module Sprockets::Server

`Server` is a concern mixed into `Environment` and `Index` that provides a Rack compatible `call` interface and url generation helpers.

Public Instance Methods

call(env) click to toggle source

`call` implements the Rack 1.x specification which accepts an `env` Hash and returns a three item tuple with the status code, headers, and body.

Mapping your environment at a url prefix will serve all assets in the path.

map "/assets" do
  run Sprockets::Environment.new
end

A request for `“/assets/foo/bar.js”` will search your environment for `“foo/bar.js”`.

# File lib/sprockets/server.rb, line 22
def call(env)
  start_time = Time.now.to_f
  time_elapsed = lambda { ((Time.now.to_f - start_time) * 1000).to_i }

  msg = "Served asset #{env['PATH_INFO']} -"

  # Mark session as "skipped" so no `Set-Cookie` header is set
  env['rack.session.options'] ||= {}
  env['rack.session.options'][:defer] = true
  env['rack.session.options'][:skip] = true

  # Extract the path from everything after the leading slash
  path = unescape(env['PATH_INFO'].to_s.sub(/^\//, ''))

  # Strip fingerprint
  if fingerprint = path_fingerprint(path)
    path = path.sub("-#{fingerprint}", '')
  end

  # URLs containing a `".."` are rejected for security reasons.
  if forbidden_request?(path)
    return forbidden_response
  end

  # Look up the asset.
  asset = find_asset(path, :bundle => !body_only?(env))

  # `find_asset` returns nil if the asset doesn't exist
  if asset.nil?
    logger.info "#{msg} 404 Not Found (#{time_elapsed.call}ms)"

    # Return a 404 Not Found
    not_found_response

  # Check request headers `HTTP_IF_NONE_MATCH` against the asset digest
  elsif etag_match?(asset, env)
    logger.info "#{msg} 304 Not Modified (#{time_elapsed.call}ms)"

    # Return a 304 Not Modified
    not_modified_response(asset, env)

  else
    logger.info "#{msg} 200 OK (#{time_elapsed.call}ms)"

    # Return a 200 with the asset contents
    ok_response(asset, env)
  end
rescue Exception => e
  logger.error "Error compiling asset #{path}:"
  logger.error "#{e.class.name}: #{e.message}"

  case content_type_of(path)
  when "application/javascript"
    # Re-throw JavaScript asset exceptions to the browser
    logger.info "#{msg} 500 Internal Server Error\n\n"
    return javascript_exception_response(e)
  when "text/css"
    # Display CSS asset exceptions in the browser
    logger.info "#{msg} 500 Internal Server Error\n\n"
    return css_exception_response(e)
  else
    raise
  end
end

Private Instance Methods

body_only?(env) click to toggle source

Test if `?body=1` or `body=true` query param is set

# File lib/sprockets/server.rb, line 182
def body_only?(env)
  env["QUERY_STRING"].to_s =~ /body=(1|t)/
end
css_exception_response(exception) click to toggle source

Returns a CSS response that hides all elements on the page and displays the exception

# File lib/sprockets/server.rb, line 116
def css_exception_response(exception)
  message   = "\n#{exception.class.name}: #{exception.message}"
  backtrace = "\n  #{exception.backtrace.first}"

  body = <<-CSS
    html {
      padding: 18px 36px;
    }

    head {
      display: block;
    }

    body {
      margin: 0;
      padding: 0;
    }

    body > * {
      display: none !important;
    }

    head:after, body:before, body:after {
      display: block !important;
    }

    head:after {
      font-family: sans-serif;
      font-size: large;
      font-weight: bold;
      content: "Error compiling CSS asset";
    }

    body:before, body:after {
      font-family: monospace;
      white-space: pre-wrap;
    }

    body:before {
      font-weight: bold;
      content: "#{escape_css_content(message)}";
    }

    body:after {
      content: "#{escape_css_content(backtrace)}";
    }
  CSS

  [ 200, { "Content-Type" => "text/css;charset=utf-8", "Content-Length" => Rack::Utils.bytesize(body).to_s }, [ body ] ]
end
escape_css_content(content) click to toggle source

Escape special characters for use inside a CSS content(“…”) string

# File lib/sprockets/server.rb, line 168
def escape_css_content(content)
  content.
    gsub('\', '\\005c ').
    gsub("\n", '\\000a ').
    gsub('"',  '\\0022 ').
    gsub('/',  '\\002f ')
end
etag(asset) click to toggle source

Helper to quote the assets digest for use as an ETag.

# File lib/sprockets/server.rb, line 243
def etag(asset)
  %Q("#{asset.digest}")
end
etag_match?(asset, env) click to toggle source

Compare the requests `HTTP_IF_NONE_MATCH` against the assets digest

# File lib/sprockets/server.rb, line 177
def etag_match?(asset, env)
  env["HTTP_IF_NONE_MATCH"] == etag(asset)
end
forbidden_request?(path) click to toggle source
# File lib/sprockets/server.rb, line 88
def forbidden_request?(path)
  # Prevent access to files elsewhere on the file system
  #
  #     http://example.org/assets/../../../etc/passwd
  #
  path.include?("..") || Pathname.new(path).absolute?
end
forbidden_response() click to toggle source

Returns a 403 Forbidden response tuple

# File lib/sprockets/server.rb, line 97
def forbidden_response
  [ 403, { "Content-Type" => "text/plain", "Content-Length" => "9" }, [ "Forbidden" ] ]
end
headers(env, asset, length) click to toggle source
# File lib/sprockets/server.rb, line 196
def headers(env, asset, length)
  Hash.new.tap do |headers|
    # Set content type and length headers
    headers["Content-Type"]   = asset.content_type
    headers["Content-Length"] = length.to_s

    # Set caching headers
    headers["Cache-Control"]  = "public"
    headers["Last-Modified"]  = asset.mtime.httpdate
    headers["ETag"]           = etag(asset)

    # If the request url contains a fingerprint, set a long
    # expires on the response
    if path_fingerprint(env["PATH_INFO"])
      headers["Cache-Control"] << ", max-age=31536000"

    # Otherwise set `must-revalidate` since the asset could be modified.
    else
      headers["Cache-Control"] << ", must-revalidate"
    end
  end
end
javascript_exception_response(exception) click to toggle source

Returns a JavaScript response that re-throws a Ruby exception in the browser

# File lib/sprockets/server.rb, line 108
def javascript_exception_response(exception)
  err  = "#{exception.class.name}: #{exception.message}"
  body = "throw Error(#{err.inspect})"
  [ 200, { "Content-Type" => "application/javascript", "Content-Length" => Rack::Utils.bytesize(body).to_s }, [ body ] ]
end
not_found_response() click to toggle source

Returns a 404 Not Found response tuple

# File lib/sprockets/server.rb, line 102
def not_found_response
  [ 404, { "Content-Type" => "text/plain", "Content-Length" => "9", "X-Cascade" => "pass" }, [ "Not found" ] ]
end
not_modified_response(asset, env) click to toggle source

Returns a 304 Not Modified response tuple

# File lib/sprockets/server.rb, line 187
def not_modified_response(asset, env)
  [ 304, {}, [] ]
end
ok_response(asset, env) click to toggle source

Returns a 200 OK response tuple

# File lib/sprockets/server.rb, line 192
def ok_response(asset, env)
  [ 200, headers(env, asset, asset.length), asset ]
end
path_fingerprint(path) click to toggle source

Gets digest fingerprint.

"foo-0aa2105d29558f3eb790d411d7d8fb66.js"
# => "0aa2105d29558f3eb790d411d7d8fb66"
# File lib/sprockets/server.rb, line 224
def path_fingerprint(path)
  path[/-([0-9a-f]{7,40})\.[^.]+\z/, 1]
end
unescape(str) click to toggle source
# File lib/sprockets/server.rb, line 231
def unescape(str)
  str = URI::DEFAULT_PARSER.unescape(str)
  str.force_encoding(Encoding.default_internal) if Encoding.default_internal
  str
end