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