Running application without RubyGems/Bundler

[voxik]

Bundler is on step away from being perfect and that would be when Bundler (and RubyGems) was completely from the application runtime.

Lets say we have this simple Rails Gemfile:

source 'https://rubygems.org'

ruby '3.0.0'

# Bundle edge Rails instead: gem 'rails', github: 'rails/rails', branch: 'main'
gem 'rails', '~> 6.1.2', '>= 6.1.2.1'
# Use sqlite3 as the database for Active Record
gem 'sqlite3', '~> 1.4'
# Use Puma as the app server
gem 'puma'

This transforms into Gemfile.lock:

GEM
  remote: https://rubygems.org/
  specs:
    actioncable (6.1.2.1)
      actionpack (= 6.1.2.1)
      activesupport (= 6.1.2.1)
      nio4r (~> 2.0)
      websocket-driver (>= 0.6.1)

... snip ...

PLATFORMS
  x86_64-linux

DEPENDENCIES
  puma
  rails (~> 6.1.2, >= 6.1.2.1)
  sqlite3 (~> 1.4)

RUBY VERSION
   ruby 3.0.0p0

BUNDLED WITH
   2.2.3

But what is really needed for application runtime? Just properly initialized $LOAD_PATH. So the Gemfile.lock above could be transformed into lets say Gemfile.rb:

$LOAD_PATH.unshift('/usr/share/gems/gems/actioncable-6.1.2.1/lib')
$LOAD_PATH.unshift('/usr/share/gems/gems/actionpack-6.1.2.1/lib')
$LOAD_PATH.unshift('/usr/share/gems/gems/activesupport-6.1.2.1/lib')

... snip ...

and Bundler also preloads the libraries by default, so there could also be:

requires 'action_cable'
requires 'action_pack'
requires 'active_support'

... snip ...

This way, one could run the application later via e.g. RUBYOPT="--disable-gems -r./Gemfile.rb rails server"

[deivid-rodriguez]

Bundler already has this feature, through bundle install --standalone.

[voxik]

It sounds it might do what I proposed, but except of it, it does way more which prevents it use. Let me explain.

I have generated the application using system installed Ruby on Rails, therefore I have every required gem available on the system. I can do the following:

$ bundle install --local
Resolving dependencies...
Using rake 13.0.3

... snip ...

Bundle complete! 3 Gemfile dependencies, 44 gems now installed.
Use `bundle info [gemname]` to see where a bundled gem is installed.

But the --standalone fails:

$ bundle install --local --standalone
Could not find rake-13.0.3 in any of the sources

Apparently, tries to do something unexpected. I don't want this feature to install anything. But maybe, I should rather report this as a bug against Bundler.