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/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
+}