Question about runtime dependencies inside engines .gemspec file

[luccasmaso]

Hi,

The first step I'm trying to accomplish for now is just to have runtime dependencies shared by engines to be in one place. In order to do that, I've created a /gemfiles folder at root with *.gemfiles and then including them with eval_gemfile inside engines.

# gemfiles/http.gemfile

gem 'rest-client', '2.1.0'

# engines/authentication/Gemfile

source 'https://rubygems.org'

eval_gemfile '../../gemfiles/rails.gemfile'
eval_gemfile '../../gemfiles/http.gemfile'
...

The problem is that I need to require the rest-client at engines/authentication/lib/authentication.rb to make it available inside engine runtime:

require "authentication/version"
require "authentication/engine"

require "rest-client"

module Authentication
   ....
end

But, to make this work, I must define rest-client inside engine's .gemspec (spec.add_dependency). But if I do that, it looses the purpose of the eval_gemfile for sharing versions.

Sorry if I'm misunderstanding the concept.

Thanks.

[palkan]

I must define rest-client inside engine's .gemspec (spec.add_dependency). But if I do that, it looses the purpose of the eval_gemfile for sharing versions.

.gemspec is for requirements, not freezing versions; you may have a relaxed spec for rest-client in your .gemspec (e.g., ~> 2.0).

Do you use the shared lock file strategy?

[luccasmaso]

Hi, sorry about long time since I've posted this.

.gemspec is for requirements, not freezing versions; you may have a relaxed spec for rest-client in your .gemspec (e.g., ~> 2.0).

Right, I've now properly set dependencies with the shared lock file strategy. The application now starts and everything loads as expected!

The only issue I've struggling to resolve/understand is around testing (with rspec). I'm using the latest script version that you've updated from @maiksimov sample repo. As far as I undertood, each component declared in the root Gemfile with:

component 'my_component', namespace: "engines"

will dynamically create a group (group component_group do) with it's name. That way, dummy app from engine should be able to load only dependencies related by configuring Bundler.require(:my_component) inside /config/application.rb

The error I'm getting when running rspec command from engine is that I can't figure out the cause. If I run with *Rails.groups it loads everything but works.

Some things I didn't understand, that can be related:

• Why it has eval_gemfile and gem declarations in first two lines? https://github.com/palkan/test-rails-project/blob/main/engines/test-engine/Gemfile.dev
• Everytime I run rspec, a Gemfile.lock is generated inside the engine (I've configured /.bundle/config)

Appreciate with any help!

[palkan]

Why it has eval_gemfile and gem declarations in first two lines?

The first one defines where to find local deps; the second uses .gemspec to get the dependencies. Without the first line, Bundler wouldn't know how to satisfy local deps.

Everytime I run rspec, a Gemfile.lock is generated inside the engine (I've configured /.bundle/config)

Do you run it with bundle exec?

The error I'm getting when running rspec command

This error doesn't seem to relevant; it looks like spec_helper.rb (or rails_helper.rb) is loaded twice 'cause Rails app to be initialized twice, which leads to this exception.

Try to wrap require "<...>/environment" with begin; rescue; exit; end to see the actual error (see https://github.com/palkan/engems/blob/6b824b182676dedc10ba88ea3aa5764e36f40e14/examples/generators/engine/templates/spec/rails_helper.rb.tt#L15-L37).