Support loading comments

[Arianna2028]

Context We use this library to parse and modify Terraform files. We do this by reading a particular resource using this library, then using the data from that to write a new resource back to the file in the same place, removing the old one (using with_meta to know where it was). However, since no comments are output, we end up removing any that were present inside the original block.

Possible Enhancement If possible, it would be really helpful to optionally include parsed comments in the output from loads/load.

For example, if I parse a resource like this:

resource "aws_ec2_tag" "example" {
  # This is a comment
  resource_id = aws_vpn_connection.example.transit_gateway_attachment_id
  key         = "Name"
  value       = "Hello World"
}

I currently get the following dictionary representation:

{
    "resource": [
        {
            "aws_ec2_tag": {
                "example": {
                    "resource_id": "${aws_vpn_connection.example.transit_gateway_attachment_id}",
                    "key": "Name",
                    "value": "Hello World",
                    "__start_line__": 1,
                    "__end_line__": 6
                }
            }
        }
    ]
}

But maybe comment data could be added alongside it, something like:

{
    "resource": [
        {
            "aws_ec2_tag": {
                "example": {
                    "resource_id": "${aws_vpn_connection.example.transit_gateway_attachment_id}",
                    "key": "Name",
                    "value": "Hello World",
                    "__start_line__": 1,
                    "__end_line__": 6,
                    "__comments__": [
                        {
                            "__start_line__": 2,
                            "__end_line__": 2,
                            "text": "This is a comment"
                        }
                    ]
                }
            }
        }
    ]
}

[IButskhrikidze]

Seems would be helpful for some cases but requires making some keys reserved.

for instance, what if comments will be key itself?

[Arianna2028]

Yeah, I guess it would mean the __comments__ key would be reserved. Isn't this technically true for __start_line__ and __end_line__ already as well, though?

Alternatively, maybe __comments__ could be renamed to something with characters that are not considered valid in Terraform, so there is no possible conflict? I believe symbols are not considered valid syntax, so that might work.

[jaredhinzecs]

This would be a very useful feature for my Team. Currently, we have existing Terraform file structures we require people to duplicate and lightly modify select fields for various deployments. We use comments within these files to help segment logical blocks of code and provide context to readers. Presently, I have created a script to generate these file structures, but it wouldn't pass in a code review due to the comments being deleted. I'd love if this library allowed users to maintain the entire layout of whichever file is loaded which includes comments AND blank lines (which may not be commented). Formatting can be handled by other tooling imo. Though, maintaining overall format wouldn't be a bad idea either. I just wouldn't let that hold up the implementation of comment and blank line retention.