feat(sdlmerge): add shared types for GraphQL schema handling

Introduce types for managing fielded, enum, union, and scalar shared types.
Implement functionality for comparing values and creating field sets.
Enhance schema extensions by integrating new visitors for enum types.

sdlmerge/collect_entities.go

@@ -0,0 +1,61 @@
+package sdlmerge
+
+import (
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/ast"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/astvisitor"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/operationreport"
+)
+
+type collectEntitiesVisitor struct {
+	*astvisitor.Walker
+	document          *ast.Document
+	collectedEntities entitySet
+}
+
+func newCollectEntitiesVisitor(collectedEntities entitySet) *collectEntitiesVisitor {
+	return &collectEntitiesVisitor{
+		collectedEntities: collectedEntities,
+	}
+}
+
+func (c *collectEntitiesVisitor) Register(walker *astvisitor.Walker) {
+	c.Walker = walker
+	walker.RegisterEnterDocumentVisitor(c)
+	walker.RegisterEnterInterfaceTypeDefinitionVisitor(c)
+	walker.RegisterEnterObjectTypeDefinitionVisitor(c)
+}
+
+func (c *collectEntitiesVisitor) EnterDocument(operation, _ *ast.Document) {
+	c.document = operation
+}
+
+func (c *collectEntitiesVisitor) EnterInterfaceTypeDefinition(ref int) {
+	interfaceType := c.document.InterfaceTypeDefinitions[ref]
+	name := c.document.InterfaceTypeDefinitionNameString(ref)
+	if err := c.resolvePotentialEntity(name, interfaceType.Directives.Refs); err != nil {
+		c.StopWithExternalErr(*err)
+	}
+}
+
+func (c *collectEntitiesVisitor) EnterObjectTypeDefinition(ref int) {
+	objectType := c.document.ObjectTypeDefinitions[ref]
+	name := c.document.ObjectTypeDefinitionNameString(ref)
+	if err := c.resolvePotentialEntity(name, objectType.Directives.Refs); err != nil {
+		c.StopWithExternalErr(*err)
+	}
+}
+
+func (c *collectEntitiesVisitor) resolvePotentialEntity(name string, directiveRefs []int) *operationreport.ExternalError {
+	if _, exists := c.collectedEntities[name]; exists {
+		err := operationreport.ErrEntitiesMustNotBeDuplicated(name)
+		return &err
+	}
+	for _, directiveRef := range directiveRefs {
+		if c.document.DirectiveNameString(directiveRef) != "key" {
+			continue
+		}
+		c.collectedEntities[name] = struct{}{}
+		return nil
+	}
+	return nil
+}

sdlmerge/enum_type_extending.go

@@ -0,0 +1,50 @@
+package sdlmerge
+
+import (
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/ast"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/astvisitor"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/operationreport"
+)
+
+type extendEnumTypeDefinitionVisitor struct {
+	*astvisitor.Walker
+	document *ast.Document
+}
+
+func newExtendEnumTypeDefinition() *extendEnumTypeDefinitionVisitor {
+	return &extendEnumTypeDefinitionVisitor{}
+}
+
+func (e *extendEnumTypeDefinitionVisitor) Register(walker *astvisitor.Walker) {
+	e.Walker = walker
+	walker.RegisterEnterDocumentVisitor(e)
+	walker.RegisterEnterEnumTypeExtensionVisitor(e)
+}
+
+func (e *extendEnumTypeDefinitionVisitor) EnterDocument(operation, _ *ast.Document) {
+	e.document = operation
+}
+
+func (e *extendEnumTypeDefinitionVisitor) EnterEnumTypeExtension(ref int) {
+	nodes, exists := e.document.Index.NodesByNameBytes(e.document.EnumTypeExtensionNameBytes(ref))
+	if !exists {
+		return
+	}
+
+	hasExtended := false
+	for i := range nodes {
+		if nodes[i].Kind != ast.NodeKindEnumTypeDefinition {
+			continue
+		}
+		if hasExtended {
+			e.StopWithExternalErr(operationreport.ErrSharedTypesMustNotBeExtended(e.document.EnumTypeExtensionNameString(ref)))
+			return
+		}
+		e.document.ExtendEnumTypeDefinitionByEnumTypeExtension(nodes[i].Ref, ref)
+		hasExtended = true
+	}
+
+	if !hasExtended {
+		e.StopWithExternalErr(operationreport.ErrExtensionOrphansMustResolveInSupergraph(e.document.EnumTypeExtensionNameBytes(ref)))
+	}
+}

sdlmerge/input_type_extending.go

@@ -0,0 +1,50 @@
+package sdlmerge
+
+import (
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/ast"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/astvisitor"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/operationreport"
+)
+
+func newExtendInputObjectTypeDefinition() *extendInputObjectTypeDefinitionVisitor {
+	return &extendInputObjectTypeDefinitionVisitor{}
+}
+
+type extendInputObjectTypeDefinitionVisitor struct {
+	*astvisitor.Walker
+	document *ast.Document
+}
+
+func (e *extendInputObjectTypeDefinitionVisitor) Register(walker *astvisitor.Walker) {
+	e.Walker = walker
+	walker.RegisterEnterDocumentVisitor(e)
+	walker.RegisterEnterInputObjectTypeExtensionVisitor(e)
+}
+
+func (e *extendInputObjectTypeDefinitionVisitor) EnterDocument(operation, _ *ast.Document) {
+	e.document = operation
+}
+
+func (e *extendInputObjectTypeDefinitionVisitor) EnterInputObjectTypeExtension(ref int) {
+	nodes, exists := e.document.Index.NodesByNameBytes(e.document.InputObjectTypeExtensionNameBytes(ref))
+	if !exists {
+		return
+	}
+
+	hasExtended := false
+	for i := range nodes {
+		if nodes[i].Kind != ast.NodeKindInputObjectTypeDefinition {
+			continue
+		}
+		if hasExtended {
+			e.StopWithExternalErr(operationreport.ErrSharedTypesMustNotBeExtended(e.document.InputObjectTypeExtensionNameString(ref)))
+			return
+		}
+		e.document.ExtendInputObjectTypeDefinitionByInputObjectTypeExtension(nodes[i].Ref, ref)
+		hasExtended = true
+	}
+
+	if !hasExtended {
+		e.StopWithExternalErr(operationreport.ErrExtensionOrphansMustResolveInSupergraph(e.document.InputObjectTypeExtensionNameBytes(ref)))
+	}
+}

sdlmerge/interface_type_extending.go

@@ -0,0 +1,63 @@
+package sdlmerge
+
+import (
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/ast"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/astvisitor"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/operationreport"
+)
+
+func newExtendInterfaceTypeDefinition(collectedEntities entitySet) *extendInterfaceTypeDefinitionVisitor {
+	return &extendInterfaceTypeDefinitionVisitor{
+		collectedEntities: collectedEntities,
+	}
+}
+
+type extendInterfaceTypeDefinitionVisitor struct {
+	*astvisitor.Walker
+	document          *ast.Document
+	collectedEntities entitySet
+}
+
+func (e *extendInterfaceTypeDefinitionVisitor) Register(walker *astvisitor.Walker) {
+	e.Walker = walker
+	walker.RegisterEnterDocumentVisitor(e)
+	walker.RegisterEnterInterfaceTypeExtensionVisitor(e)
+}
+
+func (e *extendInterfaceTypeDefinitionVisitor) EnterDocument(operation, _ *ast.Document) {
+	e.document = operation
+}
+
+func (e *extendInterfaceTypeDefinitionVisitor) EnterInterfaceTypeExtension(ref int) {
+	nameBytes := e.document.InterfaceTypeExtensionNameBytes(ref)
+	nodes, exists := e.document.Index.NodesByNameBytes(nameBytes)
+	if !exists {
+		return
+	}
+
+	var nodeToExtend *ast.Node
+	isEntity := false
+	for i := range nodes {
+		if nodes[i].Kind != ast.NodeKindInterfaceTypeDefinition {
+			continue
+		}
+		if nodeToExtend != nil {
+			e.StopWithExternalErr(*multipleExtensionError(isEntity, nameBytes))
+			return
+		}
+		var err *operationreport.ExternalError
+		extension := e.document.InterfaceTypeExtensions[ref]
+		if isEntity, err = e.collectedEntities.isExtensionForEntity(nameBytes, extension.Directives.Refs, e.document); err != nil {
+			e.StopWithExternalErr(*err)
+			return
+		}
+		nodeToExtend = &nodes[i]
+	}
+
+	if nodeToExtend == nil {
+		e.StopWithExternalErr(operationreport.ErrExtensionOrphansMustResolveInSupergraph(e.document.InterfaceTypeExtensionNameBytes(ref)))
+		return
+	}
+
+	e.document.ExtendInterfaceTypeDefinitionByInterfaceTypeExtension(nodeToExtend.Ref, ref)
+}

sdlmerge/merge_duplicated_fields.go

@@ -0,0 +1,62 @@
+package sdlmerge
+
+import (
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/ast"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/astvisitor"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/operationreport"
+)
+
+type mergeDuplicatedFieldsVisitor struct {
+	*astvisitor.Walker
+	document *ast.Document
+}
+
+func newMergeDuplicatedFieldsVisitor() *mergeDuplicatedFieldsVisitor {
+	return &mergeDuplicatedFieldsVisitor{
+		nil,
+		nil,
+	}
+}
+
+func (m *mergeDuplicatedFieldsVisitor) Register(walker *astvisitor.Walker) {
+	m.Walker = walker
+	walker.RegisterEnterDocumentVisitor(m)
+	walker.RegisterLeaveObjectTypeDefinitionVisitor(m)
+}
+
+func (m *mergeDuplicatedFieldsVisitor) EnterDocument(document, _ *ast.Document) {
+	m.document = document
+}
+
+func (m *mergeDuplicatedFieldsVisitor) LeaveObjectTypeDefinition(ref int) {
+	var refsForDeletion []int
+	fieldByTypeRefSet := make(map[string]int)
+	for _, fieldRef := range m.document.ObjectTypeDefinitions[ref].FieldsDefinition.Refs {
+		fieldName := m.document.FieldDefinitionNameString(fieldRef)
+		newTypeRef := m.document.FieldDefinitions[fieldRef].Type
+		if oldTypeRef, ok := fieldByTypeRefSet[fieldName]; ok {
+			if m.document.TypesAreEqualDeep(oldTypeRef, newTypeRef) {
+				refsForDeletion = append(refsForDeletion, fieldRef)
+				continue
+			}
+			oldFieldTypeNameBytes, err := m.document.PrintTypeBytes(oldTypeRef, nil)
+			if err != nil {
+				m.Walker.StopWithInternalErr(err)
+				return
+			}
+			newFieldTypeNameBytes, err := m.document.PrintTypeBytes(newTypeRef, nil)
+			if err != nil {
+				m.Walker.StopWithInternalErr(err)
+				return
+			}
+			m.Walker.StopWithExternalErr(operationreport.ErrDuplicateFieldsMustBeIdentical(
+				fieldName, m.document.ObjectTypeDefinitionNameString(ref), string(oldFieldTypeNameBytes), string(newFieldTypeNameBytes),
+			))
+			return
+		}
+
+		fieldByTypeRefSet[fieldName] = newTypeRef
+	}
+
+	m.document.RemoveFieldDefinitionsFromObjectTypeDefinition(refsForDeletion, ref)
+}

sdlmerge/object_type_extending.go

@@ -0,0 +1,66 @@
+package sdlmerge
+
+import (
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/ast"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/astvisitor"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/operationreport"
+)
+
+func newExtendObjectTypeDefinition(collectedEntities entitySet) *extendObjectTypeDefinitionVisitor {
+	return &extendObjectTypeDefinitionVisitor{
+		collectedEntities: collectedEntities,
+	}
+}
+
+type extendObjectTypeDefinitionVisitor struct {
+	*astvisitor.Walker
+	document          *ast.Document
+	collectedEntities entitySet
+}
+
+func (e *extendObjectTypeDefinitionVisitor) Register(walker *astvisitor.Walker) {
+	e.Walker = walker
+	walker.RegisterEnterDocumentVisitor(e)
+	walker.RegisterEnterObjectTypeExtensionVisitor(e)
+}
+
+func (e *extendObjectTypeDefinitionVisitor) EnterDocument(operation, _ *ast.Document) {
+	e.document = operation
+}
+
+func (e *extendObjectTypeDefinitionVisitor) EnterObjectTypeExtension(ref int) {
+	nameBytes := e.document.ObjectTypeExtensionNameBytes(ref)
+	nodes, exists := e.document.Index.NodesByNameBytes(nameBytes)
+	if !exists {
+		return
+	}
+
+	var nodeToExtend *ast.Node
+	isEntity := false
+	for i := range nodes {
+		if nodes[i].Kind != ast.NodeKindObjectTypeDefinition {
+			continue
+		}
+		if nodeToExtend != nil {
+			e.StopWithExternalErr(*multipleExtensionError(isEntity, nameBytes))
+			return
+		}
+		var err *operationreport.ExternalError
+		extension := e.document.ObjectTypeExtensions[ref]
+		if isEntity, err = e.collectedEntities.isExtensionForEntity(nameBytes, extension.Directives.Refs, e.document); err != nil {
+			e.StopWithExternalErr(*err)
+			return
+		}
+		nodeToExtend = &nodes[i]
+		if ast.IsRootType(nameBytes) {
+			break
+		}
+	}
+
+	if nodeToExtend == nil {
+		e.StopWithExternalErr(operationreport.ErrExtensionOrphansMustResolveInSupergraph(nameBytes))
+		return
+	}
+
+	e.document.ExtendObjectTypeDefinitionByObjectTypeExtension(nodeToExtend.Ref, ref)
+}

sdlmerge/remove_duplicate_fielded_shared_types.go

@@ -0,0 +1,107 @@
+package sdlmerge
+
+import (
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/ast"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/astvisitor"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/operationreport"
+)
+
+type removeDuplicateFieldedSharedTypesVisitor struct {
+	*astvisitor.Walker
+	document          *ast.Document
+	sharedTypeSet     map[string]fieldedSharedType
+	rootNodesToRemove []ast.Node
+	lastInputRef      int
+	lastInterfaceRef  int
+	lastObjectRef     int
+}
+
+func newRemoveDuplicateFieldedSharedTypesVisitor() *removeDuplicateFieldedSharedTypesVisitor {
+	return &removeDuplicateFieldedSharedTypesVisitor{
+		nil,
+		nil,
+		make(map[string]fieldedSharedType),
+		nil,
+		ast.InvalidRef,
+		ast.InvalidRef,
+		ast.InvalidRef,
+	}
+}
+
+func (r *removeDuplicateFieldedSharedTypesVisitor) Register(walker *astvisitor.Walker) {
+	r.Walker = walker
+	walker.RegisterEnterDocumentVisitor(r)
+	walker.RegisterEnterInputObjectTypeDefinitionVisitor(r)
+	walker.RegisterEnterInterfaceTypeDefinitionVisitor(r)
+	walker.RegisterEnterObjectTypeDefinitionVisitor(r)
+	walker.RegisterLeaveDocumentVisitor(r)
+}
+
+func (r *removeDuplicateFieldedSharedTypesVisitor) EnterDocument(operation, _ *ast.Document) {
+	r.document = operation
+}
+
+func (r *removeDuplicateFieldedSharedTypesVisitor) EnterInputObjectTypeDefinition(ref int) {
+	if ref <= r.lastInputRef {
+		return
+	}
+	name := r.document.InputObjectTypeDefinitionNameString(ref)
+	refs := r.document.InputObjectTypeDefinitions[ref].InputFieldsDefinition.Refs
+	input, exists := r.sharedTypeSet[name]
+	if exists {
+		if !input.areFieldsIdentical(refs) {
+			r.StopWithExternalErr(operationreport.ErrSharedTypesMustBeIdenticalToFederate(name))
+			return
+		}
+		r.rootNodesToRemove = append(r.rootNodesToRemove, ast.Node{Kind: ast.NodeKindInputObjectTypeDefinition, Ref: ref})
+	} else {
+		r.sharedTypeSet[name] = newFieldedSharedType(r.document, ast.NodeKindInputValueDefinition, refs)
+	}
+	r.lastInputRef = ref
+}
+
+func (r *removeDuplicateFieldedSharedTypesVisitor) EnterInterfaceTypeDefinition(ref int) {
+	if ref <= r.lastInterfaceRef {
+		return
+	}
+	name := r.document.InterfaceTypeDefinitionNameString(ref)
+	interfaceType := r.document.InterfaceTypeDefinitions[ref]
+	refs := interfaceType.FieldsDefinition.Refs
+	iFace, exists := r.sharedTypeSet[name]
+	if exists {
+		if !iFace.areFieldsIdentical(refs) {
+			r.StopWithExternalErr(operationreport.ErrSharedTypesMustBeIdenticalToFederate(name))
+			return
+		}
+		r.rootNodesToRemove = append(r.rootNodesToRemove, ast.Node{Kind: ast.NodeKindInterfaceTypeDefinition, Ref: ref})
+	} else {
+		r.sharedTypeSet[name] = newFieldedSharedType(r.document, ast.NodeKindFieldDefinition, refs)
+	}
+	r.lastInterfaceRef = ref
+}
+
+func (r *removeDuplicateFieldedSharedTypesVisitor) EnterObjectTypeDefinition(ref int) {
+	if ref <= r.lastObjectRef {
+		return
+	}
+	name := r.document.ObjectTypeDefinitionNameString(ref)
+	objectType := r.document.ObjectTypeDefinitions[ref]
+	refs := objectType.FieldsDefinition.Refs
+	object, exists := r.sharedTypeSet[name]
+	if exists {
+		if !object.areFieldsIdentical(refs) {
+			r.StopWithExternalErr(operationreport.ErrSharedTypesMustBeIdenticalToFederate(name))
+			return
+		}
+		r.rootNodesToRemove = append(r.rootNodesToRemove, ast.Node{Kind: ast.NodeKindObjectTypeDefinition, Ref: ref})
+	} else {
+		r.sharedTypeSet[name] = newFieldedSharedType(r.document, ast.NodeKindFieldDefinition, refs)
+	}
+	r.lastObjectRef = ref
+}
+
+func (r *removeDuplicateFieldedSharedTypesVisitor) LeaveDocument(_, _ *ast.Document) {
+	if r.rootNodesToRemove != nil {
+		r.document.DeleteRootNodes(r.rootNodesToRemove)
+	}
+}

sdlmerge/remove_duplicate_fieldless_shared_types.go

@@ -0,0 +1,98 @@
+package sdlmerge
+
+import (
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/ast"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/astvisitor"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/operationreport"
+)
+
+type removeDuplicateFieldlessSharedTypesVisitor struct {
+	*astvisitor.Walker
+	document          *ast.Document
+	sharedTypeSet     map[string]fieldlessSharedType
+	rootNodesToRemove []ast.Node
+	lastEnumRef       int
+	lastUnionRef      int
+	lastScalarRef     int
+}
+
+func newRemoveDuplicateFieldlessSharedTypesVisitor() *removeDuplicateFieldlessSharedTypesVisitor {
+	return &removeDuplicateFieldlessSharedTypesVisitor{
+		nil,
+		nil,
+		make(map[string]fieldlessSharedType),
+		nil,
+		ast.InvalidRef,
+		ast.InvalidRef,
+		ast.InvalidRef,
+	}
+}
+
+func (r *removeDuplicateFieldlessSharedTypesVisitor) Register(walker *astvisitor.Walker) {
+	r.Walker = walker
+	walker.RegisterEnterDocumentVisitor(r)
+	walker.RegisterEnterEnumTypeDefinitionVisitor(r)
+	walker.RegisterEnterScalarTypeDefinitionVisitor(r)
+	walker.RegisterEnterUnionTypeDefinitionVisitor(r)
+	walker.RegisterLeaveDocumentVisitor(r)
+}
+
+func (r *removeDuplicateFieldlessSharedTypesVisitor) EnterDocument(operation, _ *ast.Document) {
+	r.document = operation
+}
+
+func (r *removeDuplicateFieldlessSharedTypesVisitor) EnterEnumTypeDefinition(ref int) {
+	if ref <= r.lastEnumRef {
+		return
+	}
+	name := r.document.EnumTypeDefinitionNameString(ref)
+	enum, exists := r.sharedTypeSet[name]
+	if exists {
+		if !enum.areValuesIdentical(r.document.EnumTypeDefinitions[ref].EnumValuesDefinition.Refs) {
+			r.StopWithExternalErr(operationreport.ErrSharedTypesMustBeIdenticalToFederate(name))
+			return
+		}
+		r.rootNodesToRemove = append(r.rootNodesToRemove, ast.Node{Kind: ast.NodeKindEnumTypeDefinition, Ref: ref})
+	} else {
+		r.sharedTypeSet[name] = newEnumSharedType(r.document, ref)
+	}
+	r.lastEnumRef = ref
+}
+
+func (r *removeDuplicateFieldlessSharedTypesVisitor) EnterScalarTypeDefinition(ref int) {
+	if ref <= r.lastScalarRef {
+		return
+	}
+	name := r.document.ScalarTypeDefinitionNameString(ref)
+	_, exists := r.sharedTypeSet[name]
+	if exists {
+		r.rootNodesToRemove = append(r.rootNodesToRemove, ast.Node{Kind: ast.NodeKindScalarTypeDefinition, Ref: ref})
+	} else {
+		r.sharedTypeSet[name] = scalarSharedType{}
+	}
+	r.lastScalarRef = ref
+}
+
+func (r *removeDuplicateFieldlessSharedTypesVisitor) EnterUnionTypeDefinition(ref int) {
+	if ref <= r.lastUnionRef {
+		return
+	}
+	name := r.document.UnionTypeDefinitionNameString(ref)
+	union, exists := r.sharedTypeSet[name]
+	if exists {
+		if !union.areValuesIdentical(r.document.UnionTypeDefinitions[ref].UnionMemberTypes.Refs) {
+			r.StopWithExternalErr(operationreport.ErrSharedTypesMustBeIdenticalToFederate(name))
+			return
+		}
+		r.rootNodesToRemove = append(r.rootNodesToRemove, ast.Node{Kind: ast.NodeKindUnionTypeDefinition, Ref: ref})
+	} else {
+		r.sharedTypeSet[name] = newUnionSharedType(r.document, ref)
+	}
+	r.lastUnionRef = ref
+}
+
+func (r *removeDuplicateFieldlessSharedTypesVisitor) LeaveDocument(_, _ *ast.Document) {
+	if r.rootNodesToRemove != nil {
+		r.document.DeleteRootNodes(r.rootNodesToRemove)
+	}
+}

sdlmerge/remove_empty_object_type_definition.go

@@ -0,0 +1,32 @@
+package sdlmerge
+
+import (
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/ast"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/astvisitor"
+)
+
+func newRemoveEmptyObjectTypeDefinition() *removeEmptyObjectTypeDefinition {
+	return &removeEmptyObjectTypeDefinition{}
+}
+
+type removeEmptyObjectTypeDefinition struct{}
+
+func (r *removeEmptyObjectTypeDefinition) Register(walker *astvisitor.Walker) {
+	walker.RegisterLeaveDocumentVisitor(r)
+}
+
+func (r *removeEmptyObjectTypeDefinition) LeaveDocument(operation, _ *ast.Document) {
+	for ref := range operation.ObjectTypeDefinitions {
+		if operation.ObjectTypeDefinitions[ref].HasFieldDefinitions {
+			continue
+		}
+
+		name := operation.ObjectTypeDefinitionNameString(ref)
+		node, ok := operation.Index.FirstNodeByNameStr(name)
+		if !ok {
+			return
+		}
+
+		operation.RemoveRootNode(node)
+	}
+}

sdlmerge/remove_field_definition_by_directive.go

@@ -0,0 +1,46 @@
+package sdlmerge
+
+import (
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/ast"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/astvisitor"
+)
+
+func newRemoveFieldDefinitions(directives ...string) *removeFieldDefinitionByDirective {
+	directivesSet := make(map[string]struct{}, len(directives))
+	for _, directive := range directives {
+		directivesSet[directive] = struct{}{}
+	}
+
+	return &removeFieldDefinitionByDirective{
+		directives: directivesSet,
+	}
+}
+
+type removeFieldDefinitionByDirective struct {
+	operation  *ast.Document
+	directives map[string]struct{}
+}
+
+func (r *removeFieldDefinitionByDirective) Register(walker *astvisitor.Walker) {
+	walker.RegisterEnterDocumentVisitor(r)
+	walker.RegisterLeaveObjectTypeDefinitionVisitor(r)
+}
+
+func (r *removeFieldDefinitionByDirective) EnterDocument(operation, _ *ast.Document) {
+	r.operation = operation
+}
+
+func (r *removeFieldDefinitionByDirective) LeaveObjectTypeDefinition(ref int) {
+	var refsForDeletion []int
+	// select fields for deletion
+	for _, fieldRef := range r.operation.ObjectTypeDefinitions[ref].FieldsDefinition.Refs {
+		for _, directiveRef := range r.operation.FieldDefinitions[fieldRef].Directives.Refs {
+			directiveName := r.operation.DirectiveNameString(directiveRef)
+			if _, ok := r.directives[directiveName]; ok {
+				refsForDeletion = append(refsForDeletion, fieldRef)
+			}
+		}
+	}
+	// delete fields
+	r.operation.RemoveFieldDefinitionsFromObjectTypeDefinition(refsForDeletion, ref)
+}

sdlmerge/remove_field_definition_directive.go

@@ -0,0 +1,44 @@
+package sdlmerge
+
+import (
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/ast"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/astvisitor"
+)
+
+func newRemoveFieldDefinitionDirective(directives ...string) *removeFieldDefinitionDirective {
+	directivesSet := make(map[string]struct{}, len(directives))
+	for _, directive := range directives {
+		directivesSet[directive] = struct{}{}
+	}
+
+	return &removeFieldDefinitionDirective{
+		directives: directivesSet,
+	}
+}
+
+type removeFieldDefinitionDirective struct {
+	operation  *ast.Document
+	directives map[string]struct{}
+}
+
+func (r *removeFieldDefinitionDirective) Register(walker *astvisitor.Walker) {
+	walker.RegisterEnterDocumentVisitor(r)
+	walker.RegisterEnterFieldDefinitionVisitor(r)
+}
+
+func (r *removeFieldDefinitionDirective) EnterDocument(operation, _ *ast.Document) {
+	r.operation = operation
+}
+
+func (r *removeFieldDefinitionDirective) EnterFieldDefinition(ref int) {
+	var refsForDeletion []int
+	// select directives for deletion
+	for _, directiveRef := range r.operation.FieldDefinitions[ref].Directives.Refs {
+		directiveName := r.operation.DirectiveNameString(directiveRef)
+		if _, ok := r.directives[directiveName]; ok {
+			refsForDeletion = append(refsForDeletion, directiveRef)
+		}
+	}
+	// delete directives
+	r.operation.RemoveDirectivesFromNode(ast.Node{Kind: ast.NodeKindFieldDefinition, Ref: ref}, refsForDeletion)
+}

sdlmerge/remove_interface_definition_directive.go

@@ -0,0 +1,45 @@
+package sdlmerge
+
+import (
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/ast"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/astvisitor"
+)
+
+func newRemoveInterfaceDefinitionDirective(directives ...string) *removeInterfaceDefinitionDirective {
+	directivesSet := make(map[string]struct{}, len(directives))
+	for _, directive := range directives {
+		directivesSet[directive] = struct{}{}
+	}
+
+	return &removeInterfaceDefinitionDirective{
+		directives: directivesSet,
+	}
+}
+
+type removeInterfaceDefinitionDirective struct {
+	*astvisitor.Walker
+	operation  *ast.Document
+	directives map[string]struct{}
+}
+
+func (r *removeInterfaceDefinitionDirective) Register(walker *astvisitor.Walker) {
+	walker.RegisterEnterDocumentVisitor(r)
+	walker.RegisterEnterInterfaceTypeDefinitionVisitor(r)
+}
+
+func (r *removeInterfaceDefinitionDirective) EnterDocument(operation, _ *ast.Document) {
+	r.operation = operation
+}
+
+func (r *removeInterfaceDefinitionDirective) EnterInterfaceTypeDefinition(ref int) {
+	var refsForDeletion []int
+	// select fields for deletion
+	for _, directiveRef := range r.operation.InterfaceTypeDefinitions[ref].Directives.Refs {
+		directiveName := r.operation.DirectiveNameString(directiveRef)
+		if _, ok := r.directives[directiveName]; ok {
+			refsForDeletion = append(refsForDeletion, directiveRef)
+		}
+	}
+	// delete directives
+	r.operation.RemoveDirectivesFromNode(ast.Node{Kind: ast.NodeKindInterfaceTypeDefinition, Ref: ref}, refsForDeletion)
+}

sdlmerge/remove_object_type_definition_directive.go

@@ -0,0 +1,44 @@
+package sdlmerge
+
+import (
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/ast"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/astvisitor"
+)
+
+func newRemoveObjectTypeDefinitionDirective(directives ...string) *removeObjectTypeDefinitionDirective {
+	directivesSet := make(map[string]struct{}, len(directives))
+	for _, directive := range directives {
+		directivesSet[directive] = struct{}{}
+	}
+
+	return &removeObjectTypeDefinitionDirective{
+		directives: directivesSet,
+	}
+}
+
+type removeObjectTypeDefinitionDirective struct {
+	operation  *ast.Document
+	directives map[string]struct{}
+}
+
+func (r *removeObjectTypeDefinitionDirective) Register(walker *astvisitor.Walker) {
+	walker.RegisterEnterDocumentVisitor(r)
+	walker.RegisterEnterObjectTypeDefinitionVisitor(r)
+}
+
+func (r *removeObjectTypeDefinitionDirective) EnterDocument(operation, _ *ast.Document) {
+	r.operation = operation
+}
+
+func (r *removeObjectTypeDefinitionDirective) EnterObjectTypeDefinition(ref int) {
+	var refsForDeletion []int
+	// select fields for deletion
+	for _, directiveRef := range r.operation.ObjectTypeDefinitions[ref].Directives.Refs {
+		directiveName := r.operation.DirectiveNameString(directiveRef)
+		if _, ok := r.directives[directiveName]; ok {
+			refsForDeletion = append(refsForDeletion, directiveRef)
+		}
+	}
+	// delete directives
+	r.operation.RemoveDirectivesFromNode(ast.Node{Kind: ast.NodeKindObjectTypeDefinition, Ref: ref}, refsForDeletion)
+}

sdlmerge/remove_type_extensions.go

@@ -0,0 +1,20 @@
+package sdlmerge
+
+import (
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/ast"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/astvisitor"
+)
+
+func newRemoveMergedTypeExtensions() *removeMergedTypeExtensionsVisitor {
+	return &removeMergedTypeExtensionsVisitor{}
+}
+
+type removeMergedTypeExtensionsVisitor struct{}
+
+func (r *removeMergedTypeExtensionsVisitor) Register(walker *astvisitor.Walker) {
+	walker.RegisterLeaveDocumentVisitor(r)
+}
+
+func (r *removeMergedTypeExtensionsVisitor) LeaveDocument(operation, definition *ast.Document) {
+	operation.RemoveMergedTypeExtensions()
+}

sdlmerge/scalar_type_extending.go

@@ -0,0 +1,49 @@
+package sdlmerge
+
+import (
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/ast"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/astvisitor"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/operationreport"
+)
+
+func newExtendScalarTypeDefinition() *extendScalarTypeDefinitionVisitor {
+	return &extendScalarTypeDefinitionVisitor{}
+}
+
+type extendScalarTypeDefinitionVisitor struct {
+	*astvisitor.Walker
+	document *ast.Document
+}
+
+func (e *extendScalarTypeDefinitionVisitor) Register(walker *astvisitor.Walker) {
+	e.Walker = walker
+	walker.RegisterEnterDocumentVisitor(e)
+	walker.RegisterEnterScalarTypeExtensionVisitor(e)
+}
+
+func (e *extendScalarTypeDefinitionVisitor) EnterDocument(operation, _ *ast.Document) {
+	e.document = operation
+}
+
+func (e *extendScalarTypeDefinitionVisitor) EnterScalarTypeExtension(ref int) {
+	nodes, exists := e.document.Index.NodesByNameBytes(e.document.ScalarTypeExtensionNameBytes(ref))
+	if !exists {
+		return
+	}
+
+	hasExtended := false
+	for i := range nodes {
+		if nodes[i].Kind != ast.NodeKindScalarTypeDefinition {
+			continue
+		}
+		if hasExtended {
+			e.StopWithExternalErr(operationreport.ErrSharedTypesMustNotBeExtended(e.document.ScalarTypeExtensionNameString(ref)))
+			return
+		}
+		e.document.ExtendScalarTypeDefinitionByScalarTypeExtension(nodes[i].Ref, ref)
+		hasExtended = true
+	}
+	if !hasExtended {
+		e.StopWithExternalErr(operationreport.ErrExtensionOrphansMustResolveInSupergraph(e.document.ScalarTypeExtensionNameBytes(ref)))
+	}
+}

sdlmerge/sdlmerge.go

@@ -0,0 +1,205 @@
+package sdlmerge
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/asttransform"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/astvalidation"
+
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/ast"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/astnormalization"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/astparser"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/astprinter"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/astvisitor"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/operationreport"
+)
+
+const (
+	rootOperationTypeDefinitions = `
+		type Query {}
+		type Mutation {}
+		type Subscription {}
+	`
+
+	parseDocumentError = "parse graphql document string: %w"
+)
+
+type Visitor interface {
+	Register(walker *astvisitor.Walker)
+}
+
+func MergeAST(ast *ast.Document) error {
+	normalizer := normalizer{}
+	normalizer.setupWalkers()
+
+	return normalizer.normalize(ast)
+}
+
+func MergeSDLs(SDLs ...string) (string, error) {
+	rawDocs := make([]string, 0, len(SDLs)+1)
+	rawDocs = append(rawDocs, rootOperationTypeDefinitions)
+	rawDocs = append(rawDocs, SDLs...)
+	if validationError := validateSubgraphs(rawDocs[1:]); validationError != nil {
+		return "", validationError
+	}
+	if normalizationError := normalizeSubgraphs(rawDocs[1:]); normalizationError != nil {
+		return "", normalizationError
+	}
+
+	doc, report := astparser.ParseGraphqlDocumentString(strings.Join(rawDocs, "\n"))
+	if report.HasErrors() {
+		return "", fmt.Errorf("parse graphql document string: %w", report)
+	}
+
+	astnormalization.NormalizeSubgraphSDL(&doc, &report)
+	if report.HasErrors() {
+		return "", fmt.Errorf("merge ast: %w", report)
+	}
+
+	if err := MergeAST(&doc); err != nil {
+		return "", fmt.Errorf("merge ast: %w", err)
+	}
+
+	out, err := astprinter.PrintString(&doc)
+	if err != nil {
+		return "", fmt.Errorf("stringify schema: %w", err)
+	}
+
+	return out, nil
+}
+
+func validateSubgraphs(subgraphs []string) error {
+	validator := astvalidation.NewDefinitionValidator(
+		astvalidation.PopulatedTypeBodies(), astvalidation.KnownTypeNames(),
+	)
+	for _, subgraph := range subgraphs {
+		doc, report := astparser.ParseGraphqlDocumentString(subgraph)
+		if err := asttransform.MergeDefinitionWithBaseSchema(&doc); err != nil {
+			return err
+		}
+		if report.HasErrors() {
+			return fmt.Errorf(parseDocumentError, report)
+		}
+		validator.Validate(&doc, &report)
+		if report.HasErrors() {
+			return fmt.Errorf("validate schema: %w", report)
+		}
+	}
+	return nil
+}
+
+func normalizeSubgraphs(subgraphs []string) error {
+	subgraphNormalizer := astnormalization.NewSubgraphDefinitionNormalizer()
+	for i, subgraph := range subgraphs {
+		doc, report := astparser.ParseGraphqlDocumentString(subgraph)
+		if report.HasErrors() {
+			return fmt.Errorf(parseDocumentError, report)
+		}
+		subgraphNormalizer.NormalizeDefinition(&doc, &report)
+		if report.HasErrors() {
+			return fmt.Errorf("normalize schema: %w", report)
+		}
+		out, err := astprinter.PrintString(&doc)
+		if err != nil {
+			return fmt.Errorf("stringify schema: %w", err)
+		}
+		subgraphs[i] = out
+	}
+	return nil
+}
+
+type normalizer struct {
+	walkers []*astvisitor.Walker
+}
+
+type entitySet map[string]struct{}
+
+func (m *normalizer) setupWalkers() {
+	collectedEntities := make(entitySet)
+	visitorGroups := [][]Visitor{
+		{
+			newCollectEntitiesVisitor(collectedEntities),
+		},
+		{
+			newExtendEnumTypeDefinition(),
+			newExtendInputObjectTypeDefinition(),
+			newExtendInterfaceTypeDefinition(collectedEntities),
+			newExtendScalarTypeDefinition(),
+			newExtendUnionTypeDefinition(),
+			newExtendObjectTypeDefinition(collectedEntities),
+			newRemoveEmptyObjectTypeDefinition(),
+			newRemoveMergedTypeExtensions(),
+		},
+		// visitors for cleaning up federated duplicated fields and directives
+		{
+			newRemoveFieldDefinitions("external"),
+			newRemoveDuplicateFieldedSharedTypesVisitor(),
+			newRemoveDuplicateFieldlessSharedTypesVisitor(),
+			newMergeDuplicatedFieldsVisitor(),
+			newRemoveInterfaceDefinitionDirective("key"),
+			newRemoveObjectTypeDefinitionDirective("key"),
+			newRemoveFieldDefinitionDirective("provides", "requires"),
+		},
+	}
+
+	for _, visitorGroup := range visitorGroups {
+		walker := astvisitor.NewWalker(48)
+		for _, visitor := range visitorGroup {
+			visitor.Register(&walker)
+			m.walkers = append(m.walkers, &walker)
+		}
+	}
+}
+
+func (m *normalizer) normalize(operation *ast.Document) error {
+	report := operationreport.Report{}
+
+	for _, walker := range m.walkers {
+		walker.Walk(operation, nil, &report)
+		if report.HasErrors() {
+			return fmt.Errorf("walk: %w", report)
+		}
+	}
+
+	return nil
+}
+
+func (e entitySet) isExtensionForEntity(nameBytes []byte, directiveRefs []int, document *ast.Document) (bool, *operationreport.ExternalError) {
+	name := string(nameBytes)
+	hasDirectives := len(directiveRefs) > 0
+	if _, exists := e[name]; !exists {
+		if !hasDirectives || !isEntityExtension(directiveRefs, document) {
+			return false, nil
+		}
+		err := operationreport.ErrExtensionWithKeyDirectiveMustExtendEntity(name)
+		return false, &err
+	}
+	if !hasDirectives {
+		err := operationreport.ErrEntityExtensionMustHaveKeyDirective(name)
+		return false, &err
+	}
+	if isEntityExtension(directiveRefs, document) {
+		return true, nil
+	}
+	err := operationreport.ErrEntityExtensionMustHaveKeyDirective(name)
+	return false, &err
+}
+
+func isEntityExtension(directiveRefs []int, document *ast.Document) bool {
+	for _, directiveRef := range directiveRefs {
+		if document.DirectiveNameString(directiveRef) == "key" {
+			return true
+		}
+	}
+	return false
+}
+
+func multipleExtensionError(isEntity bool, nameBytes []byte) *operationreport.ExternalError {
+	if isEntity {
+		err := operationreport.ErrEntitiesMustNotBeDuplicated(string(nameBytes))
+		return &err
+	}
+	err := operationreport.ErrSharedTypesMustNotBeExtended(string(nameBytes))
+	return &err
+}

sdlmerge/shared_types.go

@@ -0,0 +1,167 @@
+package sdlmerge
+
+import "github.com/wundergraph/graphql-go-tools/v2/pkg/ast"
+
+type fieldlessSharedType interface {
+	areValuesIdentical(valueRefsToCompare []int) bool
+	valueRefs() []int
+	valueName(ref int) string
+}
+
+func createValueSet(f fieldlessSharedType) map[string]bool {
+	valueSet := make(map[string]bool)
+	for _, valueRef := range f.valueRefs() {
+		valueSet[f.valueName(valueRef)] = true
+	}
+	return valueSet
+}
+
+type fieldedSharedType struct {
+	document  *ast.Document
+	fieldKind ast.NodeKind
+	fieldRefs []int
+	fieldSet  map[string]int
+}
+
+func newFieldedSharedType(document *ast.Document, fieldKind ast.NodeKind, fieldRefs []int) fieldedSharedType {
+	f := fieldedSharedType{
+		document,
+		fieldKind,
+		fieldRefs,
+		nil,
+	}
+	f.createFieldSet()
+	return f
+}
+
+func (f fieldedSharedType) areFieldsIdentical(fieldRefsToCompare []int) bool {
+	if len(f.fieldRefs) != len(fieldRefsToCompare) {
+		return false
+	}
+	for _, fieldRef := range fieldRefsToCompare {
+		actualFieldName := f.fieldName(fieldRef)
+		expectedTypeRef, exists := f.fieldSet[actualFieldName]
+		if !exists {
+			return false
+		}
+		actualTypeRef := f.fieldTypeRef(fieldRef)
+		if !f.document.TypesAreCompatibleDeep(expectedTypeRef, actualTypeRef) {
+			return false
+		}
+	}
+	return true
+}
+
+func (f *fieldedSharedType) createFieldSet() {
+	fieldSet := make(map[string]int)
+	for _, fieldRef := range f.fieldRefs {
+		fieldSet[f.fieldName(fieldRef)] = f.fieldTypeRef(fieldRef)
+	}
+	f.fieldSet = fieldSet
+}
+
+func (f fieldedSharedType) fieldName(ref int) string {
+	switch f.fieldKind {
+	case ast.NodeKindInputValueDefinition:
+		return f.document.InputValueDefinitionNameString(ref)
+	default:
+		return f.document.FieldDefinitionNameString(ref)
+	}
+}
+
+func (f fieldedSharedType) fieldTypeRef(ref int) int {
+	switch f.fieldKind {
+	case ast.NodeKindInputValueDefinition:
+		return f.document.InputValueDefinitions[ref].Type
+	default:
+		return f.document.FieldDefinitions[ref].Type
+	}
+}
+
+type enumSharedType struct {
+	*ast.EnumTypeDefinition
+	document *ast.Document
+	valueSet map[string]bool
+}
+
+func newEnumSharedType(document *ast.Document, ref int) enumSharedType {
+	e := enumSharedType{
+		&document.EnumTypeDefinitions[ref],
+		document,
+		nil,
+	}
+	e.valueSet = createValueSet(e)
+	return e
+}
+
+func (e enumSharedType) areValuesIdentical(valueRefsToCompare []int) bool {
+	if len(e.valueRefs()) != len(valueRefsToCompare) {
+		return false
+	}
+	for _, valueRefToCompare := range valueRefsToCompare {
+		name := e.valueName(valueRefToCompare)
+		if !e.valueSet[name] {
+			return false
+		}
+	}
+	return true
+}
+
+func (e enumSharedType) valueRefs() []int {
+	return e.EnumValuesDefinition.Refs
+}
+
+func (e enumSharedType) valueName(ref int) string {
+	return e.document.EnumValueDefinitionNameString(ref)
+}
+
+type unionSharedType struct {
+	*ast.UnionTypeDefinition
+	document *ast.Document
+	valueSet map[string]bool
+}
+
+func newUnionSharedType(document *ast.Document, ref int) unionSharedType {
+	u := unionSharedType{
+		&document.UnionTypeDefinitions[ref],
+		document,
+		nil,
+	}
+	u.valueSet = createValueSet(u)
+	return u
+}
+
+func (u unionSharedType) areValuesIdentical(valueRefsToCompare []int) bool {
+	if len(u.valueRefs()) != len(valueRefsToCompare) {
+		return false
+	}
+	for _, refToCompare := range valueRefsToCompare {
+		name := u.valueName(refToCompare)
+		if !u.valueSet[name] {
+			return false
+		}
+	}
+	return true
+}
+
+func (u unionSharedType) valueRefs() []int {
+	return u.UnionMemberTypes.Refs
+}
+
+func (u unionSharedType) valueName(ref int) string {
+	return u.document.TypeNameString(ref)
+}
+
+type scalarSharedType struct{}
+
+func (_ scalarSharedType) areValuesIdentical(_ []int) bool {
+	return true
+}
+
+func (_ scalarSharedType) valueRefs() []int {
+	return nil
+}
+
+func (_ scalarSharedType) valueName(_ int) string {
+	return ""
+}

sdlmerge/union_type_extending.go

@@ -0,0 +1,50 @@
+package sdlmerge
+
+import (
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/ast"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/astvisitor"
+	"github.com/wundergraph/graphql-go-tools/v2/pkg/operationreport"
+)
+
+func newExtendUnionTypeDefinition() *extendUnionTypeDefinitionVisitor {
+	return &extendUnionTypeDefinitionVisitor{}
+}
+
+type extendUnionTypeDefinitionVisitor struct {
+	*astvisitor.Walker
+	document *ast.Document
+}
+
+func (e *extendUnionTypeDefinitionVisitor) Register(walker *astvisitor.Walker) {
+	e.Walker = walker
+	walker.RegisterEnterDocumentVisitor(e)
+	walker.RegisterEnterUnionTypeExtensionVisitor(e)
+}
+
+func (e *extendUnionTypeDefinitionVisitor) EnterDocument(operation, _ *ast.Document) {
+	e.document = operation
+}
+
+func (e *extendUnionTypeDefinitionVisitor) EnterUnionTypeExtension(ref int) {
+	nodes, exists := e.document.Index.NodesByNameBytes(e.document.UnionTypeExtensionNameBytes(ref))
+	if !exists {
+		return
+	}
+
+	hasExtended := false
+	for i := range nodes {
+		if nodes[i].Kind != ast.NodeKindUnionTypeDefinition {
+			continue
+		}
+		if hasExtended {
+			e.StopWithExternalErr(operationreport.ErrSharedTypesMustNotBeExtended(e.document.UnionTypeExtensionNameString(ref)))
+			return
+		}
+		e.document.ExtendUnionTypeDefinitionByUnionTypeExtension(nodes[i].Ref, ref)
+		hasExtended = true
+	}
+
+	if !hasExtended {
+		e.StopWithExternalErr(operationreport.ErrExtensionOrphansMustResolveInSupergraph(e.document.UnionTypeExtensionNameBytes(ref)))
+	}
+}