Fix Ruby LSP formatting range to comply with LSP specification

[vitallium]

Motivation

Hi! While working on the Ruby LSP extension for the IntelliJ platform, I noticed an issue (or not?) with the formatting response from the Ruby Language Server. Thanks!

Implementation

The current implementation of formatting
does not use the proper range for a response.
Consider the following Ruby code:

class A
  def my_method
   [1]
  end
end

Let's pretend that our RuboCop configuration specifies omitting whitespaces inside array declarations, which means the code above is not properly formatted.
The code should be formatted like this:

class A
  def my_method
   [ 1 ]
  end
end

When a client asks Ruby LSP to format the first code, the server sends a response (taken from the Zed editor) where the reported end property of the Range interface has line and character keys that do not match the source document.
Both of them equal the character size of the document.

{
   "id":6,
   "result":[
      {
         "range":{
            "start":{
               "line":0,
               "character":0
            },
            "end":{
               "line":43,
               "character":43
            }
         },
         "newText":"class A\n  def my_method\n    [ 1 ]\n  end\nend\n"
      }
   ],
   "jsonrpc":"2.0"
}

For some reason, Visual Studio Code considers this response valid, and the code is formatted properly.
However, some editors perform a check to ensure that the reported response from Ruby LSP is not out of bounds of the current text document.
According to the LSP specification from the link below: https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#range A range in a text document expressed as (zero-based) start and end positions. The correct response should be:

{
   "id":35,
   "result":[
      {
         "range":{
            "start":{
               "line":0,
               "character":0
            },
            "end":{
               "line":5,
               "character":0
            }
         },
         "newText":"class A\n  def my_method\n    [ 1 ]\n  end\nend\n"
      }
   ],
   "jsonrpc":"2.0"
}

Automated Tests

I am happy to add unit tests for that, but I am not sure where I should start. I didn't find any tests regarding testing requests/responses in accordance with LSP specs.

Manual Tests

Unfortunately, there is no way to test this in Visual Studio Code because formatting, for some reason, works just fine there.

[vinistock]

Thank you for the contribution!

[vitallium]

@vinistock thanks a lot for finishing it! I’ve been a bit slow recently in updating my contributions.