From: LE Manh Cuong <cuong.manhle.vn@gmail.com>
Date: Sat, 27 Oct 2018 18:44:09 +0000 (+0700)
Subject: encoding/json: add Path to UnmarshalTypeError
X-Git-Tag: go1.13beta1~1219
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=29bc4f12581d836a96139c924f16a4987324edd1;p=gostls13.git

encoding/json: add Path to UnmarshalTypeError

When parsing nested object, UnmarshalTypeError does not contain actual
path to nested field in original JSON.

This commit change Field to contain the full path to that field. One
can get the Field name by stripping all the leading path elements.

Fixes #22369

Change-Id: I6969cc08abe8387a351e3fb2944adfaa0dccad2a
Reviewed-on: https://go-review.googlesource.com/c/go/+/145218
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
---

diff --git a/src/encoding/json/decode.go b/src/encoding/json/decode.go
index 731553dca6..3900bcc165 100644
--- a/src/encoding/json/decode.go
+++ b/src/encoding/json/decode.go
@@ -125,7 +125,7 @@ type UnmarshalTypeError struct {
 	Type   reflect.Type // type of Go value it could not be assigned to
 	Offset int64        // error occurred after reading Offset bytes
 	Struct string       // name of the struct type containing the field
-	Field  string       // name of the field holding the Go value
+	Field  string       // the full path from root node to the field
 }
 
 func (e *UnmarshalTypeError) Error() string {
@@ -730,7 +730,11 @@ func (d *decodeState) object(v reflect.Value) error {
 					}
 					subv = subv.Field(i)
 				}
-				d.errorContext.Field = f.name
+				if originalErrorContext.Field == "" {
+					d.errorContext.Field = f.name
+				} else {
+					d.errorContext.Field = originalErrorContext.Field + "." + f.name
+				}
 				d.errorContext.Struct = t
 			} else if d.disallowUnknownFields {
 				d.saveError(fmt.Errorf("json: unknown field %q", key))
diff --git a/src/encoding/json/decode_test.go b/src/encoding/json/decode_test.go
index 60454c6058..d99d65d763 100644
--- a/src/encoding/json/decode_test.go
+++ b/src/encoding/json/decode_test.go
@@ -45,6 +45,14 @@ type W struct {
 	S SS
 }
 
+type P struct {
+	PP PP
+}
+
+type PP struct {
+	T T
+}
+
 type SS string
 
 func (*SS) UnmarshalJSON(data []byte) error {
@@ -816,7 +824,7 @@ var unmarshalTests = []unmarshalTest{
 		err: &UnmarshalTypeError{
 			Value:  "string",
 			Struct: "V",
-			Field:  "F2",
+			Field:  "V.F2",
 			Type:   reflect.TypeOf(int32(0)),
 			Offset: 20,
 		},
@@ -827,7 +835,7 @@ var unmarshalTests = []unmarshalTest{
 		err: &UnmarshalTypeError{
 			Value:  "string",
 			Struct: "V",
-			Field:  "F2",
+			Field:  "V.F2",
 			Type:   reflect.TypeOf(int32(0)),
 			Offset: 30,
 		},
@@ -923,6 +931,18 @@ var unmarshalTests = []unmarshalTest{
 		ptr: new(MustNotUnmarshalText),
 		err: &UnmarshalTypeError{Value: "object", Type: reflect.TypeOf(&MustNotUnmarshalText{}), Offset: 1},
 	},
+	// #22369
+	{
+		in:  `{"PP": {"T": {"Y": "bad-type"}}}`,
+		ptr: new(P),
+		err: &UnmarshalTypeError{
+			Value:  "string",
+			Struct: "T",
+			Field:  "PP.T.Y",
+			Type:   reflect.TypeOf(int(0)),
+			Offset: 29,
+		},
+	},
 }
 
 func TestMarshal(t *testing.T) {