introduce ast.Path type

ast/path.go

@@ -0,0 +1,42 @@
+package ast
+
+import (
+	"bytes"
+	"fmt"
+)
+
+type Path []PathElement
+
+type PathElement interface {
+	isPathElement()
+}
+
+var _ PathElement = PathIndex(0)
+var _ PathElement = PathName("")
+
+func (path Path) String() string {
+	var str bytes.Buffer
+	for i, v := range path {
+
+		switch v := v.(type) {
+		case PathIndex:
+			str.WriteString(fmt.Sprintf("[%d]", v))
+		case PathName:
+			if i != 0 {
+				str.WriteByte('.')
+			}
+			str.WriteString(string(v))
+		default:
+			panic(fmt.Sprintf("unknown type: %T", v))
+		}
+	}
+	return str.String()
+}
+
+type PathIndex int
+
+func (_ PathIndex) isPathElement() {}
+
+type PathName string
+
+func (_ PathName) isPathElement() {}

ast/source.go

@@ -3,13 +3,13 @@ package ast
 // Source covers a single *.graphql file
 type Source struct {
 	// Name is the filename of the source
-	Name    string
+	Name string
 	// Input is the actual contents of the source file
-	Input   string
+	Input string
 	// BuiltIn indicate whether the source is a part of the specification
 	BuiltIn bool
 }
- 
+
 type Position struct {
 	Start  int     // The starting position, in runes, of this token in the input.
 	End    int     // The end position, in runes, of this token in the input.

gqlerror/error.go

@@ -11,7 +11,7 @@ import (
 // Error is the standard graphql error type described in https://facebook.github.io/graphql/draft/#sec-Errors
 type Error struct {
 	Message    string                 `json:"message"`
-	Path       []interface{}          `json:"path,omitempty"`
+	Path       ast.Path               `json:"path,omitempty"`
 	Locations  []Location             `json:"locations,omitempty"`
 	Extensions map[string]interface{} `json:"extensions,omitempty"`
 	Rule       string                 `json:"-"`
@@ -63,20 +63,7 @@ func (err *Error) Error() string {
 }
 
 func (err Error) pathString() string {
-	var str bytes.Buffer
-	for i, v := range err.Path {
-
-		switch v := v.(type) {
-		case int, int64:
-			str.WriteString(fmt.Sprintf("[%d]", v))
-		default:
-			if i != 0 {
-				str.WriteByte('.')
-			}
-			str.WriteString(fmt.Sprint(v))
-		}
-	}
-	return str.String()
+	return err.Path.String()
 }
 
 func (errs List) Error() string {
@@ -88,7 +75,7 @@ func (errs List) Error() string {
 	return buf.String()
 }
 
-func WrapPath(path []interface{}, err error) *Error {
+func WrapPath(path ast.Path, err error) *Error {
 	return &Error{
 		Message: err.Error(),
 		Path:    path,
@@ -101,7 +88,7 @@ func Errorf(message string, args ...interface{}) *Error {
 	}
 }
 
-func ErrorPathf(path []interface{}, message string, args ...interface{}) *Error {
+func ErrorPathf(path ast.Path, message string, args ...interface{}) *Error {
 	return &Error{
 		Message: fmt.Sprintf(message, args...),
 		Path:    path,

gqlerror/error_test.go

@@ -4,6 +4,7 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/require"
+	"github.com/vektah/gqlparser/ast"
 )
 
 func TestErrorFormatting(t *testing.T) {
@@ -22,7 +23,7 @@ func TestErrorFormatting(t *testing.T) {
 	})
 
 	t.Run("with path", func(t *testing.T) {
-		err := ErrorPathf([]interface{}{"a", 1, "b"}, "kabloom")
+		err := ErrorPathf(ast.Path{ast.PathName("a"), ast.PathIndex(1), ast.PathName("b")}, "kabloom")
 
 		require.Equal(t, `input: a[1].b kabloom`, err.Error())
 	})

validator/vars.go

@@ -17,12 +17,12 @@ func VariableValues(schema *ast.Schema, op *ast.OperationDefinition, variables m
 	coercedVars := map[string]interface{}{}
 
 	validator := varValidator{
-		path:   []interface{}{"variable"},
+		path:   ast.Path{ast.PathName("variable")},
 		schema: schema,
 	}
 
 	for _, v := range op.VariableDefinitions {
-		validator.path = append(validator.path, v.Variable)
+		validator.path = append(validator.path, ast.PathName(v.Variable))
 
 		if !v.Definition.IsInputType() {
 			return nil, gqlerror.ErrorPathf(validator.path, "must an input type")
@@ -69,7 +69,7 @@ func VariableValues(schema *ast.Schema, op *ast.OperationDefinition, variables m
 }
 
 type varValidator struct {
-	path   []interface{}
+	path   ast.Path
 	schema *ast.Schema
 }
 
@@ -87,7 +87,7 @@ func (v *varValidator) validateVarType(typ *ast.Type, val reflect.Value) *gqlerr
 
 		for i := 0; i < val.Len(); i++ {
 			resetPath()
-			v.path = append(v.path, i)
+			v.path = append(v.path, ast.PathIndex(i))
 			field := val.Index(i)
 
 			if field.Kind() == reflect.Ptr || field.Kind() == reflect.Interface {
@@ -171,7 +171,7 @@ func (v *varValidator) validateVarType(typ *ast.Type, val reflect.Value) *gqlerr
 			val.MapIndex(name)
 			fieldDef := def.Fields.ForName(name.String())
 			resetPath()
-			v.path = append(v.path, name.String())
+			v.path = append(v.path, ast.PathName(name.String()))
 
 			if fieldDef == nil {
 				return gqlerror.ErrorPathf(v.path, "unknown field")
@@ -180,7 +180,7 @@ func (v *varValidator) validateVarType(typ *ast.Type, val reflect.Value) *gqlerr
 
 		for _, fieldDef := range def.Fields {
 			resetPath()
-			v.path = append(v.path, fieldDef.Name)
+			v.path = append(v.path, ast.PathName(fieldDef.Name))
 
 			field := val.MapIndex(reflect.ValueOf(fieldDef.Name))
 			if !field.IsValid() {