Class: Rack::ShowExceptions

### Home Classes Methods

### In Files

- lib/rack/showexceptions.rb

### Parent

Object

### Methods

- ::new
- #call
- #pretty

### Files

- KNOWN-ISSUES
- README
- SPEC

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No matching classes.

# 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) click to toggle source

    # File lib/rack/showexceptions.rb, line 18
    def initialize(app)
      @app = app
      @template = ERB.new(TEMPLATE)
    end

### Public Instance Methods

call(env) click to toggle source

    # File lib/rack/showexceptions.rb, line 23
    def call(env)
      @app.call(env)
    rescue StandardError, LoadError, SyntaxError => e
      backtrace = pretty(env, e)
      [500,
       {"Content-Type" => "text/html",
        "Content-Length" => backtrace.join.size.to_s},
       backtrace]
    end

pretty(env, exception) click to toggle source

    # File lib/rack/showexceptions.rb, line 33
    def pretty(env, exception)
      req = Rack::Request.new(env)
      path = (req.script_name + req.path_info).squeeze("/")

      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

      env["rack.errors"].puts "#{exception.class}: #{exception.message}"
      env["rack.errors"].puts exception.backtrace.map { |l| "\t" + l }
      env["rack.errors"].flush

      [@template.result(binding)]
    end

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