Make singleton-list-to-embedded-object API conversion optional

Signed-off-by: Alper Rifat Ulucinar <ulucinar@users.noreply.github.com>

Author: ulucinar

pkg/config/provider.go

@@ -157,6 +157,12 @@ type Provider struct {
 	// resourceConfigurators is a map holding resource configurators where key
 	// is Terraform resource name.
 	resourceConfigurators map[string]ResourceConfiguratorChain
+
+	// schemaTraversers is a chain of schema traversers to be used with
+	// this Provider configuration. Schema traversers can be used to inspect or
+	// modify the Provider configuration based on the underlying Terraform
+	// resource schemas.
+	schemaTraversers []traverser.SchemaTraverser
 }
 
 // ReferenceInjector injects cross-resource references across the resources
@@ -259,19 +265,32 @@ func WithFeaturesPackage(s string) ProviderOption {
 	}
 }
 
+// WithMainTemplate configures the provider family main module file's path.
+// This template file will be used to generate the main modules of the
+// family's members.
 func WithMainTemplate(template string) ProviderOption {
 	return func(p *Provider) {
 		p.MainTemplate = template
 	}
 }
 
+// WithSchemaTraversers configures a chain of schema traversers to be used with
+// this Provider configuration. Schema traversers can be used to inspect or
+// modify the Provider configuration based on the underlying Terraform
+// resource schemas.
+func WithSchemaTraversers(traversers ...traverser.SchemaTraverser) ProviderOption {
+	return func(p *Provider) {
+		p.schemaTraversers = traversers
+	}
+}
+
 // NewProvider builds and returns a new Provider from provider
 // tfjson schema, that is generated using Terraform CLI with:
 // `terraform providers schema --json`
 func NewProvider(schema []byte, prefix string, modulePath string, metadata []byte, opts ...ProviderOption) *Provider { //nolint:gocyclo
 	ps := tfjson.ProviderSchemas{}
 	if err := ps.UnmarshalJSON(schema); err != nil {
-		panic(err)
+		panic(errors.Wrap(err, "failed to unmarshal the Terraform JSON schema"))
 	}
 	if len(ps.Schemas) != 1 {
 		panic(fmt.Sprintf("there should exactly be 1 provider schema but there are %d", len(ps.Schemas)))
@@ -354,11 +373,9 @@ func NewProvider(schema []byte, prefix string, modulePath string, metadata []byt
 		p.Resources[name].useTerraformPluginSDKClient = isTerraformPluginSDK
 		p.Resources[name].useTerraformPluginFrameworkClient = isPluginFrameworkResource
 		// traverse the Terraform resource schema to initialize the upjet Resource
-		// configuration using:
-		// - listEmbedder: This traverser marks lists of length at most 1
-		// (singleton lists) as embedded objects.
-		if err := traverser.Traverse(terraformResource, listEmbedder{r: p.Resources[name]}); err != nil {
-			panic(err)
+		// configurations
+		if err := traverser.Traverse(terraformResource, p.schemaTraversers...); err != nil {
+			panic(errors.Wrap(err, "failed to execute the Terraform schema traverser chain"))
 		}
 	}
 	for i, refInjector := range p.refInjectors {

pkg/schema/traverser/traverse.go

@@ -24,6 +24,9 @@ var _ Element = &ResourceNode{}
 // If any of the visitors in the chain reports an error,
 // it stops the traversal.
 func Traverse(tfResource *schema.Resource, visitors ...SchemaTraverser) error {
+	if len(visitors) == 0 {
+		return nil
+	}
 	return traverse(tfResource, Node{}, visitors...)
 }