Pronto-Labelman

Pronto runner for automatically adding labels to Github Pull Requests.

Use Case

• You want to automate decision-making and addition of labels to Github PR's, e.g., if a PR contains .HTML files, automatically tag it for Design review.
• You are already using pronto with Github

How it Works

Simple, really. It acts as a pronto runner, giving it visibility over the payload of a pull request. It then tries to find classes that are 1. under the namespace Pronto::LabelmanRules and 2.) extend the Pronto::LabelmanRules::Rule class.

These rule classes, which are to be implemented by users of this gem, will be responsible for inspecting the pull request payload and deciding whether to associate it with a particular label (more on this later).

Prerequisites

• Properly-configured pronto environment

Installation

Install the gem

gem install pronto-labelman

Invoke from pronto. Set github_pr_label as formatter (-f) and labelman as runner (-r)

pronto run -f github_pr_label -c $BASE_BRANCH_SHA -r labelman

If you want to specify a temporary path where to look for rules, use the LABELMAN_RULES environment variable

export LABELMAN_RULES=path/to/custom/pronto/labelman_rules
pronto run -f github_pr_label -c $BASE_BRANCH_SHA -r labelman

Technical Details

• Introduces a new formatter called Pronto::Formatter::GithubPRLabelFormatter. Unlike the built-in formatters in pronto that post comments on a Pull Request, this formatter attaches labels. Pronto does not come pre-package with something like that so I had to make my own.
• Moreover, because formatter types are hardcoded in Pronto::Formatter, I had to monkey-patch that class to add my custom formatter 'Pronto::Formatter::GithubPRLabelFormatter`.
• Still related to that, pronto's Github client does not expose an API with interacting with labels on an issue (like a pull request), so I had to again monkey patch its Github client Pronto::Github to add a method that exposes the add a label API.

Creating Rules

1. Subclass Pronto::LabelmanRules::Rule. Make sure your subclass is in the namespace Pronto::LabelmanRules

module Pronto
  module LabelmanRules
    class MyCustomRule < Rule
    end
  end
end

2. Define a label using the label class method. This should match the name of the label that will be applied

module Pronto
  module LabelmanRules
    class MyCustomRule < Rule
      label 'Needs Code Review'
    end
  end
end

3. Implement the applicable? method. It should return a boolean signifying whether the label must be applied or not. You have access to the @patches attribute, signifying the changes

module Pronto
  module LabelmanRules
    class MyCustomRule < Rule
      label 'Needs Code Review'
      
      def applicable?
        # Apply a label if the patches is not empty.
        # Simple, dumb rule, yes, but it's just for purposes of illustration
        true unless @patches.empty?
      end
    end
  end
end

4. Make sure this class is in the load path or use the LABELMAN_RULES environment to tell Labelman where to find it

export LABELMAN_RULES=custom/pronto/labelman_rules

Todo List

• Improve "monkey patching"
• Improve logging (do not use p)
• More configuration