rubocopfmt.el

Emacs minor-mode to format Ruby code with RuboCop on save via it's --auto-correct option.

Installation

Drop rubocopfmt.el somewhere into you load-path and require it. Personally I favour the folder ~/.emacs.d/vendor:

(add-to-list 'load-path "~/.emacs.d/vendor")
(require 'rubocopfmt)

Usage

To enable formatting ruby-mode buffers on save, simply enable rubocopfmt-mode with something like this in your config:

(add-hook 'ruby-mode-hook #'rubocopfmt-mode)

Commands

rubocopfmt - Format current buffer with RuboCop.
rubocopfmt-mode - Toggle formatting on save on/off.

Internals

rubocopfmt works by executing rubocop against the file you are saving. To ensure RuboCop behaves as expected, it is executed from within the same directory as the file you are saving.

Bundler Integration

If a Gemfile is found in the current directory or in any parent directory, bundle exec rubocop [...] will be used to execute RuboCop. This does mean that projects with a Gemfile are required to have rubocop listed as a dependency for rubocopfmt to work.

This ensures that formatting is done with the same version of RuboCop that the project lists as a dependency.

Disabled Cops

There's a few of cops in RuboCop that can cause confusion and annoyance when run against work-in-progress code. Hence rubocopfmt disables the worst offenders by default. You can configure which cops are disabled by customizing the rubocopfmt-disabled-cops variable.

Cops disabled by default:

Lint/Debugger: Removes debugger statements. Not helpful when you need to debug something.
Lint/UnusedBlockArgument: Don't prefix unused block argument variable names with _. This cop causes issues if you save after defining a block, but before you use all arguments of the block.
Lint/UnusedMethodArgument: Don't prefix unused method argument variable names with _. This cop causes issues if you save after defining a method, but before you use all arguments of the method.
Style/EmptyMethod: Don't remove remove empty line for empty methods. This cop is annoying if you save right after defining a new method.

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