The Amazing Mustermann

Make sure you view the correct docs: latest release, master.

Welcome to Mustermann. Mustermann is your personal string matching expert. As an expert in the field of strings and patterns, Mustermann also has no runtime dependencies and is fully covered with specs and documentation.

Given a string pattern, Mustermann will turn it into an object that behaves like a regular expression and has comparable performance characteristics.

if '/foo/bar' =~ Mustermann.new('/foo/*')
  puts 'it works!'
end

case 'something.png'
when Mustermann.new('foo/*') then puts "prefixed with foo"
when Mustermann.new('*.pdf') then puts "it's a PDF"
when Mustermann.new('*.png') then puts "it's an image"
end

Besides being a Regexp look-alike, Mustermann also adds a params method, that will give you a Sinatra-style hash:

pattern = Mustermann.new('/:prefix/*.*')
pattern.params('/a/b.c') # => { "prefix" => "a", splat => ["b", "c"] }

Similarly, it is also possible to generate a string from a pattern by expanding it with such a hash:

pattern = Mustermann.new('/:file(.:ext)?')
pattern.expand(file: 'pony')             # => "/pony"
pattern.expand(file: 'pony', ext: 'jpg') # => "/pony.jpg"

It's generally a good idea to reuse pattern objects, since as much computation as possible is happening during object creation, so that the actual matching or expanding is quite fast.

Types and Options

You can pass in additional options to take fine grained control over the pattern:

Mustermann.new('/:foo.:bar', capture: :alpha) # :foo and :bar will only match alphabetic characters

In fact, you can even completely change the pattern type:

Mustermann.new('/**/*.png', type: :shell)

The available types are:

Type	Description	Example	Available Options
identity	URI unescaped input string has to match exactly	/image.png	ignore_unknown_options, uri_decode
rails	Rails style patterns	/:slug(.:ext)	capture, except, greedy, ignore_unknown_options, space_matches_plus, uri_decode
shell	Unix style patterns	/*.{png,jpg}	ignore_unknown_options, uri_decode
simple	Sinatra 1.3 style patterns	/:slug.:ext	greedy, ignore_unknown_options, space_matches_plus, uri_decode
sinatra	Sinatra 2.0 style patterns (default)	/:slug(.:ext)?	capture, except, greedy, ignore_unknown_options, space_matches_plus, uri_decode
template	URI templates	/dictionary/{term}	capture, except, greedy, ignore_unknown_options, space_matches_plus, uri_decode

See below for more details.

Sinatra Integration

All patterns implement match, which means they can be dropped into Sinatra and other Rack routers:

require 'sinatra'
require 'mustermann'

get Mustermann.new('/:foo') do
  params[:foo]
end

In fact, since using this with Sinatra is the main use case, it comes with a build-in extension for Sinatra 1.x.

require 'sinatra'
require 'mustermann'

register Mustermann

# this will use Mustermann rather than the built-in pattern matching
get '/:slug(.ext)?' do
  params[:slug]
end

Configuration

You can change what pattern type you want to use for your app via the pattern option:

require 'sinatra/base'
require 'mustermann'

class MyApp < Sinatra::Base
  register Mustermann
  set :pattern, type: :shell

  get '/images/*.png' do
    send_file request.path_info
  end

  get '/index{.htm,.html,}' do
    erb :index
  end
end

You can use the same setting for options:

require 'sinatra'
require 'mustermann'

register Mustermann
set :pattern, capture: { ext: %w[png jpg html txt] }

get '/:slug(.:ext)?' do
  # slug will be 'foo' for '/foo.png'
  # slug will be 'foo.bar' for '/foo.bar'
  # slug will be 'foo.bar' for '/foo.bar.html'
  params[:slug]
end

It is also possible to pass in options to a specific route:

require 'sinatra'
require 'mustermann'

register Mustermann

get '/:slug(.:ext)?', pattern: { greedy: false } do
  # slug will be 'foo' for '/foo.png'
  # slug will be 'foo' for '/foo.bar'
  # slug will be 'foo' for '/foo.bar.html'
  params[:slug]
end

Of course, all of the above can be combined. Moreover, the capture and the except option can be passed to route directly. And yes, this also works with before and after filters.

require 'sinatra/base'
require 'sinatra/respond_with'
require 'mustermann'

class MyApp < Sinatra::Base
  register Mustermann, Sinatra::RespondWith
  set :pattern, capture: { id: /\d+/ } # id will only match digits

  # only capture extensions known to Rack
  before '*:ext', capture: Rack::Mime::MIME_TYPES.keys do
    content_type params[:ext]                 # set Content-Type
    request.path_info = params[:splat].first  # drop the extension
  end

  get '/:id' do
    not_found unless page = Page.find params[:id]
    respond_with(page)
  end
end

Why would I want this?

• It gives you fine grained control over the pattern matching
• Allows you to use different pattern styles in your app
• The default is more robust and powerful than the built-in patterns
• Sinatra 2.0 will use Mustermann internally
• Better exceptions for broken route syntax

Why not include this in Sinatra 1.x?

• It would introduce breaking changes, even though these would be minor
• Like Sinatra 2.0, Mustermann requires Ruby 2.0 or newer

Partial Loading and Thread Safety

Pattern objects are generally assumed to be thread-safe. You can easily match strings against the same pattern object concurrently.

Mustermann will only load the pattern implementation you need. For example, mustermann/rails is loaded the first time you invoke Mustermann.new(..., type: :rails). This part might not be thread-safe, depending on your Ruby implementation.

In the common use cases, that is Sinatra and similar, patterns are compiled on the main thread during the application load phase, so this is a non-issue there.

To avoid this, you can load the pattern types you need manually:

require 'mustermann/sinatra'
Mustermann::Sinatra.new('/:foo')

Options

capture

Supported by: rails, sinatra, template

Sinatra, URI template and Rails patterns support changing the way named captures work via the capture options.

Possible values for a capture:

# String: Matches the given string (or any URI encoded version of it)
Mustermann.new('/index.:ext', capture: 'png')

# Regexp: Matches the Regular expression
Mustermann.new('/:id', capture: /\d+/)

# Symbol: Matches POSIX character class
Mustermann.new('/:id', capture: :digit)

# Array of the above: Matches anything in the array
Mustermann.new('/:id_or_slug', capture: [/\d+/, :word])

# Hash of the above: Looks up the hash entry by capture name and uses value for matching
Mustermann.new('/:id.:ext', capture: { id: /\d+/, ext: ['png', 'jpg'] })

Available POSIX character classes are: :alnum, :alpha, :blank, :cntrl, :digit, :graph, :lower, :print, :punct, :space, :upper, :xdigit, :word and :ascii.

except

Supported by: rails, sinatra, template

Given you supply a second pattern via the except option. Any string that would match the primary pattern but also matches the except pattern will not result in a successful match. Feel free to read that again. Or just take a look at this example:

pattern = Mustermann.new('/auth/*', except: '/auth/login')
pattern === '/auth/dunno' # => true
pattern === '/auth/login' # => false

Now, as said above, except treats the value as a pattern:

pattern = Mustermann.new('/*anything', type: :rails, except: '/*anything.png')
pattern === '/foo.jpg' # => true
pattern === '/foo.png' # => false

greedy

Supported by: rails, simple, sinatra, template. Default value: true

Simple patterns are greedy, meaning that for the pattern :foo:bar?, everything will be captured as foo, bar will always be nil. By setting greedy to false, foo will capture as little as possible (which in this case would only be the first letter), leaving the rest to bar.

Sinatra, URI template and Rails patterns are semi-greedy. This means :foo(.:bar)? (:foo(.:bar) for Rails patterns) will capture everything before the last dot as foo. For these two pattern types, you can switch into non-greedy mode by setting the greedy option to false. In that case foo will only capture the part before the first dot.

Semi-greedy behavior is not specific to dots, it works with all characters or strings. For instance, :a(foo:b) will capture everything before the last foo as a, and :foo(bar)? will not capture a bar at the end.

pattern = Mustermann.new(':a.:b', greedy: true)
pattern.match('a.b.c.d') # => #<MatchData a:"a.b.c" b:"d">

pattern = Mustermann.new(':a.:b', greedy: false)
pattern.match('a.b.c.d') # => #<MatchData a:"a" b:"b.c.d">

space_matches_plus

Supported by: rails, simple, sinatra, template. Default value: true

Sinatra, Simple, URI template and Rails patterns will by default also match a plus sign for a space in the pattern:

Mustermann.new('a b') === 'a+b' # => true

You can disable this behavior via space_matches_plus:

Mustermann.new('a b', space_matches_plus: false) === 'a+b' # => false

Important: This setting has no effect on captures, captures will always keep plus signs as plus sings and spaces as spaces:

pattern = Mustermann.new(':x')
pattern.match('a b')[:x] # => 'a b'
pattern.match('a+b')[:x] # => 'a+b'

uri_decode

Supported by all patterns. Default value: true

Usually, characters in the pattern will also match the URI encoded version of these characters:

Mustermann.new('a b') === 'a b'   # => true
Mustermann.new('a b') === 'a%20b' # => true

You can avoid this by setting uri_decode to false:

Mustermann.new('a b', uri_decode: false) === 'a b'   # => true
Mustermann.new('a b', uri_decode: false) === 'a%20b' # => false

ignore_unknown_options

Supported by all patterns. Default value: false

If you pass an option in that is not supported by the specific pattern type, Mustermann will raise an ArgumentError. By setting ignore_unknown_options to true, it will happily ignore the option.

Pattern Types

identity

Patterns that are no real patterns, just string matching.

Syntax Element	Description
any character	Matches exactly that character or a URI escaped version of it.

rails

Patterns with the syntax used in Rails route definitions.

Syntax Element	Description
:name	Captures anything but a forward slash in a semi-greedy fashion. Capture is named name. Capture behavior can be modified with capture and greedy option.
*name	Captures anything in a non-greedy fashion. Capture is named name.
(expression)	Enclosed expression is optional.
/	Matches forward slash. Does not match URI encoded version of forward slash.
any other character	Matches exactly that character or a URI encoded version of it.

shell

Shell patterns, as used in Bash or with Dir.glob.

Syntax Element	Description
*	Matches anything but a slash.
**	Matches anything.
[set]	Matches one character in set.
{a,b}	Matches a or b.
\x	Matches x or URI encoded version of x. For instance \* matches *.
any other character	Matches exactly that character or a URI encoded version of it.

simple

Patterns as used by Sinatra 1.3. Useful for porting an application that relies on this behavior to a later Sinatra version and to make sure Sinatra 2.0 patterns do not decrease performance.

Syntax Element	Description
:name	Captures anything but a forward slash in a greedy fashion. Capture is named name.
*	Captures anything in a non-greedy fashion. Capture is named splat. It is always an array of captures, as you can use * more than once in a pattern.
x?	Makes x optional. For instance foo? matches foo or fo.
/	Matches forward slash. Does not match URI encoded version of forward slash.
any special character	Matches exactly that character or a URI encoded version of it.
any other character	Matches exactly that character.

sinatra

Sinatra 2.0 style patterns. The default used by Mustermann.

Syntax Element	Description
:name	Captures anything but a forward slash in a semi-greedy fashion. Capture is named name. Capture behavior can be modified with capture and greedy option.
*	Captures anything in a non-greedy fashion. Capture is named splat. It is always an array of captures, as you can use * more than once in a pattern.
(expression)	Enclosed expression is a group. Useful when combined with ? to make it optional, or to separate two elements that would otherwise be parsed as one.
x?	Makes x optional. For instance (foo)? matches foo or an empty string.
/	Matches forward slash. Does not match URI encoded version of forward slash.
\x	Matches x or URI encoded version of x. For instance \* matches *.
any other character	Matches exactly that character or a URI encoded version of it.

template

Parses fully expanded URI templates as specified by RFC 6570.

Note that it differs from URI templates in that it takes the unescaped version of special character instead of the escaped version.

Syntax Element	Description
{o var m, var m, ...}	Captures expansion. Operator o: + # . / ; ? & or none. Modifier m: :num * or none.
/	Matches forward slash. Does not match URI encoded version of forward slash.
any other character	Matches exactly that character or a URI encoded version of it.

The operators + and # will always match non-greedy, whereas all other operators match semi-greedy by default. All modifiers and operators are supported. However, it does not parse lists as single values without the explode modifier (aka star). Parametric operators (;, ? and &) currently only match parameters in given order.

pattern = Mustermann.new("{/segments*}/{page}{.ext,cmpr:2}", type: :template)
pattern.params("/a/b/c.tar.gz") # => {"segments"=>["a","b"], "page"=>"c", "ext"=>"tar", "cmpr"=>"gz"}

Please keep the following in mind:

"Some URI Templates can be used in reverse for the purpose of variable matching: comparing the template to a fully formed URI in order to extract the variable parts from that URI and assign them to the named variables. Variable matching only works well if the template expressions are delimited by the beginning or end of the URI or by characters that cannot be part of the expansion, such as reserved characters surrounding a simple string expression. In general, regular expression languages are better suited for variable matching." — RFC 6570, Sec 1.5: "Limitations"

If you reuse the exact same templates and expose them via an external API meant for expansion, you should set uri_decode to false in order to conform with the specification.

If you are looking for an alternative implementation that also supports expanding, check out addressable.

Requirements

Mustermann has no dependencies besides a Ruby 2.0 compatible Ruby implementation.

It is known to work on MRI 2.0 and MRI trunk. JRuby is not yet supported, but is likely to follow soon (see issue #2 for up to date information on JRuby). Rubinius is not yet able to parse the Mustermann source code.

Release History

Mustermann follows Semantic Versioning 2.0. Anything documented in the README or via YARD and not declared private is part of the public API.

Stable Releases

There have been no stable releases yet. The code base is considered solid but I don't know of anyone using it in production yet. As there has been no stable release yet, the API might still change, though I consider this unlikely.

Development Releases

• Mustermann 0.0.1 (2013-04-27)
  • More Infos: RubyGems.org, RubyDoc.info, GitHub.com
  • Initial Release.
• Mustermann 0.1.0 (2013-05-12)
  • Add Pattern#expand for generating strings from patterns.
  • Add better internal API for working with the AST.
  • Improved documentation.
  • Avoids parsing the path twice when used as Sinatra extension.
  • Better exceptions for unknown pattern types.
  • Better handling of edge cases around extend.
  • More specs to ensure API stability.
  • Largely rework internals of Sinatra, Rails and Template patterns.

Upcoming Releases

• Mustermann 0.2.0 (next release with new features)
• Mustermann 1.0.0 (before Sinatra 2.0)
  • First stable release.