Merge pull request #7 from bboreham/fewer-panics

On panic while printing, attempt to print panic value

Author: ChrisHines

encode.go

@@ -278,7 +278,7 @@ func safeError(err error) (s string, ok bool) {
 if v := reflect.ValueOf(err); v.Kind() == reflect.Ptr && v.IsNil() {
 s, ok = "null", false
 } else {
-panic(panicVal)
+s, ok = fmt.Sprintf("PANIC:%v", panicVal), false
 }
 }
 }()
@@ -292,7 +292,7 @@ func safeString(str fmt.Stringer) (s string, ok bool) {
 if v := reflect.ValueOf(str); v.Kind() == reflect.Ptr && v.IsNil() {
 s, ok = "null", false
 } else {
-panic(panicVal)
+s, ok = fmt.Sprintf("PANIC:%v", panicVal), true
 }
 }
 }()
@@ -306,7 +306,7 @@ func safeMarshal(tm encoding.TextMarshaler) (b []byte, err error) {
 if v := reflect.ValueOf(tm); v.Kind() == reflect.Ptr && v.IsNil() {
 b, err = nil, nil
 } else {
-panic(panicVal)
+b, err = nil, fmt.Errorf("panic when marshalling: %s", panicVal)
 }
 }
 }()

encode_test.go

@@ -125,6 +125,10 @@ func TestMarshalKeyvals(t *testing.T) {
 {in: kv(decimalStringer{5, 9}, "v"), want: []byte("5.9=v")},
 {in: kv((*decimalStringer)(nil), "v"), err: logfmt.ErrNilKey},
 {in: kv(marshalerStringer{5, 9}, "v"), want: []byte("5.9=v")},
+{in: kv("k", panicingStringer{0}), want: []byte("k=ok")},
+{in: kv("k", panicingStringer{1}), want: []byte("k=PANIC:panic1")},
+// Need extra mechanism to test panic-while-printing-panicVal
+//{in: kv("k", panicingStringer{2}), want: []byte("?")},
 }
 
 for _, d := range data {
@@ -196,6 +200,20 @@ func (errorMarshaler) MarshalText() ([]byte, error) {
 return nil, errMarshal
 }
 
+type panicingStringer struct {
+a int
+}
+
+func (p panicingStringer) String() string {
+switch p.a {
+case 1:
+panic("panic1")
+case 2:
+panic(panicingStringer{a: 2})
+}
+return "ok"
+}
+
 func BenchmarkEncodeKeyval(b *testing.B) {
 b.ReportAllocs()
 enc := logfmt.NewEncoder(ioutil.Discard)