Fix panic when bundle auth resolution fails (#1002)

## Changes
CLI would panic if an invalid bundle auth is setup when running CLI
commands. This PR removes the panic and shows the error message directly
instead.

## Tests
The CWD is a bundle with:
```
workspace:
  profile: DEFAULT
```

Before:
```
shreyas.goenka@THW32HFW6T bundle-playground % cli clusters list
panic: resolve: /Users/shreyas.goenka/.databrickscfg has no DEFAULT profile configured. Config: profile=DEFAULT

goroutine 1 [running]:
```

After:
```
shreyas.goenka@THW32HFW6T bundle-playground % cli clusters list
Error: cannot resolve bundle auth configuration: resolve: /Users/shreyas.goenka/.databrickscfg has no DEFAULT profile configured. Config: profile=DEFAULT
```

```
shreyas.goenka@THW32HFW6T bundle-playground % DATABRICKS_CONFIG_FILE=/dev/null cli bundle deploy
Error:  cannot resolve bundle auth configuration: resolve: /dev/null has no DEFAULT profile configured. Config: profile=DEFAULT, config_file=/dev/null. Env: DATABRICKS_CONFIG_FILE
```

bundle/bundle.go

@@ -121,10 +121,18 @@ func TryLoad(ctx context.Context) (*Bundle, error) {
 	return Load(ctx, root)
 }
 
+func (b *Bundle) InitializeWorkspaceClient() (*databricks.WorkspaceClient, error) {
+	client, err := b.Config.Workspace.Client()
+	if err != nil {
+		return nil, fmt.Errorf("cannot resolve bundle auth configuration: %w", err)
+	}
+	return client, nil
+}
+
 func (b *Bundle) WorkspaceClient() *databricks.WorkspaceClient {
 	b.clientOnce.Do(func() {
 		var err error
-		b.client, err = b.Config.Workspace.Client()
+		b.client, err = b.InitializeWorkspaceClient()
 		if err != nil {
 			panic(err)
 		}

bundle/config/mutator/initialize_workspace_client.go

@@ -0,0 +1,25 @@
+package mutator
+
+import (
+	"context"
+
+	"github.com/databricks/cli/bundle"
+)
+
+type initializeWorkspaceClient struct{}
+
+func InitializeWorkspaceClient() bundle.Mutator {
+	return &initializeWorkspaceClient{}
+}
+
+func (m *initializeWorkspaceClient) Name() string {
+	return "InitializeWorkspaceClient"
+}
+
+// Apply initializes the workspace client for the bundle. We do this here so
+// downstream calls to b.WorkspaceClient() do not panic if there's an error in the
+// auth configuration.
+func (m *initializeWorkspaceClient) Apply(_ context.Context, b *bundle.Bundle) error {
+	_, err := b.InitializeWorkspaceClient()
+	return err
+}

bundle/phases/initialize.go

@@ -19,6 +19,7 @@ func Initialize() bundle.Mutator {
 	return newPhase(
 		"initialize",
 		[]bundle.Mutator{
+			mutator.InitializeWorkspaceClient(),
 			mutator.PopulateCurrentUser(),
 			mutator.SetRunAs(),
 			mutator.DefineDefaultWorkspaceRoot(),

cmd/root/auth.go

@@ -152,7 +152,11 @@ func MustWorkspaceClient(cmd *cobra.Command, args []string) error {
 			return err
 		}
 		if b := bundle.GetOrNil(cmd.Context()); b != nil {
-			cfg = b.WorkspaceClient().Config
+			client, err := b.InitializeWorkspaceClient()
+			if err != nil {
+				return err
+			}
+			cfg = client.Config
 		}
 	}
 

cmd/root/bundle_test.go

@@ -95,7 +95,7 @@ func TestBundleConfigureWithMismatchedProfile(t *testing.T) {
 	cmd.Flag("profile").Value.Set("PROFILE-1")
 
 	b := setup(t, cmd, "https://x.com")
-	assert.PanicsWithError(t, "config host mismatch: profile uses host https://a.com, but CLI configured to use https://x.com", func() {
+	assert.PanicsWithError(t, "cannot resolve bundle auth configuration: config host mismatch: profile uses host https://a.com, but CLI configured to use https://x.com", func() {
 		b.WorkspaceClient()
 	})
 }
@@ -118,7 +118,7 @@ func TestBundleConfigureWithMismatchedProfileEnvVariable(t *testing.T) {
 
 	cmd := emptyCommand(t)
 	b := setup(t, cmd, "https://x.com")
-	assert.PanicsWithError(t, "config host mismatch: profile uses host https://a.com, but CLI configured to use https://x.com", func() {
+	assert.PanicsWithError(t, "cannot resolve bundle auth configuration: config host mismatch: profile uses host https://a.com, but CLI configured to use https://x.com", func() {
 		b.WorkspaceClient()
 	})
 }