import DSL method removed without replacement?

[bclennox]

Steps to reproduce

In v3.6.0, the DSL supported an import method to load another config file within a given file. We use this to have a default.rb that gets loaded into each of our environments, which have environment-specific config in development.rb, production.rb, etc.

This method was removed in #1234 without any obvious explanation. There is a load method, but that doesn't load the file immediately (or at all?) the way that import does:

# config/puma/development.rb
load 'default'
puts 'Should not get here'

# config/puma/default.rb
raise 'Raising from default.rb'

$ bundle exec puma -e development
Should not get here
Puma starting in single mode...
# ...

With import instead of load:

# config/puma/development.rb
import 'default'
puts 'Should not get here'

# config/puma/default.rb
raise 'Raising from default.rb'

$ bundle exec puma -e development
RuntimeError: Raising from default.rb
  config/puma/default.rb:1:in `_load_from'
  /Users/brandan/repos/baseline/vendor/bundle/ruby/2.5.0/gems/puma-3.6.0/lib/puma/dsl.rb:26:in `instance_eval'
  /Users/brandan/repos/baseline/vendor/bundle/ruby/2.5.0/gems/puma-3.6.0/lib/puma/dsl.rb:26:in `_load_from'
  /Users/brandan/repos/baseline/vendor/bundle/ruby/2.5.0/gems/puma-3.6.0/lib/puma/dsl.rb:70:in `import'
  config/puma/development.rb:1:in `_load_from'
  /Users/brandan/repos/baseline/vendor/bundle/ruby/2.5.0/gems/puma-3.6.0/lib/puma/dsl.rb:26:in `instance_eval'
  /Users/brandan/repos/baseline/vendor/bundle/ruby/2.5.0/gems/puma-3.6.0/lib/puma/dsl.rb:26:in `_load_from'
  /Users/brandan/repos/baseline/vendor/bundle/ruby/2.5.0/gems/puma-3.6.0/lib/puma/dsl.rb:9:in `load'
  /Users/brandan/repos/baseline/vendor/bundle/ruby/2.5.0/gems/puma-3.6.0/lib/puma/configuration.rb:205:in `block in load'
  /Users/brandan/repos/baseline/vendor/bundle/ruby/2.5.0/gems/puma-3.6.0/lib/puma/configuration.rb:202:in `each'
  /Users/brandan/repos/baseline/vendor/bundle/ruby/2.5.0/gems/puma-3.6.0/lib/puma/configuration.rb:202:in `load'
  /Users/brandan/repos/baseline/vendor/bundle/ruby/2.5.0/gems/puma-3.6.0/lib/puma/launcher.rb:62:in `initialize'
  /Users/brandan/repos/baseline/vendor/bundle/ruby/2.5.0/gems/puma-3.6.0/lib/puma/cli.rb:65:in `new'
  /Users/brandan/repos/baseline/vendor/bundle/ruby/2.5.0/gems/puma-3.6.0/lib/puma/cli.rb:65:in `initialize'
  /Users/brandan/repos/baseline/vendor/bundle/ruby/2.5.0/gems/puma-3.6.0/bin/puma:8:in `new'
  /Users/brandan/repos/baseline/vendor/bundle/ruby/2.5.0/gems/puma-3.6.0/bin/puma:8:in `<top (required)>'
  /Users/brandan/repos/baseline/vendor/bundle/ruby/2.5.0/bin/puma:23:in `load'
  /Users/brandan/repos/baseline/vendor/bundle/ruby/2.5.0/bin/puma:23:in `<top (required)>'

According to the docs in the source, we would have to call Configuration#load at some point, but I'm not sure how or when to do that, since we're not explicitly creating a Configuration.

Expected behavior

I expected that import would still be supported when upgrading to v3.12.0, but since it's been over a year since it was removed and it doesn't seem to be affecting others (based on searching issues here), is there a different pattern that we should be following? Is there a way to make load work the way import worked?

Actual behavior

The "loaded" file does not seem to be loaded at all.

System configuration

Ruby version: 2.5.1
Rails version: 5.2.1
Puma version: 3.12.0

[bclennox]

I should note that _load_from appears to work the same as import if you pass it an absolute path:

# config/puma/development.rb
_load_from File.join(__dir__, 'default.rb')
puts 'Should not get here'

# config/puma/default.rb
raise 'Raising from default.rb'

$ bundle exec puma -e development
RuntimeError: Raising from default.rb
  config/puma/default.rb:1:in `_load_from'
  # ...

[nateberkopec]

I believe we'd like you to use the new system introduced in #1234 instead. Not really SemVer there so sorry about that. Is there a reason you can't do that?

[bclennox]

We were able to consolidate back to a single config file in config/puma.rb. Thanks!