100 lines
3.5 KiB
Ruby
100 lines
3.5 KiB
Ruby
module ActiveSupport
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# Backtraces often include many lines that are not relevant for the context under review. This makes it hard to find the
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# signal amongst the backtrace noise, and adds debugging time. With a BacktraceCleaner, filters and silencers are used to
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# remove the noisy lines, so that only the most relevant lines remain.
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#
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# Filters are used to modify lines of data, while silencers are used to remove lines entirely. The typical filter use case
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# is to remove lengthy path information from the start of each line, and view file paths relevant to the app directory
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# instead of the file system root. The typical silencer use case is to exclude the output of a noisy library from the
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# backtrace, so that you can focus on the rest.
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#
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# ==== Example:
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#
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# bc = BacktraceCleaner.new
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# bc.add_filter { |line| line.gsub(Rails.root, '') }
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# bc.add_silencer { |line| line =~ /mongrel|rubygems/ }
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# bc.clean(exception.backtrace) # will strip the Rails.root prefix and skip any lines from mongrel or rubygems
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#
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# To reconfigure an existing BacktraceCleaner (like the default one in Rails) and show as much data as possible, you can
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# always call <tt>BacktraceCleaner#remove_silencers!</tt>, which will restore the backtrace to a pristine state. If you
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# need to reconfigure an existing BacktraceCleaner so that it does not filter or modify the paths of any lines of the
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# backtrace, you can call BacktraceCleaner#remove_filters! These two methods will give you a completely untouched backtrace.
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#
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# Inspired by the Quiet Backtrace gem by Thoughtbot.
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class BacktraceCleaner
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def initialize
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@filters, @silencers = [], []
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end
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# Returns the backtrace after all filters and silencers have been run against it. Filters run first, then silencers.
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def clean(backtrace, kind = :silent)
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filtered = filter(backtrace)
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case kind
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when :silent
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silence(filtered)
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when :noise
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noise(filtered)
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else
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filtered
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end
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end
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# Adds a filter from the block provided. Each line in the backtrace will be mapped against this filter.
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#
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# Example:
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#
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# # Will turn "/my/rails/root/app/models/person.rb" into "/app/models/person.rb"
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# backtrace_cleaner.add_filter { |line| line.gsub(Rails.root, '') }
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def add_filter(&block)
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@filters << block
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end
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# Adds a silencer from the block provided. If the silencer returns true for a given line, it will be excluded from
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# the clean backtrace.
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#
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# Example:
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#
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# # Will reject all lines that include the word "mongrel", like "/gems/mongrel/server.rb" or "/app/my_mongrel_server/rb"
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# backtrace_cleaner.add_silencer { |line| line =~ /mongrel/ }
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def add_silencer(&block)
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@silencers << block
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end
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# Will remove all silencers, but leave in the filters. This is useful if your context of debugging suddenly expands as
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# you suspect a bug in one of the libraries you use.
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def remove_silencers!
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@silencers = []
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end
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def remove_filters!
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@filters = []
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end
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private
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def filter(backtrace)
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@filters.each do |f|
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backtrace = backtrace.map { |line| f.call(line) }
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end
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backtrace
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end
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def silence(backtrace)
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@silencers.each do |s|
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backtrace = backtrace.reject { |line| s.call(line) }
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end
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backtrace
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end
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def noise(backtrace)
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@silencers.each do |s|
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backtrace = backtrace.select { |line| s.call(line) }
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end
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backtrace
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end
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end
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end
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