Merge pull request #493 from bhoriuchi/master

adds a field sort by source location before executing serially

executor.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"reflect"
+	"sort"
 	"strings"
 
 	"github.com/graphql-go/graphql/gqlerrors"
@@ -254,7 +255,9 @@ func executeFieldsSerially(p executeFieldsParams) *Result {
 	}
 
 	finalResults := make(map[string]interface{}, len(p.Fields))
-	for responseName, fieldASTs := range p.Fields {
+	for _, orderedField := range orderedFields(p.Fields) {
+		responseName := orderedField.responseName
+		fieldASTs := orderedField.fieldASTs
 		fieldPath := p.Path.WithKey(responseName)
 		resolved, state := resolveField(p.ExecutionContext, p.ParentType, p.Source, fieldASTs, fieldPath)
 		if state.hasNoFieldDefs {
@@ -1038,3 +1041,39 @@ func getFieldDef(schema Schema, parentType *Object, fieldName string) *FieldDefi
 	}
 	return parentType.Fields()[fieldName]
 }
+
+// contains field information that will be placed in an ordered slice
+type orderedField struct {
+	responseName string
+	fieldASTs    []*ast.Field
+}
+
+// orders fields from a fields map by location in the source
+func orderedFields(fields map[string][]*ast.Field) []*orderedField {
+	orderedFields := []*orderedField{}
+	fieldMap := map[int]*orderedField{}
+	startLocs := []int{}
+
+	for responseName, fieldASTs := range fields {
+		// find the lowest location in the current fieldASTs
+		lowest := -1
+		for _, fieldAST := range fieldASTs {
+			loc := fieldAST.GetLoc().Start
+			if lowest == -1 || loc < lowest {
+				lowest = loc
+			}
+		}
+		startLocs = append(startLocs, lowest)
+		fieldMap[lowest] = &orderedField{
+			responseName: responseName,
+			fieldASTs:    fieldASTs,
+		}
+	}
+
+	sort.Ints(startLocs)
+	for _, startLoc := range startLocs {
+		orderedFields = append(orderedFields, fieldMap[startLoc])
+	}
+
+	return orderedFields
+}