hclwrite: Rewrite comments on blocks and attributes

[izeau]

Greetings,

The goal of this PR is to start a discussion around the manipulation of leadComments / lineComments in attributes and leadComments in blocks (I could not find a real reason for them to have lineComments, to be honest). This would solve the use case presented in #459, for line-style comments at least — since block-style comments seem to only be parsed as leadComments if they are on the same line as the attribute / block they annotate.

This PR adds a few methods to hclwrite.Block and hclwrite.Body. I’m quite new to Go so I’m sure my code may be clunky or non-idiomatic; feedback is welcome!

Example

func main() {
	file, _ := hclwrite.ParseConfig([]byte(`
city "tokyo" {
	# Tokyo is the capital of Japan
	country   = country.japan
	time_zone = "UTC+09:00"
	language  = "japanese" # jp-jp

}`,
	), "", hcl.InitialPos)

	tokyo := file.Body().FirstMatchingBlock("city", []string{"tokyo"})
	tokyo.SetComment("# Pop: 14M\n")
	tokyo.Body().SetAttributeLeadComments("country", nil)
	tokyo.Body().SetAttributeLeadComment("time_zone", "# Japan Standard Time\n")
	tokyo.Body().SetAttributeLineComments("language", nil)

	file.WriteTo(os.Stdout)
}

Output

# Pop: 14M
city "tokyo" {
  country = country.japan
  # Japan Standard Time
  time_zone = "UTC+09:00"
  language  = "japanese"
}

Caveats

As you can see on this example, I had to insert a newline after the language attribute, as the parser would otherwise create no TokenNewline: it is absorbed by the line comment. This is specific to line-style comments and would maybe be solved by rearranging the parser so that parsing line-style comments generates a TokenComment without a final newline char as well as a separate TokenNewline, if that makes sense. That may qualify as a breaking change however.

[izeau]

Is there anything I can do to have this merged somehow?