This script replicates a weird bug in mruby

mruby-bug.rb

#!/usr/bin/env mruby

# Dataset, Container and self.dataset are a minimal set of prerequisites that 
# we extrapolated from our application, in order to replicate the bug
class Container
  attr_accessor :key_converter, :match
  attr_reader   :hsh

  def initialize
    @hsh= Hash.new
  end

  def method_missing(name, *args, &block)
    if name.to_s[-1] == '=' then
      key = name.to_s.chop.to_sym
      @hsh[key.to_sym] = args.first
    else
      return @hsh[name.to_sym]
    end
  rescue => e
    puts "Got: #{name}(#{args})"
    puts "content: #{@hsh}"
    raise e
  end

end

class Dataset
  @@content = Container.new 
  def self.content; @@content; end
  def self.content=(v); @@content = v; end
end 

def self.dataset
  yield Dataset.content
end


# Uncomment this dummy line and it breaks at key :initial_alpha in
# data.BoundaryConditions
# Comment it, and it works
a = ''
# Also, comment at least one line in data.Parameters and it runs


dataset do |data|

  data.InfoLevel = 4
  
  data.Solver = {
    :max_iter  => 300,  
    :tolerance => 1e-9,
  }
  
  data.BoundaryConditions = {
    :initial_n       => 0,
    :initial_alpha   => 0,
    :initial_u       => 0,
    :initial_v       => 0,
    :initial_z       => 0,
    :initial_phi     => 0,
    :initial_mu      => 0,
    :initial_Omega   => 0,
    :initial_omega_r => 0,
    :initial_z_dot   => 0,
    :initial_phi_dot => 0,
    :initial_mu_dot  => 0,
    :initial_as      => 0,
    :initial_delta   => 0,
    :final_n         => 0,
    :final_alpha     => 0,
    :final_u         => 0,
    :final_v         => 0,
    :final_z         => 0,
    :final_phi       => 0,
    :final_mu        => 0,
    :final_Omega     => 0,
    :final_omega_r   => 0,
    :final_z_dot     => 0,
    :final_phi_dot   => 0,
    :final_mu_dot    => 0,
    :final_as        => 0,
    :final_delta     => 0
  }

  data.Parameters = {
    :C_dA       => 0.50,
    :I_r        => 1,
    :I_xx       => 23.82,
    :I_yy       => 20.21,
    :I_zz       => 26.40,
    :KL_f       => 16.0,
    :KL_r       => 28.0,
    :KS_r       => 20.0,
    :Pmax       => 0.200e6,
    :a          => 0.4,
    :b          => 0.4,
    :c_f        => 0.5e3,
    :c_r        => 0.5e3,
    :g          => 9.81,
    :h          => 0.26,
    :k_f        => 0.10e5,
    :k_r        => 0.10e5,
    :m          => 165.0,
    :r_r        => 0,
    :rho        => 1.2,
    :t_f        => 1.055,
    :t_r        => 1.2,
    :u0         => 0,
    :wET        => 1,
    :wPL        => 0,
    :wn         => 0,
    :friction   => 1,
    :kappa_max  => 0.5e-1,
    :lambda_max => 0.1,
    :min_speed  => 5,
    :Omega_f    => 0,
    :Omega_i    => 0,
    :alpha_f    => 0,
    :alpha_i    => 0,
    :as_f       => 0,
    :as_i       => 0,
    :delta_f    => 0,
    :delta_i    => 0,
    :mu_f       => 0,
    :mu_i       => 0,
    :n_f        => 0,
    :n_i        => 0,
    :phi_f      => 0,
    :phi_i      => 0,
    :u_f        => 0,
    :u_i        => 0,
    :v_f        => 0,
    :v_i        => 0,
    :z_dot_f    => 0,
    :z_dot_i    => 0,
    :z_f        => 0,
    :z_i        => 0,
    :mu_dot_f   => 0,
    :mu_dot_i   => 0,
    :omega_r_f  => 0,
    :omega_r_i  => 0,
    :phi_dot_f  => 0,
    :phi_dot_i  => 0,
    :posReg_h   => 0.1e-1
  }


end

p Dataset.content