Errors in controller class definitions are not surfaced

[frantic]

Steps to reproduce

Create a new Rails controller

class IndexController < ApplicationController
  call_to_a_function_that_does_not_exist

  def index
    puts "we are here"
  end
end

and register a route for it

# routes.rb
get "/", to: 'index#index'

Expected behavior

I'd expect to see and error like this in logs or webpage

NameError: undefined local variable or method `call_to_a_function_that_does_not_exist' for IndexController:Class

Actual behavior

If views/index/index.erb.html exists, Rails displays that view (but clearly isn't executing our index method, "we are here" is not in logs). Otherwise it shows an error that says "The action 'index' could not be found for IndexController".

System configuration

Rails version: 6.0.2.1

Ruby version: 2.6.5p114 (2019-10-01 revision 67812) [x86_64-linux]

[eugeneius]

This problem was originally reported in #35453 and #37650 and fixed in #37834, but the fix hasn't been released yet.

I've opened #38061 to backport the fix to the 6-0-stable branch.

[frantic]

Thanks @eugeneius!