ActiveSupport::BacktraceCleaner

Many backtraces include too much information that’s not relevant for the context. This makes it hard to find the signal in the backtrace and adds debugging time. With a BacktraceCleaner, you can setup filters and silencers for your particular context, so only the relevant lines are included.

If you need to reconfigure an existing BacktraceCleaner, like the one in Rails, to show as much as possible, you can always call BacktraceCleaner#remove_silencers! Also, 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 BacktraceCleaner#remove_filters! These two methods will give you a completely untouched backtrace.

Example:

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

Inspired by the Quiet Backtrace gem by Thoughtbot.

Public Class Methods

new() click to toggle source

    # File lib/active_support/backtrace_cleaner.rb, line 20
20:     def initialize
21:       @filters, @silencers = [], []
22:     end

Public Instance Methods

add_filter(&block) click to toggle source

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

Example:

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

    # File lib/active_support/backtrace_cleaner.rb, line 44
44:     def add_filter(&block)
45:       @filters << block
46:     end

add_silencer(&block) click to toggle source

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

Example:

  # 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/ }

    # File lib/active_support/backtrace_cleaner.rb, line 55
55:     def add_silencer(&block)
56:       @silencers << block
57:     end

clean(backtrace, kind = :silent) click to toggle source

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

    # File lib/active_support/backtrace_cleaner.rb, line 25
25:     def clean(backtrace, kind = :silent)
26:       filtered = filter(backtrace)
27: 
28:       case kind
29:       when :silent
30:         silence(filtered)
31:       when :noise
32:         noise(filtered)
33:       else
34:         filtered
35:       end
36:     end

remove_filters!() click to toggle source

    # File lib/active_support/backtrace_cleaner.rb, line 65
65:     def remove_filters!
66:       @filters = []
67:     end

remove_silencers!() click to toggle source

Will remove all silencers, but leave in the filters. This is useful if your context of debugging suddenly expands as you suspect a bug in the libraries you use.

    # File lib/active_support/backtrace_cleaner.rb, line 61
61:     def remove_silencers!
62:       @silencers = []
63:     end

Private Instance Methods

filter(backtrace) click to toggle source

    # File lib/active_support/backtrace_cleaner.rb, line 70
70:       def filter(backtrace)
71:         @filters.each do |f|
72:           backtrace = backtrace.map { |line| f.call(line) }
73:         end
74: 
75:         backtrace
76:       end

noise(backtrace) click to toggle source

    # File lib/active_support/backtrace_cleaner.rb, line 86
86:       def noise(backtrace)
87:         @silencers.each do |s|
88:           backtrace = backtrace.select { |line| s.call(line) }
89:         end
90: 
91:         backtrace
92:       end

silence(backtrace) click to toggle source

    # File lib/active_support/backtrace_cleaner.rb, line 78
78:       def silence(backtrace)
79:         @silencers.each do |s|
80:           backtrace = backtrace.reject { |line| s.call(line) }
81:         end
82: 
83:         backtrace
84:       end

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