Use Synvert to automatically upgrade rails 4.2 to 5.0 (Part 3)

• Use Synvert to automatically upgrade rails 4.2 to 5.0 (Part 1)

• Use Synvert to automatically upgrade rails 4.2 to 5.0 (Part 2)

• Use Synvert to automatically upgrade rails 4.2 to 5.0 (Part 3) (you are here)

Welcome to the final installment of our serial upgrading rails 4.2 to 5.0 tutorials. I will guide you through the process of writing and testing your own Synvert snippet.

Rails 5 has added three alias after_create_commit, after_update_commit and after_destroy_commit

Before Rails 5:

after_commit :add_to_index_later, on: :create, if: :can_add?
after_commit :update_in_index_later, on: :update
after_commit :remove_from_index_later, on: :destroy

After Rails 5:

after_create_commit :add_to_index_later, if: :can_add?
after_update_commit :update_in_index_later
after_destroy_commit :remove_from_index_later

It’s cleaner. Let’s write a snippet to upgrade the code.

First, nagivate to the synvert-snippet-ruby repository, if you don’t have it yet, you can clone it from github

cd synvert-snippets-ruby

It provides some utilities to test the snippet. We can run

synvert-ruby -g rails/use_after_commit_alias

to generate a template snippet in lib/rails/use_after_commit_alias.rb

# frozen_string_literal: true

Synvert::Rewriter.new 'rails', 'use_after_commit_alias' do
  description <<~EOS
    It converts Foo to Bar

    ```ruby
    Foo
    ```

    =>

    ```ruby
    Bar
    ```
  EOS

  within_files '**/*.rb' do
    with_node type: 'const', to_source: 'Foo' do
      replace_with 'Bar'
    end
  end
end

and test code in spec/rails/use_after_commit_alias_spec.rb

# frozen_string_literal: true

require 'spec_helper'

RSpec.describe 'Convert Foo to Bar' do
  let(:rewriter_name) { 'rails/use_after_commit_alias' }
  let(:fake_file_path) { 'foobar.rb' }
  let(:test_content) { 'Foo' }
  let(:test_rewritten_content) { 'Bar' }

  include_examples 'convertable'
end

In my experience, I have found that incorporating test-driven development when building a snippet can be highly effective. Let’s run the test command.

bundle exec guard

It continuously monitors both the snippet code and test code, which means that whenever changes are made to the code, it will automatically rerun the test.

To begin constructing our snippet, let’s update the case.

# frozen_string_literal: true

require 'spec_helper'

RSpec.describe 'Convert Foo to Bar' do
  let(:rewriter_name) { 'rails/use_after_commit_alias' }
  let(:fake_file_path) { 'app/models/post.rb' }
  let(:test_content) { <<~EOS }
    class Post < ApplicationRecord
      after_commit :add_to_index_later, on: :create, if: :can_add?
      after_commit :update_in_index_later, on: :update
      after_commit :remove_from_index_later, on: :destroy
    end
  EOS

  let(:test_rewritten_content) { <<~EOS }
    class Post < ApplicationRecord
      after_create_commit :add_to_index_later, if: :can_add?
      after_update_commit :update_in_index_later
      after_destroy_commit :remove_from_index_later
    end
  EOS

  include_examples 'convertable'
end

The test has failed.

@@ -1,6 +1,6 @@
class Post < ApplicationRecord
-  after_create_commit :add_to_index_later, if: :can_add?
-  after_update_commit :update_in_index_later
-  after_destroy_commit :remove_from_index_later
+  after_commit :add_to_index_later, on: :create, if: :can_add?
+  after_commit :update_in_index_later, on: :update
+  after_commit :remove_from_index_later, on: :destroy
end

To resolve the test failure, we can take advantage of the VSCode Synvert extension. It allows us to quickly and easily locate the node that needs to be replaced, and generate a corresponding snippet.

Open the VSCode Synvert Extension. Select the language as ruby and click “Show Generate Snippet Form”.

Set the File Pattern as app/models/**/*.rb

Set the Gem Version as activerecord >= 5.0

Set the Input as after_commit :add_to_index_later, on: :create, if: :can_add?

Set the Output as after_create_commit :add_to_index_later, if: :can_add?

Click the “Generate Snippet” button, then it will generate the following snippet:

Synvert::Rewriter.new 'group', 'name' do
  if_gem 'activerecord', '>= 5.0'
  within_files 'app/models/**/*.rb' do
    with_node node_type: 'send', receiver: nil, message: 'after_commit', arguments: { size: 2, '0': :add_to_index_later, '1': { node_type: 'hash', on_value: :create, if_value: :can_add? } } do
      replace "arguments.1", with: 'if: {{arguments.1.if_source}}'
      replace :message, with: 'after_create_commit'
    end
  end
end

We can copy the snippet to lib/rails/use_after_commit_alias.rb and make some changes.

We don’t care about the value of the first argument, so we can remove the arguments.0 rule.

Second argument must be a hash node, it must have on key and its value should be one of the :create, :update and :destroy, so we can say on_value: { in: [:create, :update, :destroy] }. We don’t care if it has if key, so we can remove the if_value rule.

Instead of replace ‘arguments.1’, we can use delete 'argunments.1.on_pair', and_comma: true to delete the on key.

Then replace the message with after_{{arguments.1.on_value}}_commit.

Synvert::Rewriter.new 'rails', 'use_after_commit_alias' do
  if_gem 'activerecord', '>= 5.0'
  within_files 'app/models/**/*.rb' do
    with_node node_type: 'send', receiver: nil, message: 'after_commit',
              arguments: { size: 2, '1': { node_type: 'hash', on_value: { in: %i[create update destroy] } } } do
      delete 'arguments.1.on_pair', and_comma: true
      replace :message, with: 'after_{{arguments.1.on_value}}_commit'
    end
  end
end

The test has passed.

Let’s try the snippet in our project. We can simply copy and paste it into the VSCode Synvert extension, then click the “Search” button.

And replace them all.

Use keywords arguments in HTTP request methods

Before Rails 5:

def test_show
  get user_path, { id: user.id }, { admin: user.admin? }, { notice: 'Welcome' }
  asssert_response :success
end

After Rails 5:

def test_show
  get user_path, params: { id: user.id }, session: { admin: user.admin? }, flash: { notice: 'Welcome' }
  asssert_response :success
end

This makes it easier to understand what arguments are being passed.

Let’s generate a new snippet.

synvert-ruby -g rails/use_keywords_arguments_in_http_request_methods

And add first test case

context 'get request' do
  let(:rewriter_name) { 'rails/use_keywords_arguments_in_http_request_methods' }
  let(:fake_file_path) { 'spec/controllers/users_controller_spec.rb' }
  let(:test_content) { <<~EOS }
    def test_show
      get user_path, { id: user.id }, { admin: user.admin? }, { notice: 'Welcome' }
      asssert_response :success
    end
  EOS
  let(:test_rewritten_content) { <<~EOS }
    def test_show
      get user_path, params: { id: user.id }, session: { admin: user.admin? }, flash: { notice: 'Welcome' }
      asssert_response :success
    end
  EOS

  include_examples 'convertable'
end

The test has failed.

@@ -1,5 +1,5 @@
 def test_show
-  get user_path, params: { id: user.id }, session: { admin: user.admin? }, flash: { notice: 'Welcome' }
+  get user_path, { id: user.id }, { admin: user.admin? }, { notice: 'Welcome' }
   asssert_response :success
 end

Let’s use the VSCode Synvert extension,

Set the File Pattern as spec/controllers/**/*_spec.rb

Set the Gem Version as actionpack >= 5.0

Set the Input as get user_path, { id: user.id }, { admin: user.admin? }, { notice: 'Welcome' }

Set the Output as get user_path, params: { id: user.id }, session: { admin: user.admin? }, flash: { notice: 'Welcome' }

Click the “Generate Snippet” button, then it will generate the following snippet:

Synvert::Rewriter.new 'group', 'name' do
  within_files 'spec/controllers/**/*_spec.rb' do
    with_node node_type: 'send', receiver: nil, message: 'get', arguments: { size: 4, '0': { node_type: 'send', receiver: nil, message: 'user_path', arguments: { size: 0 } }, '1': { node_type: 'hash', id_value: { node_type: 'send', receiver: { node_type: 'send', receiver: nil, message: 'user', arguments: { size: 0 } }, message: 'id', arguments: { size: 0 } } }, '2': { node_type: 'hash', admin_value: { node_type: 'send', receiver: { node_type: 'send', receiver: nil, message: 'user', arguments: { size: 0 } }, message: 'admin?', arguments: { size: 0 } } }, '3': { node_type: 'hash', notice_value: "'Welcome'" } } do
      replace :arguments, with: '{{arguments.0}}, params: {{arguments.1}}, session: {{arguments.2}}, flash: {{arguments.3}}'
    end
  end
end

It doesn’t matter what the arguments are, just leave arguments.size rule.

Synvert::Rewriter.new 'rails', 'use_keywords_arguments_in_http_request_methods' do
  if_gem 'actionpack', '>= 5.0'
  within_files 'spec/controllers/**/*_spec.rb' do
    with_node node_type: 'send', receiver: nil, message: 'get', arguments: { size: 4 } do
      replace :arguments, with: '{{arguments.0}}, params: {{arguments.1}}, session: {{arguments.2}}, flash: {{arguments.3}}'
    end
  end
end

The test has passed. Let’s add a new test case which doesn’t have flash argument.

context 'get request without flash' do
  let(:rewriter_name) { 'rails/use_keywords_arguments_in_http_request_methods' }
  let(:fake_file_path) { 'spec/controllers/users_controller_spec.rb' }
  let(:test_content) { <<~EOS }
    def test_show
      get user_path, { id: user.id }, { admin: user.admin? }
      asssert_response :success
    end
  EOS
  let(:test_rewritten_content) { <<~EOS }
    def test_show
      get user_path, params: { id: user.id }, session: { admin: user.admin? }
      asssert_response :success
    end
  EOS

  include_examples 'convertable'
end

It failed again. We can simply add a new with_node to handle 3 arguments case.

Synvert::Rewriter.new 'rails', 'use_keywords_arguments_in_http_request_methods' do
  if_gem 'actionpack', '>= 5.0'
  within_files 'spec/controllers/**/*_spec.rb' do
    with_node node_type: 'send', receiver: nil, message: 'get', arguments: { size: 4 } do
      replace :arguments, with: '{{arguments.0}}, params: {{arguments.1}}, session: {{arguments.2}}, flash: {{arguments.3}}'
    end
    with_node node_type: 'send', receiver: nil, message: 'get', arguments: { size: 3 } do
      replace :arguments, with: '{{arguments.0}}, params: {{arguments.1}}, session: {{arguments.2}}'
    end
  end
end

The tests are passed now. Let’s add a new test case which doesn’t have session argument.

context 'get request without session' do
  let(:rewriter_name) { 'rails/use_keywords_arguments_in_http_request_methods' }
  let(:fake_file_path) { 'spec/controllers/users_controller_spec.rb' }
  let(:test_content) { <<~EOS }
    def test_show
      get user_path, { id: user.id }
      asssert_response :success
    end
  EOS
  let(:test_rewritten_content) { <<~EOS }
    def test_show
      get user_path, params: { id: user.id }
      asssert_response :success
    end
  EOS

  include_examples 'convertable'
end

Tests failed again. We can simply add a new with_node to handle 2 arguments case.

Synvert::Rewriter.new 'rails', 'use_keywords_arguments_in_http_request_methods' do
  if_gem 'actionpack', '>= 5.0'
  within_files 'spec/controllers/**/*_spec.rb' do
    with_node node_type: 'send', receiver: nil, message: 'get', arguments: { size: 4 } do
      replace :arguments, with: '{{arguments.0}}, params: {{arguments.1}}, session: {{arguments.2}}, flash: {{arguments.3}}'
    end
    with_node node_type: 'send', receiver: nil, message: 'get', arguments: { size: 3 } do
      replace :arguments, with: '{{arguments.0}}, params: {{arguments.1}}, session: {{arguments.2}}'
    end
    with_node node_type: 'send', receiver: nil, message: 'get', arguments: { size: 2 } do
      replace :arguments, with: '{{arguments.0}}, params: {{arguments.1}}'
    end
  end
end

Once again, our test cases have passed successfully. So far we have handled all the cases of get request, let’s do a simple refactor, with_node just checks arguments.size is greater than 1, then we use case when to call different replace methods.

Synvert::Rewriter.new 'rails', 'use_keywords_arguments_in_http_request_methods' do
  if_gem 'actionpack', '>= 5.0'
  within_files 'spec/controllers/**/*_spec.rb' do
    with_node node_type: 'send', receiver: nil, message: 'get', arguments: { size: { gt: 1 } } do
      case current_node.arguments.size
      when 4
        replace :arguments, with: '{{arguments.0}}, params: {{arguments.1}}, session: {{arguments.2}}, flash: {{arguments.3}}'
      when 3
        replace :arguments, with: '{{arguments.0}}, params: {{arguments.1}}, session: {{arguments.2}}'
      when 2
        replace :arguments, with: '{{arguments.0}}, params: {{arguments.1}}'
      end
    end
  end
end

Our tests are still passed. Let’s add a new test case to use post request.

context 'post request' do
  let(:rewriter_name) { 'rails/use_keywords_arguments_in_http_request_methods' }
  let(:fake_file_path) { 'spec/controllers/users_controller_spec.rb' }
  let(:test_content) { <<~EOS }
    def test_create
      post users_path, { name: 'user' }, { admin: true }
      asssert_response :success
    end
  EOS
  let(:test_rewritten_content) { <<~EOS }
    def test_create
      post users_path, params: { name: 'user' }, session: { admin: true }
      asssert_response :success
    end
  EOS

  include_examples 'convertable'
end

The test has failed, but it can be simply fixed by using in operator to find message.

Synvert::Rewriter.new 'rails', 'use_keywords_arguments_in_http_request_methods' do
  if_gem 'actionpack', '>= 5.0'
  within_files 'spec/controllers/**/*_spec.rb' do
    with_node node_type: 'send', receiver: nil, message: { in: %w[get post delete patch put] }, arguments: { size: { gt: 1 } } do
      case current_node.arguments.size
      when 4
        replace :arguments, with: '{{arguments.0}}, params: {{arguments.1}}, session: {{arguments.2}}, flash: {{arguments.3}}'
      when 3
        replace :arguments, with: '{{arguments.0}}, params: {{arguments.1}}, session: {{arguments.2}}'
      when 2
        replace :arguments, with: '{{arguments.0}}, params: {{arguments.1}}'
      end
    end
  end
end

Now we can use the updated snippet to search in our project.

And replace them all.

That’s all. I hope you found it informative and helpful. If you have any questions or feedback, please don’t hesitate to leave a comment below.