class Rack::ShowExceptions
Rack::ShowExceptions catches all exceptions raised from the app it wraps. It shows a useful backtrace with the sourcefile and clickable context, the whole Rack environment and the request data.
Be careful when you use this on public-facing sites as it could reveal information helpful to attackers.
Constants
- CONTEXT
Public Class Methods
new(app)
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# File lib/rack/showexceptions.rb, line 18 def initialize(app) @app = app @template = ERB.new(TEMPLATE) end
Public Instance Methods
call(env)
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# File lib/rack/showexceptions.rb, line 23 def call(env) @app.call(env) rescue StandardError, LoadError, SyntaxError => e exception_string = dump_exception(e) env["rack.errors"].puts(exception_string) env["rack.errors"].flush if prefers_plain_text?(env) content_type = "text/plain" body = [exception_string] else content_type = "text/html" body = pretty(env, e) end [500, {"Content-Type" => content_type, "Content-Length" => Rack::Utils.bytesize(body.join).to_s}, body] end
dump_exception(exception)
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# File lib/rack/showexceptions.rb, line 49 def dump_exception(exception) string = "#{exception.class}: #{exception.message}\n" string << exception.backtrace.map { |l| "\t#{l}" }.join("\n") string end
prefers_plain_text?(env)
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# File lib/rack/showexceptions.rb, line 45 def prefers_plain_text?(env) env["HTTP_X_REQUESTED_WITH"] == "XMLHttpRequest" && (!env["HTTP_ACCEPT"] || !env["HTTP_ACCEPT"].include?("text/html")) end
pretty(env, exception)
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# File lib/rack/showexceptions.rb, line 55 def pretty(env, exception) req = Rack::Request.new(env) # This double assignment is to prevent an "unused variable" warning on # Ruby 1.9.3. Yes, it is dumb, but I don't like Ruby yelling at me. path = path = (req.script_name + req.path_info).squeeze("/") # This double assignment is to prevent an "unused variable" warning on # Ruby 1.9.3. Yes, it is dumb, but I don't like Ruby yelling at me. frames = frames = exception.backtrace.map { |line| frame = OpenStruct.new if line =~ /(.*?):(\d+)(:in `(.*)')?/ frame.filename = $1 frame.lineno = $2.to_i frame.function = $4 begin lineno = frame.lineno-1 lines = ::File.readlines(frame.filename) frame.pre_context_lineno = [lineno-CONTEXT, 0].max frame.pre_context = lines[frame.pre_context_lineno...lineno] frame.context_line = lines[lineno].chomp frame.post_context_lineno = [lineno+CONTEXT, lines.size].min frame.post_context = lines[lineno+1..frame.post_context_lineno] rescue end frame else nil end }.compact [@template.result(binding)] end