Alternative R linters

lintr configuration.md

A portable configuration for the ‘lintr’ R package that includes a handful of custom linters that I commonly use.

arrow_assignment_linter.r

arrow_assignment_linter = function () {
  xpath = '//LEFT_ASSIGN[text() != ":="] | //RIGHT_ASSIGN'
  lint_message_fmt = 'Use =, not %s, for assignment.'

  lintr::Linter(\(source_expression) {
    if (! lintr::is_lint_level(source_expression, 'expression')) {
      return(list())
    }

    xml = source_expression$xml_parsed_content
    bad_expr = xml2::xml_find_all(xml, xpath)

    if (length(bad_expr) == 0L) {
      return(list())
    }

    operator = xml2::xml_text(bad_expr)

    lint_message = sprintf(lint_message_fmt, operator)
    lintr::xml_nodes_to_lints(bad_expr, source_expression, lint_message, type = 'style')
  })
}

config

linters: {
    config_dir = dirname(file)
    lapply(dir(config_dir, '\\.[rR]$', full.names = TRUE), source, local = environment())
    lintr::linters_with_defaults(
      assignment_linter = arrow_assignment_linter(),
      function_left_parentheses_linter = function_definition_linter(),
      line_length_linter = line_length_linter(120L),
      object_usage_linter = NULL, # unusably buggy
      quotes_linter = lintr::quotes_linter("'")
    )
  }

function_definition_linter.r

function_definition_linter = function () {
  bad_line_fun_xpath = '(//FUNCTION | //OP-LAMBDA)[@line1 != following-sibling::OP-LEFT-PAREN/@line1]'
  bad_line_call_xpath = '//SYMBOL_FUNCTION_CALL[@line1 != parent::expr/following-sibling::OP-LEFT-PAREN/@line1]'
  bad_col_fun_xpath = '//FUNCTION[
    @line1 = following-sibling::OP-LEFT-PAREN/@line1
    and @col2 != following-sibling::OP-LEFT-PAREN/@col1 - 2
  ]'
  bad_col_call_xpath = '//SYMBOL_FUNCTION_CALL[
    line1 = parent::expr/following-sibling::OP-LEFT-PAREN/@line1
    and @col2 != parent::expr/following-sibling::OP-LEFT-PAREN/@col1 - 1
  ]'

  lintr::Linter(\(source_expression) {
    if (! lintr::is_lint_level(source_expression, 'expression')) {
      return(list())
    }

    xml = source_expression$xml_parsed_content

    bad_line_fun_exprs = xml2::xml_find_all(xml, bad_line_fun_xpath)
    bad_line_fun_lints = lintr::xml_nodes_to_lints(
      bad_line_fun_exprs,
      source_expression = source_expression,
      lint_message = 'Left parenthesis should be on the same line as the \'function\' symbol.'
    )

    bad_line_call_exprs = xml2::xml_find_all(xml, bad_line_call_xpath)
    bad_line_call_lints = lintr::xml_nodes_to_lints(
      bad_line_call_exprs,
      source_expression = source_expression,
      lint_message = 'Left parenthesis should be on the same line as the function\'s symbol.'
    )

    bad_col_fun_exprs = xml2::xml_find_all(xml, bad_col_fun_xpath)
    bad_col_fun_lints = lintr::xml_nodes_to_lints(
      bad_col_fun_exprs,
      source_expression = source_expression,
      lint_message = 'Add spaces before the left parenthesis in a function definition.',
      range_start_xpath = 'number(./@col2 + 1)',
      range_end_xpath = 'number(./following-sibling::OP-LEFT-PAREN/@col1)'
    )

    bad_col_call_exprs = xml2::xml_find_all(xml, bad_col_call_xpath)
    bad_col_call_lints = lintr::xml_nodes_to_lints(
      bad_col_call_exprs,
      source_expression = source_expression,
      lint_message = 'Remove spaces before the left parenthesis in a function call.',
      range_start_xpath = 'number(./@col2 + 1)',
      range_end_xpath = 'number(./parent::expr/following-sibling::OP-LEFT-PAREN/@col1 - 1)'
    )

    c(bad_line_fun_lints, bad_line_call_lints, bad_col_fun_lints, bad_col_call_lints)
  })
}

line_length_linter.r

line_length_linter = function (length = 120L) {
  general_msg = paste('Lines should not be more than', length, 'characters.')

  lintr::Linter(\(source_expression) {
    if (! lintr::is_lint_level(source_expression, 'file')) {
      return(list())
    }

    # Note that this will handle “comment-looking” lines in multi-line strings incorrectly. But that’s fine.
    comment_lines = grep('^\\s*#', source_expression$file_lines)
    line_lengths = nchar(source_expression$file_lines)
    long_lines = setdiff(which(line_lengths > length), comment_lines)

    Map(
      \(long_line, line_length) {
        lintr::Lint(
          filename = source_expression$filename,
          line_number = long_line,
          column_number = length + 1L,
          type = 'style',
          message = paste(general_msg, 'This line is', line_length, 'characters.'),
          line = source_expression$file_lines[long_line],
          ranges = list(c(1L, line_length))
        )
      },
      long_lines,
      line_lengths[long_lines]
    )
  })
}