Preserve comments on source file

[mohsenari]

I was wondering if there is a way to Unmarshal hjson to a go struct but preserve arbitrary comments on the source json. For example if my hjson looks like this:

{
// random comment
  "foo": "bar",
  "foo2": "bar2"
}

I want to preserve a comment on a random line in the json, unmarshal the file to a go struct, change bar to bar-modified.
Then marshal and save to file.

Is it possible to preserve comments when you don't know which line might have a comment on it?

[trobro]

I don't know of any solution for structs, because the tags on structs are declared in the struct declaration and cannot be altered after that.

One solution I could do is to create a special hjson.Value interface in hjson-go similar to the Value class in hjson-cpp. So that Hjson can be unmarshalled into a tree of hjson.Value objects where comments can be read and written on each object.

[mohsenari]

Yeah I think that could work. To be clear my goal is not to read & write comments even though it would be a nice feature to have. My goal is to preserve comments, and change the key-value data. Then save my changed data back to json while keeping the comments unchanged.

[trobro]

In the new release v4.3.0 you can read-change-write with preserved comments and whitespace for example like this:

var node hjson.Node
if err := hjson.Unmarshal(txt, &node); err != nil {
  panic(err)
}
if _, _, err := node.SetKey("myKey", "myValue"); err != nil {
  panic(err)
}
outBytes, err := hjson.Marshal(node)
if err != nil {
  panic(err)
}