diff --git a/doc/next/6-stdlib/99-minor/encoding/json/68941.md b/doc/next/6-stdlib/99-minor/encoding/json/68941.md new file mode 100644 index 00000000000..c7abec8b7fd --- /dev/null +++ b/doc/next/6-stdlib/99-minor/encoding/json/68941.md @@ -0,0 +1 @@ +[UnmarshalTypeError.Field] now includes embedded structs to provide more detailed error messages. diff --git a/src/encoding/json/decode.go b/src/encoding/json/decode.go index 19d4563e33f..1a05ef59a2c 100644 --- a/src/encoding/json/decode.go +++ b/src/encoding/json/decode.go @@ -127,7 +127,7 @@ 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 // the full path from root node to the field + Field string // the full path from root node to the field, include embedded struct } func (e *UnmarshalTypeError) Error() string { @@ -701,7 +701,10 @@ func (d *decodeState) object(v reflect.Value) error { if f != nil { subv = v destring = f.quoted - for _, i := range f.index { + if d.errorContext == nil { + d.errorContext = new(errorContext) + } + for i, ind := range f.index { if subv.Kind() == reflect.Pointer { if subv.IsNil() { // If a struct embeds a pointer to an unexported type, @@ -721,13 +724,16 @@ func (d *decodeState) object(v reflect.Value) error { } subv = subv.Elem() } - subv = subv.Field(i) + if i < len(f.index)-1 { + d.errorContext.FieldStack = append( + d.errorContext.FieldStack, + subv.Type().Field(ind).Name, + ) + } + subv = subv.Field(ind) } - if d.errorContext == nil { - d.errorContext = new(errorContext) - } - d.errorContext.FieldStack = append(d.errorContext.FieldStack, f.name) d.errorContext.Struct = t + d.errorContext.FieldStack = append(d.errorContext.FieldStack, f.name) } 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 752825cffea..71895a9bb14 100644 --- a/src/encoding/json/decode_test.go +++ b/src/encoding/json/decode_test.go @@ -898,6 +898,19 @@ var unmarshalTests = []struct { }, }, + { + CaseName: Name(""), + in: `{"Level1a": "hello"}`, + ptr: new(Top), + err: &UnmarshalTypeError{ + Value: "string", + Struct: "Top", + Field: "Embed0a.Level1a", + Type: reflect.TypeFor[int](), + Offset: 10, + }, + }, + // issue 15146. // invalid inputs in wrongStringTests below. {CaseName: Name(""), in: `{"B":"true"}`, ptr: new(B), out: B{true}, golden: true},