feat(json): add option to write json in multiline mode

[DmitriyLewen]

Description

json.Write() function writes JSON in 1 line.

It is not always convenient for human processing.
It would be cool to be able to save in a human-readable format (multi-line format)

[kzantow]

Instead of having a second method for this, we might want to introduce a simple options interface so a user can configure this option as well as others (escaping HTML, for example). This would mean we would have to update the Write function. It would look something like (completely untested):

// Write takes an SPDX Document and an io.Writer, and writes the document to the writer in JSON format.
func Write(doc common.AnyDocument, w io.Writer, opts ...WriteOption) error {
	e := json.NewEncoder(w)
	for _, opt := range opts {
		opt(e)
	}
	return e.Encode(doc)
}

type WriteOption func(*json.Encoder)

func Indent(indent string) WriteOption {
	return func(e *json.Encoder) {
		e.SetIndent("", indent)
	}
}

func EscapeHTML(escape bool) WriteOption {
	return func(e *json.Encoder) {
		e.SetEscapeHTML(escape)
	}
}

... and you would call the Write function like:

json.Write(doc, writer, json.Indent("  "))

... or if you also wanted to also prevent HTML escaping (which only partially works, unfortunately; won't expand on why here):

json.Write(doc, writer, json.Indent("  "), json.EscapeHTML(false))

What would you think about this approach?

On a side-note, you can just call json.MarshalIndent(doc, "", " ") directly in your code for this, but agree it would be nice to have this library provide some of the formatting options.

[DmitriyLewen]

@kzantow Thanks for faster response!

I thought about this way, but i was not sure if you wanted to add arguments to Write() function, so that the other Write() functions ( i mean yaml, json, etc...) have same format.

What would you think about this approach?

I think your solution is better. Tell me if this solution works for you - I'll update this PR.

[kzantow]

Since adding options as var args allows users to continue to use the same signature they already have been: json.Write(doc, writer), I think this stays consistent with the other Write functions. If you wanted to add analogous options for yaml.Write, I wouldn't be opposed to that, but I don't think it's necessary.

[lumjjb]

+1 on adding vargs which wouldn't change the interface, that would work nicely!

[DmitriyLewen]

Added changes in 755da28

[kzantow]

LGTM -- thanks for the contribution @DmitriyLewen 👍