Merge pull request #5 from DealTap/expose-selection-tree

Expose selected fields in resolver context

Author: 0xSalman

example/social/social.go

@@ -2,9 +2,12 @@ package social
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"strings"
 	"time"
+
+	"github.com/graph-gophers/graphql-go/selected"
 )
 
 const Schema = `
@@ -51,8 +54,8 @@ const Schema = `
 `
 
 type page struct {
-	First *int
-	Last  *int
+	First *float64
+	Last  *float64
 }
 
 type admin interface {
@@ -101,11 +104,14 @@ func (u user) FriendsResolver(args struct{ Page *page }) (*[]*user, error) {
 
 	if args.Page != nil {
 		if args.Page.First != nil {
-			from = *args.Page.First
+			from = int(*args.Page.First)
+			if from > numFriends {
+				return nil, errors.New("not enough users")
+			}
 		}
 		if args.Page.Last != nil {
-			to = *args.Page.Last
-			if to > numFriends {
+			to = int(*args.Page.Last)
+			if to == 0 || to > numFriends {
 				to = numFriends
 			}
 		}
@@ -183,6 +189,12 @@ func (r *Resolver) Admin(ctx context.Context, args struct {
 }
 
 func (r *Resolver) User(ctx context.Context, args struct{ Id string }) (user, error) {
+	selectedFields, _ := selected.GetFieldsFromContext(ctx)
+	for _, field := range selectedFields {
+		// TODO temporary until unit test are added
+		fmt.Printf("name=%s, selectedChildren=%v, args=%v\n", field.Name, len(field.Selected) > 0, field.Args)
+	}
+
 	if usr, ok := usersMap[args.Id]; ok {
 		return *usr, nil
 	}

internal/exec/exec.go

@@ -14,6 +14,7 @@ import (
 	"github.com/graph-gophers/graphql-go/internal/query"
 	"github.com/graph-gophers/graphql-go/internal/schema"
 	"github.com/graph-gophers/graphql-go/log"
+	pubselected "github.com/graph-gophers/graphql-go/selected"
 	"github.com/graph-gophers/graphql-go/trace"
 )
 
@@ -176,7 +177,9 @@ func execFieldSelection(ctx context.Context, r *Request, f *fieldToExec, path *p
 		if f.field.MethodIndex != -1 {
 			var in []reflect.Value
 			if f.field.HasContext {
-				in = append(in, reflect.ValueOf(traceCtx))
+				// lazily evaluate
+				resCtx := context.WithValue(traceCtx, pubselected.ContextKey, selectedFields(f.sels))
+				in = append(in, reflect.ValueOf(resCtx))
 			}
 			if f.field.ArgsPacker != nil {
 				in = append(in, f.field.PackedArgs)
@@ -301,6 +304,32 @@ func unwrapNonNull(t common.Type) (common.Type, bool) {
 	return t, false
 }
 
+// lazily add selection fields in context
+func selectedFields(sels []selected.Selection) pubselected.SelectedFields {
+	return func() []pubselected.SelectedField {
+		return selectionToSelectedFields(sels)
+	}
+}
+
+func selectionToSelectedFields(sels []selected.Selection) []pubselected.SelectedField {
+	var selectedFields []pubselected.SelectedField
+	selsLen := len(sels)
+	if selsLen != 0 {
+		selectedFields = make([]pubselected.SelectedField, 0, selsLen)
+		for _, sel := range sels {
+			selField, ok := sel.(*selected.SchemaField)
+			if ok {
+				selectedFields = append(selectedFields, pubselected.SelectedField{
+					Name:     selField.Field.Name,
+					Args:     selField.Args,
+					Selected: selectionToSelectedFields(selField.Sels),
+				})
+			}
+		}
+	}
+	return selectedFields
+}
+
 type pathSegment struct {
 	parent *pathSegment
 	value  interface{}

selected/selected.go

@@ -0,0 +1,26 @@
+package selected
+
+import (
+	"context"
+	"errors"
+)
+
+const ContextKey = "Resolver_Selected_Fields"
+
+type SelectedFields func() []SelectedField
+
+type SelectedField struct {
+	Name     string
+	Args     map[string]interface{}
+	Selected []SelectedField
+}
+
+func GetFieldsFromContext(ctx context.Context) (fields []SelectedField, err error) {
+	fieldsFunc, ok := ctx.Value(ContextKey).(SelectedFields)
+	if ok == false {
+		err = errors.New("could not get graphql fields from context")
+		return
+	}
+	fields = fieldsFunc()
+	return
+}