Added remove_index

.gitignore

@@ -7,3 +7,4 @@
 /pkg/
 /spec/reports/
 /tmp/
+*~

.rspec

@@ -1,2 +1,3 @@
 --format documentation
 --color
+--require spec_helper

README.md

@@ -1,41 +1,68 @@
-# Rubocop::Migrations
+# RuboCop Migrations
 
-Welcome to your new gem! In this directory, you'll find the files you need to be able to package up your Ruby library into a gem. Put your Ruby code in the file `lib/rubocop/migrations`. To experiment with that code, run `bin/console` for an interactive prompt.
-
-TODO: Delete this and the text above, and describe your gem
+Rails migrations analysis as a extension of [RuboCop](https://github.com/bbatsov/rubocop). Heavily inspired by [`rubocop-cask`](https://github.com/caskroom/rubocop-cask) which in turn is inspired by [`rubocop-rspec`](https://github.com/nevir/rubocop-rspec).
 
 ## Installation
 
-Add this line to your application's Gemfile:
+Just install the `rubocop-migrations` gem
+
+```bash
+gem install rubocop-migrations
+```
+
+or if you use bundler put this in your `Gemfile`
 
 ```ruby
 gem 'rubocop-migrations'
 ```
 
-And then execute:
 
-    $ bundle
+## Usage
 
-Or install it yourself as:
+You need to tell RuboCop to load the Migrations extension. There are three ways to do this:
 
-    $ gem install rubocop-migrations
+### RuboCop configuration file
 
-## Usage
+Put this into your `.rubocop.yml`:
+
+```yaml
+require: rubocop/migrations
+```
 
-TODO: Write usage instructions here
+Now you can run `rubocop` and it will automatically load the RuboCop Migrations cops together with the standard cops.
 
-## Development
+### Command line
 
-After checking out the repo, run `bin/setup` to install dependencies. Then, run `rake spec` to run the tests. You can also run `bin/console` for an interactive prompt that will allow you to experiment.
+```bash
+rubocop --require rubocop/migrations
+```
+
+## The Cop
+
+All cops are located under [`lib/rubocop/cop/migrations`](lib/rubocop/cop/migrations), and contain examples/documentation.
+
+In your `.rubocop.yml`, you may treat the Cask cops just like any other cop. For example:
 
-To install this gem onto your local machine, run `bundle exec rake install`. To release a new version, update the version number in `version.rb`, and then run `bundle exec rake release`, which will create a git tag for the version, push git commits and tags, and push the `.gem` file to [rubygems.org](https://rubygems.org).
+```yaml
+Migrations/RemoveIndex:
+  Enabled: false
+```
 
 ## Contributing
 
-Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/rubocop-migrations.
+1. Fork it
+2. Create your feature branch (`git checkout -b my-new-feature`)
+3. Commit your changes (`git commit -am 'Add some feature'`)
+4. Push to the branch (`git push origin my-new-feature`)
+5. Create new Pull Request
 
+For running the spec files, this project depends on RuboCop's spec helpers. This means that in order to run the specs locally, you need a (shallow) clone of the RuboCop repository:
 
-## License
+```bash
+git submodule update --init --depth 1 vendor/rubocop
+```
 
-The gem is available as open source under the terms of the [MIT License](http://opensource.org/licenses/MIT).
+## License
 
+`rubocop-migrations` is MIT licensed. [See the accompanying file](MIT-LICENSE.md) for
+the full text.

lib/rubocop/cop/migrations/remove_index.rb

@@ -1,8 +1,31 @@
-module Rubocop
+module RuboCop
   module Cop
     module Migrations
-      # Your code goes here...
+      # Removing indexes is dangerous by nature, if the index you remove
+      # is used extensively, you could end up with database degradation.
+      #
+      # This disallow the use of remove_index at all when. It only allows it
+      # inside a down method definition. If you actually know what you are doing
+      # (usually when the index is not being used) you should explicitly disable
+      # the check by adding a ``rubocop:disable Migrations/RemoveIndex`` comment
+      # in the offending line
       class RemoveIndex < Cop
+        MSG = 'remove_index is disalowed'.freeze
+
+        def_node_matcher :remove_index_found, <<-PATTERN
+           (:send _ :remove_index ...)
+        PATTERN
+
+        def on_send(node)
+          remove_index_found(node) do
+            node.each_ancestor do |a|
+              next unless a.def_type?
+              if a.source =~ /def up/ || a.source =~ /def change/
+                add_offense(node, :selector, MSG)
+              end
+            end
+          end
+        end
       end
     end
   end

lib/rubocop/migrations.rb

@@ -1,7 +1,4 @@
-require "rubocop/migrations/version"
+require 'rubocop'
 
-module Rubocop
-  module Migrations
-    # Your code goes here...
-  end
-end
+# cops
+require 'rubocop/cop/migrations/remove_index'

rubocop-migrations.gemspec

@@ -4,32 +4,25 @@ $LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
 require 'rubocop/migrations/version'
 
 Gem::Specification.new do |spec|
-  spec.name          = "rubocop-migrations"
+  spec.name          = 'rubocop-migrations'
   spec.version       = Rubocop::Migrations::VERSION
-  spec.authors       = ["enricostano"]
-  spec.email         = ["[email protected]"]
 
-  spec.summary       = ""
-  spec.description   = ""
-  spec.homepage      = ""
-  spec.license       = "MIT"
+  spec.authors       = %w(enricostano magec)
+  spec.email         = %w([email protected] [email protected])
 
-  # Prevent pushing this gem to RubyGems.org by setting 'allowed_push_host', or
-  # delete this section to allow pushing this gem to any host.
-  if spec.respond_to?(:metadata)
-    spec.metadata['allowed_push_host'] = "TODO: Set to 'http://mygemserver.com'"
-  else
-    raise "RubyGems 2.0 or newer is required to protect against public gem pushes."
-  end
+  spec.summary       = 'Rails migrations rubocop checks'
+  spec.description   = 'Performs some checks for migration sanity'
+  spec.homepage      = 'https://github.com/redbooth/rubocop-migrations'
+  spec.license       = 'MIT'
 
-  spec.files         = `git ls-files -z`.split("\x0").reject { |f| f.match(%r{^(test|spec|features)/}) }
-  spec.bindir        = "exe"
+  spec.files         = `git ls-files -z`.split("\x0").reject { |f| f.match(%r{^(test|spec|features)/}) } # rubocop:disable Metrics/LineLength
+  spec.bindir        = 'exe'
   spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
-  spec.require_paths = ["lib"]
+  spec.require_paths = ['lib']
 
   spec.add_runtime_dependency 'rubocop', '>= 0.42.0'
 
-  spec.add_development_dependency "bundler", "~> 1.11"
-  spec.add_development_dependency "rake", "~> 10.0"
-  spec.add_development_dependency "rspec", "3.5.0"
+  spec.add_development_dependency 'bundler', '~> 1.11'
+  spec.add_development_dependency 'rake', '~> 10.0'
+  spec.add_development_dependency 'rspec', '3.5.0'
 end

spec/rubocop/cop/migrations/remove_index_spec.rb

@@ -0,0 +1,99 @@
+describe RuboCop::Cop::Migrations::RemoveIndex do
+  include SharedExamples
+  subject(:cop) { described_class.new }
+
+  context 'when there is a remove_index' do
+    context 'in the up method' do
+      let(:source) do
+        <<-MIGRATION
+          class RemoveSomeIndex < ActiveRecord::Migration
+            def up
+              remove_index :some_table, :some_index
+            end
+          end
+        MIGRATION
+      end
+
+      let(:expected_offenses) do
+        [
+          {
+            message: 'remove_index is disalowed',
+            severity: :convention,
+            line: 3,
+            column: 14,
+            source: 'remove_index'
+          }
+        ]
+      end
+
+      include_examples 'reports offenses'
+
+      context 'using method_call syntax' do
+        let(:source) do
+          <<-MIGRATION
+          class RemoveSomeIndex < ActiveRecord::Migration
+            def up
+              change_table :some_table do |m|
+                m.remove_index [:some_index]
+              end
+            end
+          end
+        MIGRATION
+        end
+        let(:expected_offenses) do
+          [
+            {
+              message: 'remove_index is disalowed',
+              severity: :convention,
+              line: 4,
+              column: 18,
+              source: 'remove_index'
+            }
+          ]
+        end
+        include_examples 'reports offenses'
+      end
+    end
+
+    context 'in the change method' do
+      let(:source) do
+        <<-MIGRATION
+          class RemoveSomeIndex < ActiveRecord::Migration
+            def change
+              remove_index :some_table, :some_index
+            end
+          end
+        MIGRATION
+
+      end
+      let(:expected_offenses) do
+        [
+          {
+            message: 'remove_index is disalowed',
+            severity: :convention,
+            line: 3,
+            column: 14,
+            source: 'remove_index'
+          }
+        ]
+      end
+
+      include_examples 'reports offenses'
+    end
+
+    context 'in the down method' do
+      let(:source) do
+          <<-MIGRATION
+          class RemoveSomeIndex < ActiveRecord::Migration
+            def down
+              remove_index :some_table, :some_index
+            end
+          end
+        MIGRATION
+      end
+
+      include_examples 'does not report any offenses'
+    end
+
+  end
+end

spec/spec_helper.rb

@@ -1,2 +1,8 @@
-$LOAD_PATH.unshift File.expand_path('../../lib', __FILE__)
+$LOAD_PATH.unshift File.expand_path('../lib', __FILE__)
+require 'rubocop'
+require 'rubocop/rspec/support'
+
+project_path = File.join(File.dirname(__FILE__), '..')
+Dir["#{project_path}/spec/support/**/*.rb"].each { |f| require f }
+
 require 'rubocop/migrations'

spec/support/shared_examples.rb

@@ -0,0 +1,49 @@
+# inspired on https://github.com/caskroom/rubocop-cask/blob/master/spec/support/cop_shared_examples.rb
+# sed 's/inspired on/copied from/g
+#
+module SharedExamples
+  shared_examples 'does not report any offenses' do
+    it 'does not report any offenses' do
+      expect_no_offenses(cop, source)
+    end
+  end
+
+  shared_examples 'reports offenses' do
+    it 'reports offenses' do
+      expect_reported_offenses(cop, source, expected_offenses)
+    end
+  end
+
+  shared_examples 'autocorrects source' do
+    it 'autocorrects source' do
+      expect_autocorrected_source(cop, source, correct_source)
+    end
+  end
+
+  def expect_no_offenses(cop, source)
+    inspect_source(cop, source)
+    expect(cop.offenses).to be_empty
+  end
+
+  def expect_reported_offenses(cop, source, expected_offenses)
+    inspect_source(cop, source)
+    expect(cop.offenses.size).to eq(expected_offenses.size)
+    expected_offenses.zip(cop.offenses).each do |expected, actual|
+      expect_offense(expected, actual)
+    end
+  end
+
+  # rubocop:disable Metrics/AbcSize
+  def expect_offense(expected, actual)
+    expect(actual.message).to eq(expected[:message])
+    expect(actual.severity).to eq(expected[:severity])
+    expect(actual.line).to eq(expected[:line])
+    expect(actual.column).to eq(expected[:column])
+    expect(actual.location.source).to eq(expected[:source])
+  end
+
+  def expect_autocorrected_source(cop, source, correct_source)
+    new_source = autocorrect_source(cop, source)
+    expect(new_source).to eq(Array(correct_source).join("\n"))
+  end
+end