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

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

pkg/config/common_test.go

@@ -129,6 +129,7 @@ func TestDefaultResource(t *testing.T) {
 		cmpopts.IgnoreFields(Resource{}, "useTerraformPluginSDKClient"),
 		cmpopts.IgnoreFields(Resource{}, "useTerraformPluginFrameworkClient"),
 		cmpopts.IgnoreFields(Resource{}, "requiredFields"),
+		cmpopts.IgnoreFields(Resource{}, "listConversionPaths"),
 	}
 
 	for name, tc := range cases {

pkg/config/provider.go

@@ -9,15 +9,14 @@ import (
 	"fmt"
 	"regexp"
 
-	"github.com/crossplane/upjet/pkg/schema/traverser"
-
 	tfjson "github.com/hashicorp/terraform-json"
 	fwprovider "github.com/hashicorp/terraform-plugin-framework/provider"
 	fwresource "github.com/hashicorp/terraform-plugin-framework/resource"
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
 	"github.com/pkg/errors"
 
 	"github.com/crossplane/upjet/pkg/registry"
+	"github.com/crossplane/upjet/pkg/schema/traverser"
 	conversiontfjson "github.com/crossplane/upjet/pkg/types/conversion/tfjson"
 )
 
@@ -157,6 +156,12 @@ 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 +264,32 @@ 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 +372,9 @@ 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 := traverseSchemas(name, terraformResource, p.Resources[name], p.schemaTraversers...); err != nil {
+			panic(errors.Wrap(err, "failed to execute the Terraform schema traverser chain"))
 		}
 	}
 	for i, refInjector := range p.refInjectors {
@@ -441,21 +457,3 @@ func terraformPluginFrameworkResourceFunctionsMap(provider fwprovider.Provider)
 
 	return resourceFunctionsMap
 }
-
-type listEmbedder struct {
-	traverser.NoopTraverser
-	r *Resource
-}
-
-func (l listEmbedder) VisitResource(r *traverser.ResourceNode) error {
-	// this visitor only works on sets and lists with the MaxItems constraint
-	// of 1.
-	if r.Schema.Type != schema.TypeList && r.Schema.Type != schema.TypeSet {
-		return nil
-	}
-	if r.Schema.MaxItems != 1 {
-		return nil
-	}
-	l.r.AddSingletonListConversion(traverser.FieldPathWithWildcard(r.TFPath))
-	return nil
-}

pkg/config/resource.go

@@ -554,10 +554,8 @@ func (m SchemaElementOptions) AddToObservation(el string) bool {
 // ListConversionPaths returns the Resource's runtime Terraform list
 // conversion paths in fieldpath syntax.
 func (r *Resource) ListConversionPaths() []string {
-	l := make([]string, 0, len(r.listConversionPaths))
-	for _, v := range r.listConversionPaths {
-		l = append(l, v)
-	}
+	var l []string
+	copy(l, r.listConversionPaths)
 	return l
 }
 

pkg/config/schema_conversions.go

@@ -0,0 +1,57 @@
+// SPDX-FileCopyrightText: 2024 The Crossplane Authors <https://crossplane.io>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package config
+
+import (
+	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
+
+	"github.com/crossplane/upjet/pkg/schema/traverser"
+)
+
+var _ ResourceSetter = &SingletonListEmbedder{}
+
+// ResourceSetter allows the context Resource to be set for a traverser.
+type ResourceSetter interface {
+	SetResource(r *Resource)
+}
+
+func traverseSchemas(tfName string, tfResource *schema.Resource, r *Resource, visitors ...traverser.SchemaTraverser) error {
+	// set the upjet Resource configuration as context for the visitors that
+	// satisfy the ResourceSetter interface.
+	for _, v := range visitors {
+		if rs, ok := v.(ResourceSetter); ok {
+			rs.SetResource(r)
+		}
+	}
+	return traverser.Traverse(tfName, tfResource, visitors...)
+}
+
+type resourceContext struct {
+	r *Resource
+}
+
+func (rc *resourceContext) SetResource(r *Resource) {
+	rc.r = r
+}
+
+// SingletonListEmbedder is a schema traverser for embedding singleton lists
+// in the Terraform schema as objects.
+type SingletonListEmbedder struct {
+	resourceContext
+	traverser.NoopTraverser
+}
+
+func (l *SingletonListEmbedder) VisitResource(r *traverser.ResourceNode) error {
+	// this visitor only works on sets and lists with the MaxItems constraint
+	// of 1.
+	if r.Schema.Type != schema.TypeList && r.Schema.Type != schema.TypeSet {
+		return nil
+	}
+	if r.Schema.MaxItems != 1 {
+		return nil
+	}
+	l.r.AddSingletonListConversion(traverser.FieldPathWithWildcard(r.TFPath))
+	return nil
+}

pkg/controller/conversion.go

@@ -64,7 +64,7 @@ func setValue(pv *fieldpath.Paved, v any, fp string) error {
 // an embedded object will be converted into a singleton list or a singleton
 // list will be converted into an embedded object) is determined by the mode
 // parameter.
-func convert(params map[string]any, paths []string, mode conversionMode) (map[string]any, error) {
+func convert(params map[string]any, paths []string, mode conversionMode) (map[string]any, error) { //nolint:gocyclo // easier to follow as a unit
 	switch mode {
 	case toSingletonList:
 		slices.Sort(paths)

pkg/controller/external_tfpluginsdk.go

@@ -581,7 +581,7 @@ func (n *terraformPluginSDKExternal) setExternalName(mg xpresource.Managed, stat
 	return oldName != newName, nil
 }
 
-func (n *terraformPluginSDKExternal) Create(ctx context.Context, mg xpresource.Managed) (managed.ExternalCreation, error) {
+func (n *terraformPluginSDKExternal) Create(ctx context.Context, mg xpresource.Managed) (managed.ExternalCreation, error) { //nolint:gocyclo // easier to follow as a unit
 	n.logger.Debug("Creating the external resource")
 	start := time.Now()
 	newState, diag := n.resourceSchema.Apply(ctx, n.opTracker.GetTfState(), n.instanceDiff, n.ts.Meta)

pkg/schema/traverser/traverse.go

@@ -19,12 +19,16 @@ const (
 var _ Element = &SchemaNode{}
 var _ Element = &ResourceNode{}
 
-// Traverse traverses the Terraform schema of the given Terraform resource and
-// visits each of the specified visitors on the traversed schema's nodes.
+// Traverse traverses the Terraform schema of the given Terraform resource
+// with the given Terraform resource name and visits each of the specified
+// visitors on the traversed schema's nodes.
 // If any of the visitors in the chain reports an error,
 // it stops the traversal.
-func Traverse(tfResource *schema.Resource, visitors ...SchemaTraverser) error {
-	return traverse(tfResource, Node{}, visitors...)
+func Traverse(tfName string, tfResource *schema.Resource, visitors ...SchemaTraverser) error {
+	if len(visitors) == 0 {
+		return nil
+	}
+	return traverse(tfResource, Node{TFName: tfName}, visitors...)
 }
 
 // SchemaTraverser represents a visitor on the schema.Schema and
@@ -44,6 +48,8 @@ type Element interface {
 
 // Node represents a schema node that's being traversed.
 type Node struct {
+	// TFName is the Terraform resource name
+	TFName string
 	// Schema is the Terraform schema associated with the visited node during a
 	// traversal.
 	Schema *schema.Schema
@@ -77,18 +83,18 @@ func (r *ResourceNode) Accept(v SchemaTraverser) error {
 	return v.VisitResource(r)
 }
 
-func traverse(tfResource *schema.Resource, pNode Node, visitors ...SchemaTraverser) error {
+func traverse(tfResource *schema.Resource, pNode Node, visitors ...SchemaTraverser) error { //nolint:gocyclo // traverse logic is easier to follow in a unit
 	m := tfResource.Schema
 	if m == nil && tfResource.SchemaFunc != nil {
 		m = tfResource.SchemaFunc()
 	}
 	if m == nil {
 		return nil
 	}
-	var node Node
+	node := Node{TFName: pNode.TFName}
 	for k, s := range m {
-		node.CRDPath = append(pNode.CRDPath, name.NewFromSnake(k).LowerCamelComputed)
-		node.TFPath = append(pNode.TFPath, k)
+		node.CRDPath = append(pNode.CRDPath, name.NewFromSnake(k).LowerCamelComputed) //nolint:gocritic // the parent node's path must not be modified
+		node.TFPath = append(pNode.TFPath, k)                                         //nolint:gocritic // the parent node's path must not be modified
 		node.Schema = s
 		switch e := s.Elem.(type) {
 		case *schema.Schema:

pkg/types/builder.go

@@ -11,14 +11,13 @@ import (
 	"sort"
 	"strings"
 
-	"github.com/crossplane/upjet/pkg/schema/traverser"
-
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
 	twtypes "github.com/muvaf/typewriter/pkg/types"
 	"github.com/pkg/errors"
 	"k8s.io/utils/ptr"
 
 	"github.com/crossplane/upjet/pkg/config"
+	"github.com/crossplane/upjet/pkg/schema/traverser"
 )
 
 const (

pkg/types/field.go

@@ -12,14 +12,13 @@ import (
 	"sort"
 	"strings"
 
-	"github.com/crossplane/upjet/pkg/schema/traverser"
-
 	"github.com/hashicorp/terraform-plugin-sdk/v2/helper/schema"
 	"github.com/pkg/errors"
 	"k8s.io/utils/ptr"
 
 	"github.com/crossplane/upjet/pkg"
 	"github.com/crossplane/upjet/pkg/config"
+	"github.com/crossplane/upjet/pkg/schema/traverser"
 	"github.com/crossplane/upjet/pkg/types/comments"
 	"github.com/crossplane/upjet/pkg/types/name"
 )