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| /puma|rubygems/.match?(line) } # 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.
Constants
- FORMATTED_GEMS_PATTERN
Public Class Methods
Source
# File lib/active_support/backtrace_cleaner.rb, line 32 def initialize @filters, @silencers = [], [] add_gem_filter add_gem_silencer add_stdlib_silencer end
Public Instance Methods
Source
# File lib/active_support/backtrace_cleaner.rb, line 60 def add_filter(&block) @filters << block end
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, '') }
Source
# File lib/active_support/backtrace_cleaner.rb, line 69 def add_silencer(&block) @silencers << 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| /puma/.match?(line) }
Source
# File lib/active_support/backtrace_cleaner.rb, line 41 def clean(backtrace, kind = :silent) filtered = filter_backtrace(backtrace) case kind when :silent silence(filtered) when :noise noise(filtered) else filtered end end
Returns the backtrace after all filters and silencers have been run against it. Filters run first, then silencers.
Source
# File lib/active_support/backtrace_cleaner.rb, line 83 def remove_filters! @filters = [] 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.
Source
# File lib/active_support/backtrace_cleaner.rb, line 76 def remove_silencers! @silencers = [] 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.
Private Instance Methods
Source
# File lib/active_support/backtrace_cleaner.rb, line 90 def add_gem_filter gems_paths = (Gem.path | [Gem.default_dir]).map { |p| Regexp.escape(p) } return if gems_paths.empty? gems_regexp = %r{\A(#{gems_paths.join('|')})/(bundler/)?gems/([^/]+)-([\w.]+)/(.*)} gems_result = '\3 (\4) \5' add_filter { |line| line.sub(gems_regexp, gems_result) } end
Source
# File lib/active_support/backtrace_cleaner.rb, line 99 def add_gem_silencer add_silencer { |line| FORMATTED_GEMS_PATTERN.match?(line) } end
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# File lib/active_support/backtrace_cleaner.rb, line 103 def add_stdlib_silencer add_silencer { |line| line.start_with?(RbConfig::CONFIG["rubylibdir"]) } end
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# File lib/active_support/backtrace_cleaner.rb, line 107 def filter_backtrace(backtrace) @filters.each do |f| backtrace = backtrace.map { |line| f.call(line) } end backtrace end
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# File lib/active_support/backtrace_cleaner.rb, line 123 def noise(backtrace) backtrace.select do |line| @silencers.any? do |s| s.call(line) end end end
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# File lib/active_support/backtrace_cleaner.rb, line 115 def silence(backtrace) @silencers.each do |s| backtrace = backtrace.reject { |line| s.call(line) } end backtrace end