Added ActiveSupport::BacktraceCleaner and Rails::BacktraceCleaner for cutting down on backtrace noise (inspired by the Thoughtbot Quiet Backtrace plugin) [DHH]

1 files changed, 72 insertions, 0 deletions

diff --git a/activesupport/lib/active_support/backtrace_cleaner.rb b/activesupport/lib/active_support/backtrace_cleaner.rb
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+++ b/activesupport/lib/active_support/backtrace_cleaner.rb
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+module ActiveSupport
+  # 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!
+  #
+  # 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.
+  class BacktraceCleaner
+    def initialize
+      @filters, @silencers = [], []
+    end
+    
+    # Returns the backtrace after all filters and silencers has been run against it. Filters run first, then silencers.
+    def clean(backtrace)
+      silence(filter(backtrace))
+    end
+
+    # 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, '') }
+    def add_filter(&block)
+      @filters << block
+    end
+
+    # 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/ }
+    def add_silencer(&block)
+      @silencers << block
+    end
+
+    # 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.
+    def remove_silencers!
+      @silencers = []
+    end
+
+    
+    private
+      def filter(backtrace)
+        @filters.each do |f|
+          backtrace = backtrace.map { |line| f.call(line) }
+        end
+        
+        backtrace
+      end
+      
+      def silence(backtrace)
+        @silencers.each do |s|
+          backtrace = backtrace.reject { |line| s.call(line) }
+        end
+        
+        backtrace
+      end
+  end
+end