2

Here is annoyance I have with strack traces in rails -- they print the error first which means to view any error, you have scroll up in your termanl to see what the error is.

is there a way by which the error & stracktrace can be printed in reverse order, so you can view the error without having to scroll. for example:

This is rails/ruby currently prints stracktraces:

      /activesupport/lib/active_support/dependencies.rb:228:in `require': cannot load such file -- pry (LoadError)
        from /activesupport/lib/active_support/dependencies.rb:228:in `block in require'
        from /activesupport/lib/active_support/dependencies.rb:213:in `load_dependency'
        from /activesupport/lib/active_support/dependencies.rb:228:in `require'
        from /actionpack/lib/action_dispatch/routing/mapper.rb:307:in `normalize_path'
        from /actionpack/lib/action_dispatch/routing/mapper.rb:79:in `normalize_path!'
        from /actionpack/lib/action_dispatch/routing/mapper.rb:65:in `initialize'
        from /actionpack/lib/action_dispatch/routing/mapper.rb:1429:in `new'
        from /actionpack/lib/action_dispatch/routing/mapper.rb:1429:in `add_route'
        from /actionpack/lib/action_dispatch/routing/mapper.rb:1408:in `decomposed_match'
        from /actionpack/lib/action_dispatch/routing/mapper.rb:1389:in `block in match'
        from /actionpack/lib/action_dispatch/routing/mapper.rb:1380:in `each'
        from /actionpack/lib/action_dispatch/routing/mapper.rb:1380:in `match'
        from /actionpack/lib/action_dispatch/routing/mapper.rb:502:in `mount'
        from /ruby-2.0.0-p0/bundler/gems/sprockets-rails-bbf755e8b3aa/lib/sprockets/railtie.rb:125:in `block (2 levels) in <class:Railtie>'
        from /actionpack/lib/action_dispatch/routing/route_set.rb:315:in `instance_exec'
        from /actionpack/lib/action_dispatch/routing/route_set.rb:315:in `eval_block'
        from /actionpack/lib/action_dispatch/routing/route_set.rb:330:in `block in clear!'
        from /actionpack/lib/action_dispatch/routing/route_set.rb:330:in `each'
        from /actionpack/lib/action_dispatch/routing/route_set.rb:330:in `clear!'
        from /railties/lib/rails/application/routes_reloader.rb:35:in `block in clear!'
        from /railties/lib/rails/application/routes_reloader.rb:33:in `each'
        from /railties/lib/rails/application/routes_reloader.rb:33:in `clear!'
        from /railties/lib/rails/application/routes_reloader.rb:15:in `reload!'
        from /railties/lib/rails/application/routes_reloader.rb:26:in `block in updater'
        from /activesupport/lib/active_support/file_update_checker.rb:75:in `call'
        from /activesupport/lib/active_support/file_update_checker.rb:75:in `execute'
        from /railties/lib/rails/application/routes_reloader.rb:27:in `updater'
        from /railties/lib/rails/application/routes_reloader.rb:7:in `execute_if_updated'
        from /railties/lib/rails/application/finisher.rb:69:in `block in <module:Finisher>'
        from /railties/lib/rails/initializable.rb:30:in `instance_exec'
        from /railties/lib/rails/initializable.rb:30:in `run'
        from /railties/lib/rails/initializable.rb:55:in `block in run_initializers'
        from ruby-2.0.0-p0/lib/ruby/2.0.0/tsort.rb:150:in `block in tsort_each'
        from ruby-2.0.0-p0/lib/ruby/2.0.0/tsort.rb:183:in `block (2 levels) in each_strongly_connected_component'
        from ruby-2.0.0-p0/lib/ruby/2.0.0/tsort.rb:219:in `each_strongly_connected_component_from'
        from ruby-2.0.0-p0/lib/ruby/2.0.0/tsort.rb:182:in `block in each_strongly_connected_component'
        from ruby-2.0.0-p0/lib/ruby/2.0.0/tsort.rb:180:in `each'
        from ruby-2.0.0-p0/lib/ruby/2.0.0/tsort.rb:180:in `each_strongly_connected_component'
        from ruby-2.0.0-p0/lib/ruby/2.0.0/tsort.rb:148:in `tsort_each'
        from /railties/lib/rails/initializable.rb:54:in `run_initializers'
        from /railties/lib/rails/application.rb:214:in `initialize!'
        from /railties/lib/rails/railtie/configurable.rb:30:in `method_missing'
        from /demo/config/environment.rb:5:in `<top (required)>'
        from /demo/config.ru:3:in `require'
        from /demo/config.ru:3:in `block in <main>'
        from /ruby-2.0.0-p0/gems/rack-1.5.2/lib/rack/builder.rb:55:in `instance_eval'
        from /ruby-2.0.0-p0/gems/rack-1.5.2/lib/rack/builder.rb:55:in `initialize'
        from /demo/config.ru:in `new'
        from /demo/config.ru:in `<main>'
        from /ruby-2.0.0-p0/gems/rack-1.5.2/lib/rack/builder.rb:49:in `eval'
        from /ruby-2.0.0-p0/gems/rack-1.5.2/lib/rack/builder.rb:49:in `new_from_string'
        from /ruby-2.0.0-p0/gems/rack-1.5.2/lib/rack/builder.rb:40:in `parse_file'
        from /ruby-2.0.0-p0/gems/rack-1.5.2/lib/rack/server.rb:277:in `build_app_and_options_from_config'
        from /ruby-2.0.0-p0/gems/rack-1.5.2/lib/rack/server.rb:199:in `app'
        from /railties/lib/rails/commands/server.rb:48:in `app'
        from /ruby-2.0.0-p0/gems/rack-1.5.2/lib/rack/server.rb:314:in `wrapped_app'
        from /railties/lib/rails/commands/server.rb:75:in `start'
        from /railties/lib/rails/commands.rb:80:in `block in <top (required)>'
        from /railties/lib/rails/commands.rb:75:in `tap'
        from /railties/lib/rails/commands.rb:75:in `<top (required)>'
        from bin/rails:4:in `require'
        from bin/rails:4:in `<main>'

Is there a way by which I can get this same stracktrace in reverse order, so I don't have to scroll my terminal everytime i get a error. something similar to this:

    from bin/rails:4:in `<main>'
    from bin/rails:4:in `require'
    from /railties/lib/rails/commands.rb:75:in `<top (required)>'
    from /railties/lib/rails/commands.rb:75:in `tap'
    from /railties/lib/rails/commands.rb:80:in `block in <top (required)>'
    from /railties/lib/rails/commands/server.rb:75:in `start'
    from /ruby-2.0.0-p0/gems/rack-1.5.2/lib/rack/server.rb:314:in `wrapped_app'
    from /railties/lib/rails/commands/server.rb:48:in `app'
    from /ruby-2.0.0-p0/gems/rack-1.5.2/lib/rack/server.rb:199:in `app'
    from /ruby-2.0.0-p0/gems/rack-1.5.2/lib/rack/server.rb:277:in `build_app_and_options_from_config'
    from /ruby-2.0.0-p0/gems/rack-1.5.2/lib/rack/builder.rb:40:in `parse_file'
    from /ruby-2.0.0-p0/gems/rack-1.5.2/lib/rack/builder.rb:49:in `new_from_string'
    from /ruby-2.0.0-p0/gems/rack-1.5.2/lib/rack/builder.rb:49:in `eval'
    from /demo/config.ru:in `<main>'
    from /demo/config.ru:in `new'
    from /ruby-2.0.0-p0/gems/rack-1.5.2/lib/rack/builder.rb:55:in `initialize'
    from /ruby-2.0.0-p0/gems/rack-1.5.2/lib/rack/builder.rb:55:in `instance_eval'
    from /demo/config.ru:3:in `block in <main>'
    from /demo/config.ru:3:in `require'
    from /demo/config/environment.rb:5:in `<top (required)>'
    from /railties/lib/rails/railtie/configurable.rb:30:in `method_missing'
    from /railties/lib/rails/application.rb:214:in `initialize!'
    from /railties/lib/rails/initializable.rb:54:in `run_initializers'
    from ruby-2.0.0-p0/lib/ruby/2.0.0/tsort.rb:148:in `tsort_each'
    from ruby-2.0.0-p0/lib/ruby/2.0.0/tsort.rb:180:in `each_strongly_connected_component'
    from ruby-2.0.0-p0/lib/ruby/2.0.0/tsort.rb:180:in `each'
    from ruby-2.0.0-p0/lib/ruby/2.0.0/tsort.rb:182:in `block in each_strongly_connected_component'
    from ruby-2.0.0-p0/lib/ruby/2.0.0/tsort.rb:219:in `each_strongly_connected_component_from'
    from ruby-2.0.0-p0/lib/ruby/2.0.0/tsort.rb:183:in `block (2 levels) in each_strongly_connected_component'
    from ruby-2.0.0-p0/lib/ruby/2.0.0/tsort.rb:150:in `block in tsort_each'
    from /railties/lib/rails/initializable.rb:55:in `block in run_initializers'
    from /railties/lib/rails/initializable.rb:30:in `run'
    from /railties/lib/rails/initializable.rb:30:in `instance_exec'
    from /railties/lib/rails/application/finisher.rb:69:in `block in <module:Finisher>'
    from /railties/lib/rails/application/routes_reloader.rb:7:in `execute_if_updated'
    from /railties/lib/rails/application/routes_reloader.rb:27:in `updater'
    from /activesupport/lib/active_support/file_update_checker.rb:75:in `execute'
    from /activesupport/lib/active_support/file_update_checker.rb:75:in `call'
    from /railties/lib/rails/application/routes_reloader.rb:26:in `block in updater'
    from /railties/lib/rails/application/routes_reloader.rb:15:in `reload!'
    from /railties/lib/rails/application/routes_reloader.rb:33:in `clear!'
    from /railties/lib/rails/application/routes_reloader.rb:33:in `each'
    from /railties/lib/rails/application/routes_reloader.rb:35:in `block in clear!'
    from /actionpack/lib/action_dispatch/routing/route_set.rb:330:in `clear!'
    from /actionpack/lib/action_dispatch/routing/route_set.rb:330:in `each'
    from /actionpack/lib/action_dispatch/routing/route_set.rb:330:in `block in clear!'
    from /actionpack/lib/action_dispatch/routing/route_set.rb:315:in `eval_block'
    from /actionpack/lib/action_dispatch/routing/route_set.rb:315:in `instance_exec'
    from /ruby-2.0.0-p0/bundler/gems/sprockets-rails-bbf755e8b3aa/lib/sprockets/railtie.rb:125:in `block (2 levels) in <class:Railtie>'
    from /actionpack/lib/action_dispatch/routing/mapper.rb:502:in `mount'
    from /actionpack/lib/action_dispatch/routing/mapper.rb:1380:in `match'
    from /actionpack/lib/action_dispatch/routing/mapper.rb:1380:in `each'
    from /actionpack/lib/action_dispatch/routing/mapper.rb:1389:in `block in match'
    from /actionpack/lib/action_dispatch/routing/mapper.rb:1408:in `decomposed_match'
    from /actionpack/lib/action_dispatch/routing/mapper.rb:1429:in `add_route'
    from /actionpack/lib/action_dispatch/routing/mapper.rb:1429:in `new'
    from /actionpack/lib/action_dispatch/routing/mapper.rb:65:in `initialize'
    from /actionpack/lib/action_dispatch/routing/mapper.rb:79:in `normalize_path!'
    from /actionpack/lib/action_dispatch/routing/mapper.rb:307:in `normalize_path'
    from /activesupport/lib/active_support/dependencies.rb:228:in `require'
    from /activesupport/lib/active_support/dependencies.rb:213:in `load_dependency'
    from /activesupport/lib/active_support/dependencies.rb:228:in `block in require'
  /activesupport/lib/active_support/dependencies.rb:228:in `require': cannot load such file -- pry (LoadError)

Possible?

CuriousMind
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  • Overriding `Exception#backtrace` caused `stack level too deep` & `illegal hardware instruction`. – Leventix Apr 24 '13 at 21:00
  • @Leventix You probably don't want to rescue from nor monkeypatch `Exception`. You probably want to rescue from `StandardError` instead. Here's why: http://stackoverflow.com/questions/10048173/why-is-it-bad-style-to-rescue-exception-e-in-ruby – Andrew Feb 20 '14 at 23:28

1 Answers1

2

There are several ways to do this.

If you're in irb, or the debugger something like:

caller.reverse

Will give you what you want. The alternative then is to wrap all your code like so

begin
  all the code
rescue StandardError => e 
  puts e.backtrace.reverse
end

And finally you could extend backtrace on Exception to print caller.reverse but extending core modules is not a great idea at all.

fnln
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  • You probably don't want to rescue from nor monkeypatch `Exception`. You probably want to rescue from `StandardError` instead. Here's why: http://stackoverflow.com/questions/10048173/why-is-it-bad-style-to-rescue-exception-e-in-ruby – Andrew Feb 20 '14 at 23:27