before filters can modify request routing variables

Execute the before filters before looking up the
event. Makes it possible for filters to rewrite request
variables such as PATH_INFO and REQUEST_METHOD and have
it effect which route is chosen.

lib/sinatra.rb

@@ -790,7 +790,11 @@ module Sinatra
 
     attr_accessor :request, :response
 
+    attr_accessor :route_params
+
     def initialize(request, response, route_params)
+      @params = nil
+      @data = nil
       @request = request
       @response = response
       @route_params = route_params
@@ -808,10 +812,13 @@ module Sinatra
     end
 
     def params
-      @params ||= begin
-        h = Hash.new {|h,k| h[k.to_s] if Symbol === k}
-        h.merge(@route_params.merge(@request.params))
-      end
+      @params ||=
+        begin
+          hash = Hash.new {|h,k| h[k.to_s] if Symbol === k}
+          hash.merge! @request.params
+          hash.merge! @route_params
+          hash
+        end
     end
 
     def data
@@ -830,6 +837,11 @@ module Sinatra
       request.env['rack.session'] ||= {}
     end
 
+    def reset!
+      @params = nil
+      @data = nil
+    end
+
   private
 
     def method_missing(name, *args, &b)
@@ -1230,13 +1242,15 @@ module Sinatra
     # +env+ argument and return value.
     def dispatch(env)
       request = Rack::Request.new(env)
-      result = lookup(request)
-      context = EventContext.new(request, Rack::Response.new, result.params)
-      context.status(result.status)
+      context = EventContext.new(request, Rack::Response.new([], 200), {})
       begin
         returned =
           catch(:halt) do
             filters[:before].each { |f| context.instance_eval(&f) }
+            result = lookup(context.request)
+            context.route_params = result.params
+            context.response.status = result.status
+            context.reset!
             [:complete, context.instance_eval(&result.block)]
           end
         body = returned.to_result(context)

test/filter_test.rb

@@ -0,0 +1,30 @@
+require File.dirname(__FILE__) + '/helper'
+
+context "before filters" do
+
+  setup do
+    Sinatra.application = nil
+    @app = Sinatra.application
+  end
+
+  specify "should be executed in the order defined" do
+    invoked = 0x0
+    @app.before { invoked = 0x01 }
+    @app.before { invoked |= 0x02 }
+    @app.get('/') { 'Hello World' }
+    get_it '/'
+    should.be.ok
+    body.should.be == 'Hello World'
+    invoked.should.be == 0x03
+  end
+
+  specify "should be capable of modifying the request" do
+    @app.get('/foo') { 'foo' }
+    @app.get('/bar') { 'bar' }
+    @app.before { request.path_info = '/bar' }
+    get_it '/foo'
+    should.be.ok
+    body.should.be == 'bar'
+  end
+
+end