88 lines
2.9 KiB
Markdown
88 lines
2.9 KiB
Markdown
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---
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title: Rubocop
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---
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[Rubocop](https://github.com/bbatsov/rubocop) is a static analyis tool for
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[Ruby](https://www.ruby-lang.org/en/). What does this mean? It means Rubocop
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will to 'read' your code (as opposed to running it, hence the 'static' part
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of the name), and analyse it. The analysis rules Rubocop uses are from the
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[Ruby community style guide](https://github.com/bbatsov/ruby-style-guide).
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The style guide is a set of specific suggestions about how to write code which
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is more readable, more expressive, and more conventional. As a community, it
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would be terrific if we could read anyone else's code easily, and they could
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read ours easily. This is what Rubocop helps us to do. This sort of tool is
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always valuable, but it's particularly useful when you're learning Ruby, and
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you may code which is _correct_, but which doesn't stick to Ruby conventions,
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or doesn't take advantage of some of Ruby's more powerful features.
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Most usefully, Rubocop can automatically fix many of the minor warnings - like
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incorrect spacing. This is very helpful before code review as it means your
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fellow developers can focus on higher level concerns, and not have to waste
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time on syntax issues.
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## Using Rubocop
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### Installation
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Rubocop is delivered as a Gem, so on a typical project which uses Bundler you
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would add it to the development section of your `Gemfile`:
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```
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group :development do
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gem rubocop
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end
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```
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This means anyone using your project will have the same version of Rubocop, and
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everyone will agree on what the current best practice is.
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### Usage
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Before every commit, I like to check that my newly modified code complies with
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the commmunity standard, simply by running:
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```
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rubocop
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```
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This will output a list of warnings about your code.
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It can be helpful to ask Rubocop for more help:
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```
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rubocop --extra-details --display-cop-names
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```
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(You might add these to a `.rubocop` file to make them default.)
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Many editors will allow you to integrate Rubocop, which can give immediate
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feedback when you're writing code.
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### Fixing issues
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Let's say I've written some new code; before I commit it, I might decide to
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check it sticks to the guidelines:
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```shell
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rubocop <my new file>
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```
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I can edit make the suggested changes manually, or I can ask Rubocop to fix
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minor issues automatically:
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```
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rubocop --auto-correct
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```
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### Running only certain Cops
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Each community guideline is implemented in a Rubocop 'cop'. When working on a
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legacy codebase you might be swamped with warnings when introducing Rubocop.
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In this case it can often be useful to run only a single cop across the
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codebase, and check those changes in before moving on to the next guideline, for
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example:
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```
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rubocop --auto-correct --only 'Layout/EmptyLineAfterMagicComment'
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```
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### Text Editor Integration
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Rubocop can be integrated with Vim, Visual Studio Code, Atom, and other text editors. A full list can be found [here](https://rubocop.readthedocs.io/en/latest/integration_with_other_tools/).
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