Handle add with path="". Fixes #188

Author: evanphx

v5/patch.go

@@ -729,6 +729,32 @@ func (p Patch) add(doc *container, op Operation, options *ApplyOptions) error {
 return errors.Wrapf(ErrMissing, "add operation failed to decode path")
 }
 
+// special case, adding to empty means replacing the container with the value given
+if path == "" {
+val := op.value()
+
+var pd container
+if (*val.raw)[0] == '[' {
+pd = &partialArray{
+self: val,
+}
+} else {
+pd = &partialDoc{
+self: val,
+}
+}
+
+err := json.Unmarshal(*val.raw, pd)
+
+if err != nil {
+return err
+}
+
+*doc = pd
+
+return nil
+}
+
 if options.EnsurePathExistsOnAdd {
 err = ensurePathExists(doc, path, options)
 

v5/patch_test.go

@@ -592,6 +592,20 @@ var Cases = []Case{
 false,
 false,
 },
+{
+`{}`,
+`[{"op":"add","path":"","value":{"foo":"bar"}}]`,
+`{"foo": "bar"}`,
+false,
+false,
+},
+{
+`[]`,
+`[{"op":"add","path":"","value":{"foo":"bar"}}, {"op": "add", "path": "/qux", "value": 1}]`,
+`{"foo": "bar", "qux": 1}`,
+false,
+false,
+},
 }
 
 type BadCase struct {