Rails6: [WARNING] Could not load generator "generators/knock/install_generator".

[Yuhei Okazaki]

Please tell me what to do.

Steps to reproduce

1. Execute rails new sample_project --api .
2. Add gem 'knock' to Gemfile
3. Execute bundle install
4. Execute rails generate knock:install .

Expected behavior

config/initializers/knock.rb is created without errors.

Actual behavior

The following message is output.

[WARNING] Could not load generator "generators/knock/install_generator". Error: expected file /home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/knock-2.1.1/lib/generators/knock/install_generator.rb to define constant InstallGenerator, but didn't.
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/zeitwerk-2.1.9/lib/zeitwerk/loader/callbacks.rb:17:in `on_file_autoloaded'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/zeitwerk-2.1.9/lib/zeitwerk/kernel.rb:27:in `block in require'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/zeitwerk-2.1.9/lib/zeitwerk/kernel.rb:23:in `tap'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/zeitwerk-2.1.9/lib/zeitwerk/kernel.rb:23:in `require'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/railties-6.0.0/lib/rails/command/behavior.rb:44:in `block (2 levels) in lookup'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/railties-6.0.0/lib/rails/command/behavior.rb:40:in `each'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/railties-6.0.0/lib/rails/command/behavior.rb:40:in `block in lookup'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/railties-6.0.0/lib/rails/command/behavior.rb:39:in `each'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/railties-6.0.0/lib/rails/command/behavior.rb:39:in `lookup'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/railties-6.0.0/lib/rails/generators.rb:258:in `find_by_namespace'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/railties-6.0.0/lib/rails/generators.rb:274:in `invoke'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/railties-6.0.0/lib/rails/commands/generate/generate_command.rb:26:in `perform'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/thor-0.20.3/lib/thor/command.rb:27:in `run'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/thor-0.20.3/lib/thor/invocation.rb:126:in `invoke_command'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/thor-0.20.3/lib/thor.rb:387:in `dispatch'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/railties-6.0.0/lib/rails/command/base.rb:65:in `perform'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/railties-6.0.0/lib/rails/command.rb:46:in `invoke'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/railties-6.0.0/lib/rails/commands.rb:18:in `<main>'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `require'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:22:in `block in require_with_bootsnap_lfi'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/loaded_features_index.rb:92:in `register'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:21:in `require_with_bootsnap_lfi'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:30:in `require'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/zeitwerk-2.1.9/lib/zeitwerk/kernel.rb:23:in `require'
/home/user/Documents/develop/knock_test/bin/rails:9:in `<main>'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:54:in `load'
/home/user/.rbenv/versions/2.6.3/lib/ruby/gems/2.6.0/gems/bootsnap-1.4.4/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:54:in `load'
/home/user/.rbenv/versions/2.6.3/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
/home/user/.rbenv/versions/2.6.3/lib/ruby/2.6.0/rubygems/core_ext/kernel_require.rb:54:in `require'
-e:1:in `<main>'
      create  config/initializers/knock.rb

System configuration

Rails version: 6.0.0

Ruby version: 2.6.3p62

[Yuhei Okazaki]

When the following is added to application.rb, the error is no longer output.

config.load_defaults 6.0 and config.autoloader = :classic

[Yuhei Okazaki]

I understood this problem causes by zeitwerk that is rails6 autoloader.
I close this issue.
rails/rails#36381

[activeliang]

thx~