Add support for generating code which returns errors on unknown fields

errors.go

@@ -86,3 +86,21 @@ func (err InvalidUsagePooledEncoderError) Error() string {
 // ErrUnmarshalPtrExpected is the error returned when unmarshal expects a pointer value,
 // When using `dec.ObjectNull` or `dec.ArrayNull` for example.
 var ErrUnmarshalPtrExpected = errors.New("Cannot unmarshal to given value, a pointer is expected")
+
+const unknownFieldErrorMsg = "Encountered unknown field %q while unmarshal JSON to type '%T'"
+
+// UnknownFieldError occurs when Decoding a object with a unknown field.
+type UnknownFieldError string
+
+func (err UnknownFieldError) Error() string {
+	return string(err)
+}
+func MakeUnknownFieldErr(v interface{}, key string) error {
+	return UnknownFieldError(
+		fmt.Sprintf(
+			unknownFieldErrorMsg,
+			key,
+			v,
+		),
+	)
+}

gojay/README.md

@@ -23,7 +23,11 @@ If you just want to the output to stdout, omit the -o flag.
 - t Types to generate with all its dependencies (comma separated)
 - a Annotation tag used to read metadata (default: json)
 - o Output file (relative or absolute path)
+
+Flags that alter the generated code:
+
 - p Pool to reuse object (using sync.Pool)
+- e Return a error on unknown fields (default: false)
 
 Examples:
 

gojay/codegen/generator_test.go

@@ -1,11 +1,12 @@
 package codegen
 
 import (
-	"github.com/stretchr/testify/assert"
-	"github.com/viant/toolbox"
 	"log"
 	"path"
 	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/viant/toolbox"
 )
 
 func TestGenerator_Generate(t *testing.T) {
@@ -45,7 +46,7 @@ func TestGenerator_Generate(t *testing.T) {
 			},
 		},
 		{
-			description: "struct with json annotation and time/foarmat|layouat generation",
+			description: "struct with json annotation and time/format|layout generation",
 			options: &Options{
 				Source:      path.Join(parent, "annotated_struct"),
 				Types:       []string{"Message"},
@@ -54,6 +55,15 @@ func TestGenerator_Generate(t *testing.T) {
 				TagName:     "json",
 			},
 		},
+		{
+			description: "basic struct code generation with unknown field errors",
+			options: &Options{
+				Source:       path.Join(parent, "unknown_struct"),
+				Types:        []string{"Message"},
+				Dest:         path.Join(parent, "unknown_struct", "encoding.go"),
+				ErrOnUnknown: true,
+			},
+		},
 	}
 
 	for _, useCase := range useCases {

gojay/codegen/options.go

@@ -10,12 +10,13 @@ import (
 )
 
 type Options struct {
-	Source      string
-	Dest        string
-	Types       []string
-	PoolObjects bool
-	TagName     string
-	Pkg         string
+	Source       string
+	Dest         string
+	Types        []string
+	PoolObjects  bool
+	TagName      string
+	Pkg          string
+	ErrOnUnknown bool
 }
 
 func (o *Options) Validate() error {
@@ -29,12 +30,13 @@ func (o *Options) Validate() error {
 }
 
 const (
-	optionKeySource      = "s"
-	optionKeyDest        = "o"
-	optionKeyTypes       = "t"
-	optionKeyTagName     = "a"
-	optionKeyPoolObjects = "p"
-	optionKeyPkg         = "pkg"
+	optionKeySource       = "s"
+	optionKeyDest         = "o"
+	optionKeyTypes        = "t"
+	optionKeyTagName      = "a"
+	optionKeyPoolObjects  = "p"
+	optionKeyPkg          = "pkg"
+	optionKeyErrOnUnknown = "e"
 )
 
 //NewOptionsWithFlagSet creates a new options for the supplide flagset
@@ -48,6 +50,7 @@ func NewOptionsWithFlagSet(set *flag.FlagSet) *Options {
 	result.TagName = set.Lookup(optionKeyTagName).Value.String()
 	result.Types = strings.Split(set.Lookup(optionKeyTypes).Value.String(), ",")
 	result.Pkg = set.Lookup(optionKeyPkg).Value.String()
+	result.ErrOnUnknown = toolbox.AsBoolean(set.Lookup(optionKeyErrOnUnknown).Value.String())
 	if result.Source == "" {
 		result.Source = url.NewResource(".").ParsedURL.Path
 	}

gojay/codegen/struct.go

@@ -46,6 +46,7 @@ func (s *Struct) generateEncoding(structInfo *toolbox.TypeInfo) (string, error)
 		DecodingCases string
 		Reset         string
 		FieldCount    int
+		ErrOnUnknown  bool
 	}{
 		Receiver:      s.Alias + " *" + s.Name,
 		DecodingCases: strings.Join(decodingCases, "\n"),
@@ -54,6 +55,7 @@ func (s *Struct) generateEncoding(structInfo *toolbox.TypeInfo) (string, error)
 		InitEmbedded:  initEmbedded,
 		Reset:         resetCode,
 		Alias:         s.Alias,
+		ErrOnUnknown:  s.options.ErrOnUnknown,
 	}
 	return expandBlockTemplate(encodingStructType, data)
 }

gojay/codegen/template.go

@@ -174,13 +174,23 @@ func ({{.Receiver}}) IsNil() bool {
 func ({{.Receiver}}) UnmarshalJSONObject(dec *gojay.Decoder, k string) error {
 {{.InitEmbedded}}
 	switch k {
-{{.DecodingCases}}	
+{{.DecodingCases}}
+{{if .ErrOnUnknown}}
+	default:
+		return gojay.MakeUnknownFieldErr({{.Alias}}, k)
+{{end}}
 	}
 	return nil
 }
 
 // NKeys returns the number of keys to unmarshal
-func ({{.Receiver}}) NKeys() int { return {{.FieldCount}} }
+func ({{.Receiver}}) NKeys() int {
+{{- if .ErrOnUnknown}}
+	return 0 // Unmarshal all keys so we can catch trailing unknown keys.
+{{else}}
+	return {{.FieldCount}}
+{{end -}}
+}
 
 {{.Reset}}
 
@@ -305,7 +315,7 @@ func expandTemplate(namespace string, dictionary map[int]string, key int, data i
 	}
 	temlate, err := template.New(id).Parse(textTemplate)
 	if err != nil {
-		return "", fmt.Errorf("fiailed to parse template %v %v, due to %v", namespace, key, err)
+		return "", fmt.Errorf("failed to parse template %v %v, due to %v", namespace, key, err)
 	}
 	writer := new(bytes.Buffer)
 	err = temlate.Execute(writer, data)

gojay/codegen/test/unknown_struct/encoding_test.go

@@ -0,0 +1,27 @@
+package unknown_struct
+
+import (
+	"testing"
+
+	"github.com/francoispqt/gojay"
+	"github.com/stretchr/testify/require"
+)
+
+var msg = &Message{
+	Id:   1022,
+	Name: "name acc",
+}
+
+var jsonData = `{
+  "Id": 1022,
+  "Name": "name acc",
+  "Price": 13.3
+}`
+
+func TestMessage_Unmarshal(t *testing.T) {
+	var err error
+	var data = []byte(jsonData)
+	message := &Message{}
+	err = gojay.UnmarshalJSONObject(data, message)
+	require.EqualError(t, err, gojay.MakeUnknownFieldErr(message, "Price").Error())
+}

gojay/codegen/test/unknown_struct/message.go

@@ -0,0 +1,6 @@
+package unknown_struct
+
+type Message struct {
+	Id   int
+	Name string
+}

gojay/gojay.go

@@ -2,8 +2,9 @@ package main
 
 import (
 	"flag"
-	"github.com/francoispqt/gojay/gojay/codegen"
 	"log"
+
+	"github.com/francoispqt/gojay/gojay/codegen"
 )
 
 var pkg = flag.String("pkg", "", "the package name of the generated file")
@@ -12,6 +13,7 @@ var src = flag.String("s", "", "source dir or file (absolute or relative path)")
 var types = flag.String("t", "", "types to generate")
 var annotation = flag.String("a", "json", "annotation tag (default json)")
 var poolObjects = flag.String("p", "", "generate code to reuse objects using sync.Pool")
+var errOnUnknown = flag.String("e", "", "generate code to error on unknown fields")
 
 func main() {
 	flag.Parse()