x")
+	t.Setenv("DATABRICKS_TOKEN", "foobar")
+	b.WorkspaceClient()
+
+	err = bundle.Apply(context.Background(), b, []bundle.Mutator{
+		Initialize(),
+		Load(),
+	})
+
+	require.ErrorContains(t, err, "Did you forget to run 'bricks bundle deploy'")
+}