Add `bin/feature-flag` script

This helps with creating a new
feature flag in repository
by asking a bunch of questions
to put into the YAML definition

bin/feature-flag

+#!/usr/bin/env ruby
+#
+# Generate a feature flag entry file in the correct location.
+#
+# Automatically stages the file and amends the previous commit if the `--amend`
+# argument is used.
+
+require 'optparse'
+require 'yaml'
+require 'fileutils'
+require 'cgi'
+
+require_relative '../lib/feature/shared' unless defined?(Feature::Shared)
+
+Options = Struct.new(
+  :name,
+  :type,
+  :group,
+  :ee,
+  :amend,
+  :dry_run,
+  :force,
+  :introduced_by_url,
+  :rollout_issue_url
+)
+
+module FeatureFlagHelpers
+  Abort = Class.new(StandardError)
+  Done = Class.new(StandardError)
+
+  def capture_stdout(cmd)
+    output = IO.popen(cmd, &:read)
+    fail_with "command failed: #{cmd.join(' ')}" unless $?.success?
+    output
+  end
+
+  def fail_with(message)
+    raise Abort, "\e[31merror\e[0m #{message}"
+  end
+end
+
+class FeatureFlagOptionParser
+  extend FeatureFlagHelpers
+  extend ::Feature::Shared
+
+  class << self
+    def parse(argv)
+      options = Options.new
+
+      parser = OptionParser.new do |opts|
+        opts.banner = "Usage: #{__FILE__} [options] <feature-flag>\n\n"
+
+        # Note: We do not provide a shorthand for this in order to match the `git
+        # commit` interface
+        opts.on('--amend', 'Amend the previous commit') do |value|
+          options.amend = value
+        end
+
+        opts.on('-f', '--force', 'Overwrite an existing entry') do |value|
+          options.force = value
+        end
+
+        opts.on('-m', '--introduced-by-url [string]', String, 'URL to Merge Request introducing Feature Flag') do |value|
+          options.introduced_by_url = value
+        end
+
+        opts.on('-i', '--rollout-issue-url [string]', String, 'URL to Issue rolling out Feature Flag') do |value|
+          options.rollout_issue_url = value
+        end
+
+        opts.on('-n', '--dry-run', "Don't actually write anything, just print") do |value|
+          options.dry_run = value
+        end
+
+        opts.on('-g', '--group [string]', String, "The group introducing a feature flag, like: `group::apm`") do |value|
+          options.group = value if value.start_with?('group::')
+        end
+
+        opts.on('-t', '--type [string]', String, "The category of the feature flag, valid options are: #{TYPES.keys.map(&:to_s).join(', ')}") do |value|
+          options.type = value.to_sym if TYPES[value.to_sym]
+        end
+
+        opts.on('-e', '--ee', 'Generate a feature flag entry for GitLab EE') do |value|
+          options.ee = value
+        end
+
+        opts.on('-h', '--help', 'Print help message') do
+          $stdout.puts opts
+          raise Done.new
+        end
+      end
+
+      parser.parse!(argv)
+
+      unless argv.one?
+        $stdout.puts parser.help
+        $stdout.puts
+        raise Abort, 'Feature flag name is required'
+      end
+
+      # Name is a first name
+      options.name = argv.first
+
+      options
+    end
+
+    def read_group
+      $stdout.puts ">> Please specify the group introducing feature flag, like `group::apm`:"
+
+      loop do
+        $stdout.print "\n?> "
+        group = $stdin.gets.strip
+        group = nil if group.empty?
+        return group if group.nil? || group.start_with?('group::')
+
+        $stderr.puts "Group needs to include `group::`"
+      end
+    end
+
+    def read_type
+      $stdout.puts ">> Please specify the type of your feature flag:"
+      $stdout.puts
+      TYPES.each do |type, data|
+        $stdout.puts "#{type.to_s.rjust(15)}#{' '*6}#{data[:description]}"
+      end
+
+      loop do
+        $stdout.print "\n?> "
+
+        type = $stdin.gets.strip.to_sym
+        return type if TYPES[type]
+
+        $stderr.puts "Invalid type specified '#{type}'"
+      end
+    end
+
+    def read_issue_url(options)
+      return unless TYPES.dig(options.type, :rollout_issue)
+
+      url = "https://gitlab.com/gitlab-org/gitlab/-/issues/new"
+      title = "[Feature flag] Rollout of `#{options.name}`"
+      description = File.read('.gitlab/issue_templates/Feature Flag Roll Out.md')
+      description.sub!(':feature_name', options.name)
+
+      issue_new_url = url + "?" +
+        "issue[title]=" + CGI.escape(title) + "&"
+        # TODO: We should be able to pick `issueable_template`
+        # + "issue[description]=" + CGI.escape(description)
+
+      $stdout.puts ">> Open this URL and fill the rest of details:"
+      $stdout.puts issue_new_url
+      $stdout.puts
+
+      $stdout.puts ">> Paste URL here, or enter to skip:"
+
+      loop do
+        $stdout.print "\n?> "
+        created_url = $stdin.gets.strip
+        created_url = nil if created_url.empty?
+        return created_url if created_url.nil? || created_url.start_with?('https://')
+
+        $stderr.puts "URL needs to start with https://"
+      end
+    end
+  end
+end
+
+class FeatureFlagCreator
+  include FeatureFlagHelpers
+
+  attr_reader :options
+
+  def initialize(options)
+    @options = options
+  end
+
+  def execute
+    assert_feature_branch!
+    assert_name!
+    assert_existing_feature_flag!
+
+    # Read type from $stdin unless is already set
+    options.type ||= FeatureFlagOptionParser.read_type
+    options.group ||= FeatureFlagOptionParser.read_group
+    options.rollout_issue_url ||= FeatureFlagOptionParser.read_issue_url(options)
+
+    $stdout.puts "\e[32mcreate\e[0m #{file_path}"
+    $stdout.puts contents
+
+    unless options.dry_run
+      write
+      amend_commit if options.amend
+    end
+
+    if editor
+      system("#{editor} '#{file_path}'")
+    end
+  end
+
+  private
+
+  def contents
+    YAML.dump(
+      'name'              => options.name,
+      'introduced_by_url' => options.introduced_by_url,
+      'rollout_issue_url' => options.rollout_issue_url,
+      'group'             => options.group.to_s,
+      'type'              => options.type.to_s,
+      'default_enabled'   => false
+    ).strip
+  end
+
+  def write
+    FileUtils.mkdir_p(File.dirname(file_path))
+    File.write(file_path, contents)
+  end
+
+  def editor
+    ENV['EDITOR']
+  end
+
+  def amend_commit
+    fail_with "git add failed" unless system(*%W[git add #{file_path}])
+
+    Kernel.exec(*%w[git commit --amend])
+  end
+
+  def assert_feature_branch!
+    return unless branch_name == 'master'
+
+    fail_with "Create a branch first!"
+  end
+
+  def assert_existing_feature_flag!
+    existing_path = all_feature_flag_names[options.name]
+    return unless existing_path
+    return if options.force
+
+    fail_with "#{existing_path} already exists! Use `--force` to overwrite."
+  end
+
+  def assert_name!
+    return if options.name.match(/\A[a-z0-9_-]+\Z/)
+
+    fail_with "Provide a name for the feature flag that is [a-z0-9_-]"
+  end
+
+  def file_path
+    feature_flags_paths.last
+      .sub('**', options.type.to_s)
+      .sub('*.yml', options.name + '.yml')
+  end
+
+  def all_feature_flag_names
+    @all_feature_flag_names ||=
+      feature_flags_paths.map do |glob_path|
+        Dir.glob(glob_path).map do |path|
+          [File.basename(path, '.yml'), path]
+        end
+      end.flatten(1).to_h
+  end
+
+  def feature_flags_paths
+    paths = []
+    paths << File.join('config', 'feature_flags', '**', '*.yml')
+    paths << File.join('ee', 'config', 'feature_flags', '**', '*.yml') if ee?
+    paths
+  end
+
+  def ee?
+    options.ee
+  end
+
+  def branch_name
+    @branch_name ||= capture_stdout(%w[git symbolic-ref --short HEAD]).strip
+  end
+end
+
+if $0 == __FILE__
+  begin
+    options = FeatureFlagOptionParser.parse(ARGV)
+    FeatureFlagCreator.new(options).execute
+  rescue FeatureFlagHelpers::Abort => ex
+    $stderr.puts ex.message
+    exit 1
+  rescue FeatureFlagHelpers::Done
+    exit
+  end
+end
+
+# vim: ft=ruby

spec/bin/feature_flag_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+load File.expand_path('../../bin/feature-flag', __dir__)
+
+RSpec.describe 'bin/feature-flag' do
+  using RSpec::Parameterized::TableSyntax
+
+  describe FeatureFlagCreator do
+    let(:argv) { %w[feature-flag-name -t development -g group::memory -i https://url] }
+    let(:options) { FeatureFlagOptionParser.parse(argv) }
+    let(:creator) { described_class.new(options) }
+    let(:existing_flag) { File.join('config', 'feature_flags', 'development', 'existing-feature-flag.yml') }
+
+    before do
+      # create a dummy feature flag
+      FileUtils.mkdir_p(File.dirname(existing_flag))
+      File.write(existing_flag, '{}')
+
+      # ignore writes
+      allow(File).to receive(:write).and_return(true)
+
+      # ignore stdin
+      allow($stdin).to receive(:gets).and_raise('EOF')
+
+      # ignore Git commands
+      allow(creator).to receive(:branch_name) { 'feature-branch' }
+    end
+
+    after do
+      FileUtils.rm_f(existing_flag)
+    end
+
+    subject { creator.execute }
+
+    it 'properly creates a feature flag' do
+      expect(File).to receive(:write).with(
+        File.join('config', 'feature_flags', 'development', 'feature-flag-name.yml'),
+        anything)
+
+      expect do
+        subject
+      end.to output(/name: feature-flag-name/).to_stdout
+    end
+
+    context 'when running on master' do
+      it 'requires feature branch' do
+        expect(creator).to receive(:branch_name) { 'master' }
+
+        expect { subject }.to raise_error(FeatureFlagHelpers::Abort, /Create a branch first/)
+      end
+    end
+
+    context 'validates feature flag name' do
+      where(:argv, :ex) do
+        %w[.invalid.feature.flag] | /Provide a name for the feature flag that is/
+        %w[existing-feature-flag] | /already exists!/
+      end
+
+      with_them do
+        it do
+          expect { subject }.to raise_error(ex)
+        end
+      end
+    end
+  end
+
+  describe FeatureFlagOptionParser do
+    describe '.parse' do
+      where(:param, :argv, :result) do
+        :name              | %w[foo]                                 | 'foo'
+        :amend             | %w[foo --amend]                         | true
+        :force             | %w[foo -f]                              | true
+        :force             | %w[foo --force]                         | true
+        :ee                | %w[foo -e]                              | true
+        :ee                | %w[foo --ee]                            | true
+        :introduced_by_url | %w[foo -m https://url]                  | 'https://url'
+        :introduced_by_url | %w[foo --introduced-by-url https://url] | 'https://url'
+        :rollout_issue_url | %w[foo -i https://url]                  | 'https://url'
+        :rollout_issue_url | %w[foo --rollout-issue-url https://url] | 'https://url'
+        :dry_run           | %w[foo -n]                              | true
+        :dry_run           | %w[foo --dry-run]                       | true
+        :type              | %w[foo -t development]                  | :development
+        :type              | %w[foo --type development]              | :development
+        :type              | %w[foo -t invalid]                      | nil
+        :type              | %w[foo --type invalid]                  | nil
+        :group             | %w[foo -g group::memory]                | 'group::memory'
+        :group             | %w[foo --group group::memory]           | 'group::memory'
+        :group             | %w[foo -g invalid]                      | nil
+        :group             | %w[foo --group invalid]                 | nil
+      end
+
+      with_them do
+        it do
+          options = described_class.parse(Array(argv))
+
+          expect(options.public_send(param)).to eq(result)
+        end
+      end
+
+      it 'missing feature flag name' do
+        expect do
+          expect { described_class.parse(%w[--amend]) }.to output(/Feature flag name is required/).to_stdout
+        end.to raise_error(FeatureFlagHelpers::Abort)
+      end
+
+      it 'parses -h' do
+        expect do
+          expect { described_class.parse(%w[foo -h]) }.to output(/Usage:/).to_stdout
+        end.to raise_error(FeatureFlagHelpers::Done)
+      end
+    end
+
+    describe '.read_type' do
+      let(:type) { 'development' }
+
+      it 'reads type from $stdin' do
+        expect($stdin).to receive(:gets).and_return(type)
+        expect do
+          expect(described_class.read_type).to eq(:development)
+        end.to output(/specify the type/).to_stdout
+      end
+
+      context 'invalid type given' do
+        let(:type) { 'invalid' }
+
+        it 'shows error message and retries' do
+          expect($stdin).to receive(:gets).and_return(type)
+          expect($stdin).to receive(:gets).and_raise('EOF')
+
+          expect do
+            expect { described_class.read_type }.to raise_error(/EOF/)
+          end.to output(/specify the type/).to_stdout
+            .and output(/Invalid type specified/).to_stderr
+        end
+      end
+    end
+
+    describe '.read_group' do
+      let(:group) { 'group::memory' }
+
+      it 'reads type from $stdin' do
+        expect($stdin).to receive(:gets).and_return(group)
+        expect do
+          expect(described_class.read_group).to eq('group::memory')
+        end.to output(/specify the group/).to_stdout
+      end
+
+      context 'invalid group given' do
+        let(:type) { 'invalid' }
+
+        it 'shows error message and retries' do
+          expect($stdin).to receive(:gets).and_return(type)
+          expect($stdin).to receive(:gets).and_raise('EOF')
+
+          expect do
+            expect { described_class.read_group }.to raise_error(/EOF/)
+          end.to output(/specify the group/).to_stdout
+            .and output(/Group needs to include/).to_stderr
+        end
+      end
+    end
+
+    describe '.rollout_issue_url' do
+      let(:options) { OpenStruct.new(name: 'foo', type: :development) }
+      let(:url) { 'https://issue' }
+
+      it 'reads type from $stdin' do
+        expect($stdin).to receive(:gets).and_return(url)
+        expect do
+          expect(described_class.read_issue_url(options)).to eq('https://issue')
+        end.to output(/Paste URL here/).to_stdout
+      end
+
+      context 'invalid URL given' do
+        let(:type) { 'invalid' }
+
+        it 'shows error message and retries' do
+          expect($stdin).to receive(:gets).and_return(type)
+          expect($stdin).to receive(:gets).and_raise('EOF')
+
+          expect do
+            expect { described_class.read_issue_url(options) }.to raise_error(/EOF/)
+          end.to output(/Paste URL here/).to_stdout
+            .and output(/URL needs to start/).to_stderr
+        end
+      end
+    end
+  end
+end