gojson: added MarshalSafeCollections

gojson/encode.go

@@ -167,6 +167,17 @@ func Marshal(v any) ([]byte, error) {
 	return buf, nil
 }
 
+// MarshalSafeCollections is like Marshal except it will marshal nil maps and
+// slices as '{}' and '[]' respectfully instead of 'null'
+func MarshalSafeCollections(v interface{}, nilSafeSlices bool, nilSafeMaps bool) ([]byte, error) {
+	e := &encodeState{}
+	err := e.marshal(v, encOpts{escapeHTML: true, nilSafeSlices: nilSafeSlices, nilSafeMaps: nilSafeMaps})
+	if err != nil {
+		return nil, err
+	}
+	return e.Bytes(), nil
+}
+
 // MarshalIndent is like Marshal but applies Indent to format the output.
 // Each JSON element in the output will begin on a new line beginning with prefix
 // followed by one or more copies of indent according to the indentation nesting.
@@ -363,6 +374,10 @@ type encOpts struct {
 	quoted bool
 	// escapeHTML causes '<', '>', and '&' to be escaped in JSON strings.
 	escapeHTML bool
+	// nilSafeSlices marshals a nil slices into '[]' instead of 'null'
+	nilSafeSlices bool
+	// nilSafeMaps marshals a nil maps '{}' instead of 'null'
+	nilSafeMaps bool
 }
 
 type encoderFunc func(e *encodeState, v reflect.Value, opts encOpts)
@@ -776,7 +791,11 @@ type mapEncoder struct {
 
 func (me mapEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
 	if v.IsNil() {
-		e.WriteString("null")
+		if opts.nilSafeMaps {
+			e.WriteString("{}")
+		} else {
+			e.WriteString("null")
+		}
 		return
 	}
 	if e.ptrLevel++; e.ptrLevel > startDetectingCyclesAfter {
@@ -829,9 +848,13 @@ func newMapEncoder(t reflect.Type) encoderFunc {
 	return me.encode
 }
 
-func encodeByteSlice(e *encodeState, v reflect.Value, _ encOpts) {
+func encodeByteSlice(e *encodeState, v reflect.Value, opts encOpts) {
 	if v.IsNil() {
-		e.WriteString("null")
+		if opts.nilSafeSlices {
+			e.WriteString(`""`)
+		} else {
+			e.WriteString("null")
+		}
 		return
 	}
 	s := v.Bytes()
@@ -866,7 +889,11 @@ type sliceEncoder struct {
 
 func (se sliceEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
 	if v.IsNil() {
-		e.WriteString("null")
+		if opts.nilSafeSlices {
+			e.WriteString("[]")
+		} else {
+			e.WriteString("null")
+		}
 		return
 	}
 	if e.ptrLevel++; e.ptrLevel > startDetectingCyclesAfter {