Backtrace Silencer not working

Question

In my Rails app, I have set up the following backtrace silencer, as suggested by Michael Hartl in his Rails tutorial:

Rails.backtrace_cleaner.add_silencer { |line| line =~ /rvm/ }

But still I get all the noise I intended to filter out:

7:13:55 - INFO - Running: test/controllers/tags_controller_test.rb
Started

ERROR["test_should_get_index", TagsControllerTest, 0.45206]
test_should_get_index#TagsControllerTest (0.45s)
ActionController::UrlGenerationError:               
ActionController::UrlGenerationError: No route matches {:action=>"index", :controller=>"tags"}
        /Users/chris/.rvm/gems/ruby-2.0.0-p353/gems/actionpack-4.1.6/lib/action_dispatch/journey/formatter.rb:39:in `generate'
        /Users/chris/.rvm/gems/ruby-2.0.0-p353/gems/actionpack-4.1.6/lib/action_dispatch/routing/route_set.rb:599:in `generate'

Clearly the string "rvm" is present in the last two lines. But still they show up. Changing the string to ".rvm" didn't make any difference.

Answer 1

This is because of https://github.com/vipulnsward/rails/blob/ecc8f283cfc1b002b5141c527a827e74b770f2f0/actionpack/lib/action_dispatch/middleware/debug_exceptions.rb#L155-L156

Since application_trace is empty(This is because error is not from user code but route error), we are falling back to framework_trace, which does not filter it (it filters only noise).

You can solve it with creating your own log_formatter. In your development.rb and/or test.rb add

config.log_formatter = SilentLogger.new
config.log_formatter.add_silencer { |line| line =~ /rvm/ }

And create simple class in models with only method call required. There you can modify your backtrace as you wish.

class SilentLogger
  def initialize
    @silencers = []
  end

  def add_silencer(&block)
    @silencers << block
  end

  def call(severity, timestamp, progname, msg)
    backtrace = (String === msg) ? "#{msg}\n" : "#{msg.inspect}\n"

    return backtrace if @silencers.empty?

    @silencers.each do |s|
      backtrace = backtrace.split("\n").delete_if { |line| s.call(line) }
    end

    backtrace.join("\n")
  end
end