Ruby Formatter & Indenter

What this Ruby formatter does

This Ruby formatter is a keyword-aware re-indenter. It reads your code line by line, tracks where blocks open and close (class, module, def, if, unless, case, while, begin, do, brackets) and where they end, and re-indents every line accordingly. It is the fix you need when code pasted from a chat, an email or a PDF has lost its indentation, or when tabs and spaces were mixed.

To be clear about its scope: it changes indentation only. Spacing inside a line, such as @items=items, stays as written, and it does not rewrite syntax the way RuboCop's autocorrect or the Standard gem do.

Example

module Billing
class Invoice
attr_reader :items
def initialize(items=[])
@items=items
end
def total
items.sum { |i| i[:price]*i[:qty] }
end
def status
case total
when 0 then :empty
else
:open
end
end
end
end

module Billing
  class Invoice
    attr_reader :items
    def initialize(items=[])
      @items=items
    end
    def total
      items.sum { |i| i[:price]*i[:qty] }
    end
    def status
      case total
      when 0 then :empty
      else
        :open
      end
    end
  end
end

Nested module and class bodies, methods, and the case expression are indented two spaces per level. when and else line up with case, which is the layout recommended by the community Ruby Style Guide.

Ruby constructs it understands

• Block keywords: class, module, def, if, unless, while, until, for, case, begin and do, each closed by end.
• Mid-block keywords: else, elsif, when, in, rescue and ensure are out-dented to the level of their opening keyword.
• Modifier forms like return if empty? do not open a block, because the keyword is not at the start of the line.
• Assigned conditionals like label = if paid then "Paid" else "Due" end spread over lines are indented correctly.
• Endless methods (def full_name = "#{first} #{last}") do not open a block.
• Brace blocks and literals: { |x| ... }, multi-line arrays and hashes indent by bracket depth.
• Heredocs and =begin/=end comments are copied verbatim, since their contents are data.

Ruby style basics

The community Ruby Style Guide, which RuboCop enforces, sets conventions worth following alongside correct indentation:

• Two spaces per level, never tabs.
• snake_case for methods and variables, CamelCase for classes and modules, SCREAMING_SNAKE_CASE for constants.
• Spaces around operators and after commas: @items = items, i[:price] * i[:qty].
• Prefer { } for single-line blocks and do ... end for multi-line blocks.

For automatic enforcement of those rules in a project, run rubocop -a or standardrb --fix locally; this page gives you fast, dependency-free indentation in the browser.

Finding a missing end

Ruby's "unexpected end-of-input" error means some block was never closed. Paste the file here and look at the last line: if end is still indented instead of flush left, a block above it is missing its end. Scan upward for the first place where the indentation looks deeper than you intended. Too many end keywords show up the other way, as lines stuck at the left margin too early.

For Ruby data classes from JSON, try JSON to Ruby. Formatting ERB templates? The HTML parts are handled better by the HTML Formatter. All processing happens in your browser.