json: use panic/recover to handle errors in Marshal

R=r, gri
CC=golang-dev
https://golang.org/cl/872041

diff --git a/src/pkg/json/struct.go b/src/pkg/json/struct.go
index 46f04146d6341cd09191d877f024080987a2e072..b89ef29a8e6c505c6a0d44061a3b251cb81a994b 100644 (file)
--- a/src/pkg/json/struct.go
+++ b/src/pkg/json/struct.go
@@ -346,29 +346,24 @@ func (s *writeState) writeIndent() {
        }
 }
 
-func (s *writeState) writeArrayOrSlice(val reflect.ArrayOrSliceValue) (err os.Error) {
+func (s *writeState) writeArrayOrSlice(val reflect.ArrayOrSliceValue) {
        s.descend('[')
 
        for i := 0; i < val.Len(); i++ {
                s.writeIndent()
-
-               if err = s.writeValue(val.Elem(i)); err != nil {
-                       return
-               }
-
+               s.writeValue(val.Elem(i))
                if i < val.Len()-1 {
                        s.WriteByte(',')
                }
        }
 
        s.ascend(']')
-       return
 }
 
-func (s *writeState) writeMap(val *reflect.MapValue) (err os.Error) {
+func (s *writeState) writeMap(val *reflect.MapValue) {
        key := val.Type().(*reflect.MapType).Key()
        if _, ok := key.(*reflect.StringType); !ok {
-               return &MarshalError{val.Type()}
+               panic(&MarshalError{val.Type()})
        }
 
        s.descend('{')
@@ -376,45 +371,34 @@ func (s *writeState) writeMap(val *reflect.MapValue) (err os.Error) {
        keys := val.Keys()
        for i := 0; i < len(keys); i++ {
                s.writeIndent()
-
                fmt.Fprintf(s, "%s:", Quote(keys[i].(*reflect.StringValue).Get()))
-
-               if err = s.writeValue(val.Elem(keys[i])); err != nil {
-                       return
-               }
-
+               s.writeValue(val.Elem(keys[i]))
                if i < len(keys)-1 {
                        s.WriteByte(',')
                }
        }
 
        s.ascend('}')
-       return
 }
 
-func (s *writeState) writeStruct(val *reflect.StructValue) (err os.Error) {
+func (s *writeState) writeStruct(val *reflect.StructValue) {
        s.descend('{')
 
        typ := val.Type().(*reflect.StructType)
 
        for i := 0; i < val.NumField(); i++ {
                s.writeIndent()
-
-               fieldValue := val.Field(i)
                fmt.Fprintf(s, "%s:", Quote(typ.Field(i).Name))
-               if err = s.writeValue(fieldValue); err != nil {
-                       return
-               }
+               s.writeValue(val.Field(i))
                if i < val.NumField()-1 {
                        s.WriteByte(',')
                }
        }
 
        s.ascend('}')
-       return
 }
 
-func (s *writeState) writeValue(val reflect.Value) (err os.Error) {
+func (s *writeState) writeValue(val reflect.Value) {
        if val == nil {
                fmt.Fprint(s, "null")
                return
@@ -424,28 +408,28 @@ func (s *writeState) writeValue(val reflect.Value) (err os.Error) {
        case *reflect.StringValue:
                fmt.Fprint(s, Quote(v.Get()))
        case *reflect.ArrayValue:
-               err = s.writeArrayOrSlice(v)
+               s.writeArrayOrSlice(v)
        case *reflect.SliceValue:
-               err = s.writeArrayOrSlice(v)
+               s.writeArrayOrSlice(v)
        case *reflect.MapValue:
-               err = s.writeMap(v)
+               s.writeMap(v)
        case *reflect.StructValue:
-               err = s.writeStruct(v)
+               s.writeStruct(v)
        case *reflect.ChanValue,
                *reflect.UnsafePointerValue,
                *reflect.FuncValue:
-               err = &MarshalError{val.Type()}
+               panic(&MarshalError{val.Type()})
        case *reflect.InterfaceValue:
                if v.IsNil() {
                        fmt.Fprint(s, "null")
                } else {
-                       err = s.writeValue(v.Elem())
+                       s.writeValue(v.Elem())
                }
        case *reflect.PtrValue:
                if v.IsNil() {
                        fmt.Fprint(s, "null")
                } else {
-                       err = s.writeValue(v.Elem())
+                       s.writeValue(v.Elem())
                }
        case *reflect.UintptrValue:
                fmt.Fprintf(s, "%d", v.Get())
@@ -461,14 +445,15 @@ func (s *writeState) writeValue(val reflect.Value) (err os.Error) {
                value := val.(reflect.Value)
                fmt.Fprintf(s, "%#v", value.Interface())
        }
-       return
 }
 
 func (s *writeState) marshal(w io.Writer, val interface{}) (err os.Error) {
-       err = s.writeValue(reflect.NewValue(val))
-       if err != nil {
-               return
-       }
+       defer func() {
+               if e := recover(); e != nil {
+                       err = e.(*MarshalError)
+               }
+       }()
+       s.writeValue(reflect.NewValue(val))
        if s.newlines {
                s.WriteByte('\n')
        }