WIP: Add custom cop for ArrayLiteralDelimiterrs-array-literal-delimiter-cop

3 files changed, 148 insertions, 1 deletions

diff --git a/.rubocop.yml b/.rubocop.yml
index 2d8eb4077f3..fdca6e5141a 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -1,4 +1,6 @@
-require: rubocop-rspec
+require:
+  - rubocop-rspec
+  - ./lib/rubocop/cop/style/array_literal_delimiter.rb
 
 AllCops:
   TargetRubyVersion: 2.1
diff --git a/lib/rubocop/cop/style/array_literal_delimiter.rb b/lib/rubocop/cop/style/array_literal_delimiter.rb
new file mode 100644
index 00000000000..1b0638ce26c
--- /dev/null
+++ b/lib/rubocop/cop/style/array_literal_delimiter.rb
@@ -0,0 +1,43 @@
+# encoding: utf-8
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module Style
+      # This cop enforces square brackets for Array literal `%`-style
+      # delimiters.
+      #
+      # @example
+      #
+      #   # bad
+      #   %w(foo bar) + %w{baz qux}
+      #
+      #   # good
+      #   %w[foo bar] + %w[baz qux]
+      class ArrayLiteralDelimiter < RuboCop::Cop::Cop
+        def on_array(*args)
+          array = args.first
+
+          first, last = array.loc.begin, array.loc.end
+
+          return unless first && last
+          return unless first.source.start_with?('%')
+
+          return if first.source.start_with?('%w[', '%W[', '%i[', '%I[') &&
+            last.source == ']'
+
+          add_offense(array, :expression, "TODO")
+        end
+
+        def autocorrect(node)
+          -> (corrector) do
+            style = node.loc.begin.source[0..-2]
+
+            corrector.replace(node.loc.begin, "#{style}[")
+            corrector.replace(node.loc.end, ']')
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/spec/lib/rubocop/cop/style/array_literal_delimiter_spec.rb b/spec/lib/rubocop/cop/style/array_literal_delimiter_spec.rb
new file mode 100644
index 00000000000..3a11dd07127
--- /dev/null
+++ b/spec/lib/rubocop/cop/style/array_literal_delimiter_spec.rb
@@ -0,0 +1,102 @@
+require 'spec_helper'
+
+require 'rubocop'
+require 'rubocop/cop/style/array_literal_delimiter'
+
+# encoding: utf-8
+# frozen_string_literal: true
+
+require 'tempfile'
+
+module CopHelper
+  extend RSpec::SharedContext
+
+  let(:ruby_version) { 2.2 }
+
+  def inspect_source_file(cop, source)
+    Tempfile.open('tmp') { |f| inspect_source(cop, source, f) }
+  end
+
+  def inspect_source(cop, source, file = nil)
+    if source.is_a?(Array) && source.size == 1
+      raise "Don't use an array for a single line of code: #{source}"
+    end
+    RuboCop::Formatter::DisabledConfigFormatter.config_to_allow_offenses = {}
+    RuboCop::Formatter::DisabledConfigFormatter.detected_styles = {}
+    processed_source = parse_source(source, file)
+    raise 'Error parsing example code' unless processed_source.valid_syntax?
+    _investigate(cop, processed_source)
+  end
+
+  def parse_source(source, file = nil)
+    source = source.join($RS) if source.is_a?(Array)
+
+    if file && file.respond_to?(:write)
+      file.write(source)
+      file.rewind
+      file = file.path
+    end
+
+    RuboCop::ProcessedSource.new(source, ruby_version, file)
+  end
+
+  def autocorrect_source_file(cop, source)
+    Tempfile.open('tmp') { |f| autocorrect_source(cop, source, f) }
+  end
+
+  def autocorrect_source(cop, source, file = nil)
+    cop.instance_variable_get(:@options)[:auto_correct] = true
+    processed_source = parse_source(source, file)
+    _investigate(cop, processed_source)
+
+    corrector =
+      RuboCop::Cop::Corrector.new(processed_source.buffer, cop.corrections)
+    corrector.rewrite
+  end
+
+  def _investigate(cop, processed_source)
+    forces = RuboCop::Cop::Force.all.each_with_object([]) do |klass, instances|
+      next unless cop.join_force?(klass)
+      instances << klass.new([cop])
+    end
+
+    commissioner =
+      RuboCop::Cop::Commissioner.new([cop], forces, raise_error: true)
+    commissioner.investigate(processed_source)
+    commissioner
+  end
+end
+
+module RuboCop
+  module Cop
+    class Cop
+      def messages
+        offenses.sort.map(&:message)
+      end
+
+      def highlights
+        offenses.sort.map { |o| o.location.source }
+      end
+    end
+  end
+end
+
+describe RuboCop::Cop::Style::ArrayLiteralDelimiter do
+  include CopHelper
+
+  subject(:cop) { described_class.new }
+
+  it 'does something' do
+    inspect_source(cop, '%w{foo bar baz}')
+
+    expect(cop.offenses.size).to eq(1)
+    expect(cop.offenses.map(&:line).sort).to eq([1])
+    expect(cop.highlights).to eq(['%w{foo bar baz}'])
+  end
+
+  it 'does something else' do
+    inspect_source(cop, '%w[foo bar baz]')
+
+    expect(cop.offenses.size).to eq(0)
+  end
+end