encoding/json: encode nil encoding.TextMarshaler instance as "null"
Fixes #34235.
Change-Id: Ia3795fd18860530fa6a4b171545f525e784ffdcb
GitHub-Last-Rev: 1a319c452857818f7aaf22ef46823b43ca9b2276
GitHub-Pull-Request: golang/go#34238
Reviewed-on: https://go-review.googlesource.com/c/go/+/194642
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/encode.go b/src/encoding/json/encode.go
index 0758b2f..e5dd1b7 100644
--- a/src/encoding/json/encode.go
+++ b/src/encoding/json/encode.go
@@ -481,7 +481,11 @@
e.WriteString("null")
return
}
- m := v.Interface().(encoding.TextMarshaler)
+ m, ok := v.Interface().(encoding.TextMarshaler)
+ if !ok {
+ e.WriteString("null")
+ return
+ }
b, err := m.MarshalText()
if err != nil {
e.error(&MarshalerError{v.Type(), err})
diff --git a/src/encoding/json/encode_test.go b/src/encoding/json/encode_test.go
index daab713..18a92ba 100644
--- a/src/encoding/json/encode_test.go
+++ b/src/encoding/json/encode_test.go
@@ -6,6 +6,7 @@
import (
"bytes"
+ "encoding"
"fmt"
"log"
"math"
@@ -453,18 +454,31 @@
BugB
}
-// Issue 16042. Even if a nil interface value is passed in
-// as long as it implements MarshalJSON, it should be marshaled.
-type nilMarshaler string
+// golang.org/issue/16042.
+// Even if a nil interface value is passed in, as long as
+// it implements Marshaler, it should be marshaled.
+type nilJSONMarshaler string
-func (nm *nilMarshaler) MarshalJSON() ([]byte, error) {
+func (nm *nilJSONMarshaler) MarshalJSON() ([]byte, error) {
if nm == nil {
return Marshal("0zenil0")
}
return Marshal("zenil:" + string(*nm))
}
-// Issue 16042.
+// golang.org/issue/34235.
+// Even if a nil interface value is passed in, as long as
+// it implements encoding.TextMarshaler, it should be marshaled.
+type nilTextMarshaler string
+
+func (nm *nilTextMarshaler) MarshalText() ([]byte, error) {
+ if nm == nil {
+ return []byte("0zenil0"), nil
+ }
+ return []byte("zenil:" + string(*nm)), nil
+}
+
+// See golang.org/issue/16042 and golang.org/issue/34235.
func TestNilMarshal(t *testing.T) {
testCases := []struct {
v interface{}
@@ -478,8 +492,11 @@
{v: []byte(nil), want: `null`},
{v: struct{ M string }{"gopher"}, want: `{"M":"gopher"}`},
{v: struct{ M Marshaler }{}, want: `{"M":null}`},
- {v: struct{ M Marshaler }{(*nilMarshaler)(nil)}, want: `{"M":"0zenil0"}`},
- {v: struct{ M interface{} }{(*nilMarshaler)(nil)}, want: `{"M":null}`},
+ {v: struct{ M Marshaler }{(*nilJSONMarshaler)(nil)}, want: `{"M":"0zenil0"}`},
+ {v: struct{ M interface{} }{(*nilJSONMarshaler)(nil)}, want: `{"M":null}`},
+ {v: struct{ M encoding.TextMarshaler }{}, want: `{"M":null}`},
+ {v: struct{ M encoding.TextMarshaler }{(*nilTextMarshaler)(nil)}, want: `{"M":"0zenil0"}`},
+ {v: struct{ M interface{} }{(*nilTextMarshaler)(nil)}, want: `{"M":null}`},
}
for _, tt := range testCases {
