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Class: ActiveSupport::BacktraceCleaner

Relationships & Source Files
Extension / Inclusion / Inheritance Descendants
Subclasses:
Rails::BacktraceCleaner
Inherits: Object
Defined in: activesupport/lib/active_support/backtrace_cleaner.rb

Overview

Backtraces often include many lines that are not relevant for the context under review. This makes it hard to find the signal amongst the backtrace noise, and adds debugging time. With a BacktraceCleaner, filters and silencers are used to remove the noisy lines, so that only the most relevant lines remain.

Filters are used to modify lines of data, while silencers are used to remove lines entirely. The typical filter use case is to remove lengthy path information from the start of each line, and view file paths relevant to the app directory instead of the file system root. The typical silencer use case is to exclude the output of a noisy library from the backtrace, so that you can focus on the rest.

bc = BacktraceCleaner.new
bc.add_filter   { |line| line.gsub(Rails.root.to_s, '') } # strip the Rails.root prefix
bc.add_silencer { |line| line =~ /mongrel|rubygems/ } # skip any lines from mongrel or rubygems
bc.clean(exception.backtrace) # perform the cleanup

To reconfigure an existing BacktraceCleaner (like the default one in ::Rails) and show as much data as possible, you can always call #remove_silencers!, which will restore the backtrace to a pristine state. If you need to reconfigure an existing BacktraceCleaner so that it does not filter or modify the paths of any lines of the backtrace, you can call #remove_filters! These two methods will give you a completely untouched backtrace.

Inspired by the Quiet Backtrace gem by Thoughtbot.

Class Method Summary

Instance Method Summary

Constructor Details

.new ⇒ BacktraceCleaner

[ GitHub ] 

  


# File 'activesupport/lib/active_support/backtrace_cleaner.rb', line 30



def initialize
  @filters, @silencers = [], []
end


  







Instance Method Details



  

    #add_filter(&block)  
  



  

    

Adds a filter from the block provided. Each line in the backtrace will be mapped against this filter.



# Will turn "/my/rails/root/app/models/person.rb" into "/app/models/person.rb"
backtrace_cleaner.add_filter { |line| line.gsub(Rails.root, '') }


  



  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/backtrace_cleaner.rb', line 55



def add_filter(&block)
  @filters << block
end


  








  

    #add_silencer(&block)  
  



  

    

Adds a silencer from the block provided. If the silencer returns true for a given line, it will be excluded from the clean backtrace.



# Will reject all lines that include the word "mongrel", like "/gems/mongrel/server.rb" or "/app/my_mongrel_server/rb"
backtrace_cleaner.add_silencer { |line| line =~ /mongrel/ }


  



  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/backtrace_cleaner.rb', line 64



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


  








  

    #clean(backtrace, kind = :silent)  
    Also known as: #filter
  



  

    

Returns the backtrace after all filters and silencers have been run against it. Filters run first, then silencers.


  



  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/backtrace_cleaner.rb', line 36



def clean(backtrace, kind = :silent)
  filtered = filter_backtrace(backtrace)

  case kind
  when :silent
    silence(filtered)
  when :noise
    noise(filtered)
  else
    filtered
  end
end


  








  

    #filter(backtrace, kind = :silent)  
  



  

    

Alias for #clean.


  



  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/backtrace_cleaner.rb', line 48



alias :filter :clean


  








  

    #remove_filters!  
  



  

    

Removes all filters, but leaves in the silencers. Useful if you suddenly need to see entire filepaths in the backtrace that you had already filtered out.


  



  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/backtrace_cleaner.rb', line 78



def remove_filters!
  @filters = []
end


  








  

    #remove_silencers!  
  



  

    

Removes all silencers, but leaves in the filters. Useful if your context of debugging suddenly expands as you suspect a bug in one of the libraries you use.


  



  [ GitHub ]


  

  


# File 'activesupport/lib/active_support/backtrace_cleaner.rb', line 71



def remove_silencers!
  @silencers = []
end