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How to contribute to Roughly

VS Code Extension Setup

Section titled “VS Code Extension Setup”
  • Run cd editors/code && bun install. This installs all necessary npm modules
  • Press Ctrl+Shift+B in VS Code to start compiling the client in watch mode.
  • Switch to the Run and Debug View in the Sidebar (Ctrl+Shift+D).
  • Select Launch Client from the drop down (if it is not already).
  • Press ▷ to run the launch config (F5).
  • In the Extension Development Host instance of VSCode, open a document with a .R extension.

Words of warning

Section titled “Words of warning”

The launch.json contains a setting:

"autoAttachChildProcesses": true,

For me this led to the issue that the language server wasn’t spawned because I had CodeLLDB from nixpkgs installed.

Roadmap

Section titled “Roadmap”
  • static analysis
    • type checking
    • name binding
      • are all names defined
      • unused names (variables & parameters)
  • variable renaming
  • inlay hints

Formatting

Section titled “Formatting”

Comments in expressions

Section titled “Comments in expressions”

The main challenge in formatting code is handling comments because they can appear at any location. This is particualar hard to handle these expressions:

  • if expression
  • for expression
  • repeat statment
  • while expression
  • binary operator
  • extract operator

Example of if expressions

Section titled “Example of if expressions”

For example, in an if expression comments can appear at any location (numerated):

if
# 1
( # open
  # 2
  a && b # condition
  # 3
) # close
# 4
{
  y
}
# 5
else
# 6
{
  4
}

With a structured AST, we might typically could write our code in a concise functional style:

let condition = fmt(field("condition")?);
let consequence = fmt(field("consequence")?);
let alternative = fmt(field("alternative")?);
format!("if({condition}) {{ {consequence} }} else {{ {alternative} }}");

However, due to the arbitrary placement of comments, we must adopt a more imperative style. This approach preserves comments but somewhat harder to comprehend:

let mut out = String::new();
let mut cursor = node.walk();
if cursor.goto_first_child() {
  loop {
    match cursor.field_name() {
      None => match child.kind() {
        "if" => out.push_str("if"),
        "else" => ...,
        "comment" => ...,
        _ => unreachable!(),
      },
      Some(field_name) => match field_name {
        "open" => ...,
        "condition" => ...,
        "close" => ...,
        "consequence" | "alternative" => ...,
        _ => unreachable!(),
      },
    };


    if !cursor.goto_next_sibling() {
        cursor.goto_parent();
        break;
    }
  }
};
out

Tree-sitter: How to handle required fields

Section titled “Tree-sitter: How to handle required fields”
  • For formatting we do an initial check if there are no errors, so we can safely assume that all required fields are present
  • For type-checking we should do the same
  • For checks/diagnostics that run while typing (syntax & fast), we cannot make any assumption
  • Same is true for index. It should still be possible to index a file, while there are parse errors

tree-sitter-r vs R parser

Section titled “tree-sitter-r vs R parser”

No default for parameter

Section titled “No default for parameter”

Accept by tree-sitter-r but rejected by R.

function(parameter =) {}

See https://github.com/r-lib/tree-sitter-r/issues/161

line break after else

Section titled “line break after else”

This is valid R but cannot be parsed by tree-sitter-r

if (TRUE) {
  1
} else
{
  2
}

Two line breaks after extract_operator

Section titled “Two line breaks after extract_operator”

This is valid R but cannot be parsed by tree-sitter-r

foo$


bar

See https://github.com/r-lib/tree-sitter-r/issues/166

Linting ideas

Section titled “Linting ideas”
  • Empty loops: for, while, repeat
  • unused variables

References

Section titled “References”

R

Section titled “R”

VS Code Extensions

Section titled “VS Code Extensions”

Other Language Servers written in Rust

Section titled “Other Language Servers written in Rust”

Formatting

Section titled “Formatting”

Language Design / Typing

Section titled “Language Design / Typing”

Out of order issue

Section titled “Out of order issue”
Home Docs Formatter Linter Config

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Getting Started Formatter Linter Language Server Configuration

Contributing

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