class ActiveSupport::BacktraceCleaner
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 = ActiveSupport::BacktraceCleaner.new bc.add_filter { |line| line.gsub(Rails.root.to_s, '') } # strip the Rails.root prefix bc.add_silencer { |line| line =~ /puma|rubygems/ } # skip any lines from puma 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
BacktraceCleaner#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
BacktraceCleaner#remove_filters!
These two methods will give
you a completely untouched backtrace.
Inspired by the Quiet Backtrace gem by thoughtbot.
Public Class Methods
# File lib/active_support/backtrace_cleaner.rb, line 32 def initialize @filters, @silencers = [], [] end
Public Instance Methods
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, '') }
# File lib/active_support/backtrace_cleaner.rb, line 57 def add_filter(&block) @filters << block end
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 "puma", like "/gems/puma/server.rb" or "/app/my_puma_server/rb" backtrace_cleaner.add_silencer { |line| line =~ /puma/ }
# File lib/active_support/backtrace_cleaner.rb, line 66 def add_silencer(&block) @silencers << block end
Returns the backtrace after all filters and silencers have been run against it. Filters run first, then silencers.
# File lib/active_support/backtrace_cleaner.rb, line 38 def clean(backtrace, kind = :silent) filtered = filter_backtrace(backtrace) case kind when :silent silence(filtered) when :noise noise(filtered) else filtered end end
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.
# File lib/active_support/backtrace_cleaner.rb, line 80 def remove_filters! @filters = [] end
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.
# File lib/active_support/backtrace_cleaner.rb, line 73 def remove_silencers! @silencers = [] end
Private Instance Methods
# File lib/active_support/backtrace_cleaner.rb, line 85 def filter_backtrace(backtrace) @filters.each do |f| backtrace = backtrace.map { |line| f.call(line) } end backtrace end
# File lib/active_support/backtrace_cleaner.rb, line 101 def noise(backtrace) backtrace - silence(backtrace) end
# File lib/active_support/backtrace_cleaner.rb, line 93 def silence(backtrace) @silencers.each do |s| backtrace = backtrace.reject { |line| s.call(line) } end backtrace end