Added support of custom directives

example/caching/server/server.go

@@ -9,6 +9,7 @@ import (
 	"github.com/graph-gophers/graphql-go"
 	"github.com/graph-gophers/graphql-go/example/caching"
 	"github.com/graph-gophers/graphql-go/example/caching/cache"
+	"github.com/graph-gophers/graphql-go/pkg/common"
 )
 
 var schema *graphql.Schema
@@ -40,12 +41,12 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	var hint *cache.Hint
 	if cacheable(r) {
 		ctx, hints, done := cache.Hintable(r.Context())
-		response = h.Schema.Exec(ctx, p.Query, p.OperationName, p.Variables)
+		response = h.Schema.Exec(ctx, p.Query, p.OperationName, p.Variables, map[string]common.DirectiveVisitor{})
 		done()
 		v := <-hints
 		hint = &v
 	} else {
-		response = h.Schema.Exec(r.Context(), p.Query, p.OperationName, p.Variables)
+		response = h.Schema.Exec(r.Context(), p.Query, p.OperationName, p.Variables, map[string]common.DirectiveVisitor{})
 	}
 	responseJSON, err := json.Marshal(response)
 	if err != nil {

gqltesting/testing.go

@@ -12,18 +12,20 @@ import (
 
 	graphql "github.com/graph-gophers/graphql-go"
 	"github.com/graph-gophers/graphql-go/errors"
+	"github.com/graph-gophers/graphql-go/pkg/common"
 )
 
 // Test is a GraphQL test case to be used with RunTest(s).
 type Test struct {
-	Context        context.Context
-	Schema         *graphql.Schema
-	Query          string
-	OperationName  string
-	Variables      map[string]interface{}
-	ExpectedResult string
-	ExpectedErrors []*errors.QueryError
-	RawResponse    bool
+	Context           context.Context
+	Schema            *graphql.Schema
+	Query             string
+	OperationName     string
+	Variables         map[string]interface{}
+	ExpectedResult    string
+	ExpectedErrors    []*errors.QueryError
+	RawResponse       bool
+	DirectiveVisitors map[string]common.DirectiveVisitor
 }
 
 // RunTests runs the given GraphQL test cases as subtests.
@@ -45,7 +47,7 @@ func RunTest(t *testing.T, test *Test) {
 	if test.Context == nil {
 		test.Context = context.Background()
 	}
-	result := test.Schema.Exec(test.Context, test.Query, test.OperationName, test.Variables)
+	result := test.Schema.Exec(test.Context, test.Query, test.OperationName, test.Variables, test.DirectiveVisitors)
 
 	checkErrors(t, test.ExpectedErrors, result.Errors)
 

graphql.go

@@ -8,7 +8,6 @@ import (
 	"time"
 
 	"github.com/graph-gophers/graphql-go/errors"
-	"github.com/graph-gophers/graphql-go/internal/common"
 	"github.com/graph-gophers/graphql-go/internal/exec"
 	"github.com/graph-gophers/graphql-go/internal/exec/resolvable"
 	"github.com/graph-gophers/graphql-go/internal/exec/selected"
@@ -17,6 +16,7 @@ import (
 	"github.com/graph-gophers/graphql-go/internal/validation"
 	"github.com/graph-gophers/graphql-go/introspection"
 	"github.com/graph-gophers/graphql-go/log"
+	"github.com/graph-gophers/graphql-go/pkg/common"
 	"github.com/graph-gophers/graphql-go/trace"
 )
 
@@ -181,14 +181,14 @@ func (s *Schema) ValidateWithVariables(queryString string, variables map[string]
 // Exec executes the given query with the schema's resolver. It panics if the schema was created
 // without a resolver. If the context get cancelled, no further resolvers will be called and a
 // the context error will be returned as soon as possible (not immediately).
-func (s *Schema) Exec(ctx context.Context, queryString string, operationName string, variables map[string]interface{}) *Response {
+func (s *Schema) Exec(ctx context.Context, queryString string, operationName string, variables map[string]interface{}, visitors map[string]common.DirectiveVisitor) *Response {
 	if s.res.Resolver == (reflect.Value{}) {
 		panic("schema created without resolver, can not exec")
 	}
-	return s.exec(ctx, queryString, operationName, variables, s.res)
+	return s.exec(ctx, queryString, operationName, variables, visitors, s.res)
 }
 
-func (s *Schema) exec(ctx context.Context, queryString string, operationName string, variables map[string]interface{}, res *resolvable.Schema) *Response {
+func (s *Schema) exec(ctx context.Context, queryString string, operationName string, variables map[string]interface{}, visitors map[string]common.DirectiveVisitor, res *resolvable.Schema) *Response {
 	doc, qErr := query.Parse(queryString)
 	if qErr != nil {
 		return &Response{Errors: []*errors.QueryError{qErr}}
@@ -239,9 +239,10 @@ func (s *Schema) exec(ctx context.Context, queryString string, operationName str
 			Schema:               s.schema,
 			DisableIntrospection: s.disableIntrospection,
 		},
-		Limiter: make(chan struct{}, s.maxParallelism),
-		Tracer:  s.tracer,
-		Logger:  s.logger,
+		Limiter:  make(chan struct{}, s.maxParallelism),
+		Tracer:   s.tracer,
+		Logger:   s.logger,
+		Visitors: visitors,
 	}
 	varTypes := make(map[string]*introspection.Type)
 	for _, v := range op.Vars {

graphql_test.go

@@ -11,6 +11,7 @@ import (
 	gqlerrors "github.com/graph-gophers/graphql-go/errors"
 	"github.com/graph-gophers/graphql-go/example/starwars"
 	"github.com/graph-gophers/graphql-go/gqltesting"
+	"github.com/graph-gophers/graphql-go/pkg/common"
 )
 
 type helloWorldResolver1 struct{}
@@ -45,6 +46,20 @@ func (r *helloSnakeResolver2) SayHello(ctx context.Context, args struct{ FullNam
 	return "Hello " + args.FullName + "!", nil
 }
 
+type customDirectiveVisitor struct{}
+
+func (v customDirectiveVisitor) Before(directive *common.Directive, input interface{}) error {
+	return nil
+}
+
+func (v customDirectiveVisitor) After(directive *common.Directive, output interface{}) (interface{}, error) {
+	if value, ok := directive.Args.Get("customAttribute"); ok {
+		return fmt.Sprintf("Directive '%s' (with arg '%s') modified result: %s", directive.Name.Name, value.String(), output.(string)), nil
+	} else {
+		return fmt.Sprintf("Directive '%s' modified result: %s", directive.Name.Name, output.(string)), nil
+	}
+}
+
 type theNumberResolver struct {
 	number int32
 }
@@ -213,6 +228,67 @@ func TestHelloWorld(t *testing.T) {
 	})
 }
 
+func TestCustomDirective(t *testing.T) {
+	t.Parallel()
+
+	gqltesting.RunTests(t, []*gqltesting.Test{
+		{
+			Schema: graphql.MustParseSchema(`
+				directive @customDirective on FIELD_DEFINITION
+
+				schema {
+					query: Query
+				}
+
+				type Query {
+					hello_html: String! @customDirective
+				}
+			`, &helloSnakeResolver1{}),
+			Query: `
+				{
+					hello_html
+				}
+			`,
+			ExpectedResult: `
+				{
+					"hello_html": "Directive 'customDirective' modified result: Hello snake!"
+				}
+			`,
+			DirectiveVisitors: map[string]common.DirectiveVisitor{
+				"customDirective": customDirectiveVisitor{},
+			},
+		},
+		{
+			Schema: graphql.MustParseSchema(`
+				directive @customDirective(
+					customAttribute: String!
+			    ) on FIELD_DEFINITION
+
+				schema {
+					query: Query
+				}
+
+				type Query {
+					say_hello(full_name: String!): String! @customDirective(customAttribute: hi)
+				}
+			`, &helloSnakeResolver1{}),
+			Query: `
+				{
+					say_hello(full_name: "Johnny")
+				}
+			`,
+			ExpectedResult: `
+				{
+					"say_hello": "Directive 'customDirective' (with arg 'hi') modified result: Hello Johnny!"
+				}
+			`,
+			DirectiveVisitors: map[string]common.DirectiveVisitor{
+				"customDirective": customDirectiveVisitor{},
+			},
+		},
+	})
+}
+
 func TestHelloSnake(t *testing.T) {
 	t.Parallel()
 
@@ -3728,7 +3804,7 @@ func TestSchema_Exec_without_resolver(t *testing.T) {
 					t.Fail()
 				}
 			}()
-			_ = s.Exec(context.Background(), tt.Args.Query, "", map[string]interface{}{})
+			_ = s.Exec(context.Background(), tt.Args.Query, "", map[string]interface{}{}, map[string]common.DirectiveVisitor{})
 		})
 	}
 }

internal/exec/exec.go

@@ -10,12 +10,12 @@ import (
 	"time"
 
 	"github.com/graph-gophers/graphql-go/errors"
-	"github.com/graph-gophers/graphql-go/internal/common"
 	"github.com/graph-gophers/graphql-go/internal/exec/resolvable"
 	"github.com/graph-gophers/graphql-go/internal/exec/selected"
 	"github.com/graph-gophers/graphql-go/internal/query"
 	"github.com/graph-gophers/graphql-go/internal/schema"
 	"github.com/graph-gophers/graphql-go/log"
+	"github.com/graph-gophers/graphql-go/pkg/common"
 	"github.com/graph-gophers/graphql-go/trace"
 )
 
@@ -25,6 +25,7 @@ type Request struct {
 	Tracer                   trace.Tracer
 	Logger                   log.Logger
 	SubscribeResolverTimeout time.Duration
+	Visitors                 map[string]common.DirectiveVisitor
 }
 
 func (r *Request) handlePanic(ctx context.Context) {
@@ -207,8 +208,42 @@ func execFieldSelection(ctx context.Context, r *Request, s *resolvable.Schema, f
 			if f.field.ArgsPacker != nil {
 				in = append(in, f.field.PackedArgs)
 			}
+
+			// Before hook directive visitor
+			if len(f.field.Directives) > 0 {
+				for _, directive := range f.field.Directives {
+					if visitor, ok := r.Visitors[directive.Name.Name]; ok {
+						var values = make([]interface{}, 0)
+						for _, inValue := range in {
+							values = append(values, inValue.Interface())
+						}
+
+						if err := visitor.Before(directive, values); err != nil {
+							return nil
+						}
+					}
+				}
+			}
+
+			// Call method
 			callOut := res.Method(f.field.MethodIndex).Call(in)
 			result = callOut[0]
+
+			// After hook directive visitor (when no error is returned from resolver)
+			if !f.field.HasError && len(f.field.Directives) > 0 {
+				for _, directive := range f.field.Directives {
+					if visitor, ok := r.Visitors[directive.Name.Name]; ok {
+						returned, err := visitor.After(directive, result.Interface())
+						if err != nil {
+							f.field.HasError = true
+							callOut[1] = reflect.ValueOf(err)
+						} else {
+							result = reflect.ValueOf(returned)
+						}
+					}
+				}
+			}
+
 			if f.field.HasError && !callOut[1].IsNil() {
 				resolverErr := callOut[1].Interface().(error)
 				err := errors.Errorf("%s", resolverErr)

internal/exec/packer/packer.go

@@ -7,8 +7,8 @@ import (
 	"strings"
 
 	"github.com/graph-gophers/graphql-go/errors"
-	"github.com/graph-gophers/graphql-go/internal/common"
 	"github.com/graph-gophers/graphql-go/internal/schema"
+	"github.com/graph-gophers/graphql-go/pkg/common"
 )
 
 type packer interface {

internal/exec/resolvable/meta.go

@@ -4,9 +4,9 @@ import (
 	"fmt"
 	"reflect"
 
-	"github.com/graph-gophers/graphql-go/internal/common"
 	"github.com/graph-gophers/graphql-go/internal/schema"
 	"github.com/graph-gophers/graphql-go/introspection"
+	"github.com/graph-gophers/graphql-go/pkg/common"
 )
 
 // Meta defines the details of the metadata schema for introspection.

internal/exec/resolvable/resolvable.go

@@ -6,9 +6,9 @@ import (
 	"reflect"
 	"strings"
 
-	"github.com/graph-gophers/graphql-go/internal/common"
 	"github.com/graph-gophers/graphql-go/internal/exec/packer"
 	"github.com/graph-gophers/graphql-go/internal/schema"
+	"github.com/graph-gophers/graphql-go/pkg/common"
 )
 
 type Schema struct {

internal/exec/selected/selected.go

@@ -6,12 +6,12 @@ import (
 	"sync"
 
 	"github.com/graph-gophers/graphql-go/errors"
-	"github.com/graph-gophers/graphql-go/internal/common"
 	"github.com/graph-gophers/graphql-go/internal/exec/packer"
 	"github.com/graph-gophers/graphql-go/internal/exec/resolvable"
 	"github.com/graph-gophers/graphql-go/internal/query"
 	"github.com/graph-gophers/graphql-go/internal/schema"
 	"github.com/graph-gophers/graphql-go/introspection"
+	"github.com/graph-gophers/graphql-go/pkg/common"
 )
 
 type Request struct {

internal/exec/subscribe.go

@@ -9,10 +9,10 @@ import (
 	"time"
 
 	"github.com/graph-gophers/graphql-go/errors"
-	"github.com/graph-gophers/graphql-go/internal/common"
 	"github.com/graph-gophers/graphql-go/internal/exec/resolvable"
 	"github.com/graph-gophers/graphql-go/internal/exec/selected"
 	"github.com/graph-gophers/graphql-go/internal/query"
+	"github.com/graph-gophers/graphql-go/pkg/common"
 )
 
 type Response struct {

internal/query/query.go

@@ -5,7 +5,7 @@ import (
 	"text/scanner"
 
 	"github.com/graph-gophers/graphql-go/errors"
-	"github.com/graph-gophers/graphql-go/internal/common"
+	"github.com/graph-gophers/graphql-go/pkg/common"
 )
 
 type Document struct {

internal/schema/schema.go

@@ -5,7 +5,7 @@ import (
 	"text/scanner"
 
 	"github.com/graph-gophers/graphql-go/errors"
-	"github.com/graph-gophers/graphql-go/internal/common"
+	"github.com/graph-gophers/graphql-go/pkg/common"
 )
 
 // Schema represents a GraphQL service's collective type system capabilities.

internal/schema/schema_internal_test.go

@@ -4,7 +4,7 @@ import (
 	"testing"
 
 	"github.com/graph-gophers/graphql-go/errors"
-	"github.com/graph-gophers/graphql-go/internal/common"
+	"github.com/graph-gophers/graphql-go/pkg/common"
 )
 
 func TestParseInterfaceDef(t *testing.T) {

internal/validation/validation.go

@@ -9,9 +9,9 @@ import (
 	"text/scanner"
 
 	"github.com/graph-gophers/graphql-go/errors"
-	"github.com/graph-gophers/graphql-go/internal/common"
 	"github.com/graph-gophers/graphql-go/internal/query"
 	"github.com/graph-gophers/graphql-go/internal/schema"
+	"github.com/graph-gophers/graphql-go/pkg/common"
 )
 
 type varSet map[*common.InputValue]struct{}

introspection.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/graph-gophers/graphql-go/internal/exec/resolvable"
 	"github.com/graph-gophers/graphql-go/introspection"
+	"github.com/graph-gophers/graphql-go/pkg/common"
 )
 
 // Inspect allows inspection of the given schema.
@@ -15,7 +16,7 @@ func (s *Schema) Inspect() *introspection.Schema {
 
 // ToJSON encodes the schema in a JSON format used by tools like Relay.
 func (s *Schema) ToJSON() ([]byte, error) {
-	result := s.exec(context.Background(), introspectionQuery, "", nil, &resolvable.Schema{
+	result := s.exec(context.Background(), introspectionQuery, "", nil, map[string]common.DirectiveVisitor{}, &resolvable.Schema{
 		Meta:   s.res.Meta,
 		Query:  &resolvable.Object{},
 		Schema: *s.schema,