Make route params available during error handler (Fixes #860)

lib/sinatra/base.rb

@@ -1006,6 +1006,9 @@ def process_route(pattern, keys, conditions, block = nil, values = [])
         conditions.each { |c| throw :pass if c.bind(self).call == false }
         block ? block[self, values] : yield(self, values)
       end
+    rescue
+      @env['sinatra.error.params'] = @params
+      raise
     ensure
       @params = original if original
     end
@@ -1088,6 +1091,9 @@ def dispatch!
 
     # Error handling during requests.
     def handle_exception!(boom)
+      if error_params = @env['sinatra.error.params']
+        @params = @params.merge(error_params)
+      end
       @env['sinatra.error'] = boom
 
       if boom.respond_to? :http_status

test/routing_test.rb

@@ -628,6 +628,23 @@ class RoutingTest < Test::Unit::TestCase
     assert_equal 'Hello World', body
   end
 
+  it "makes original request params available in error handler" do
+    mock_app {
+      disable :raise_errors
+
+      get '/:foo' do
+        raise ArgumentError, "foo"
+      end
+
+      error do
+        "Hello #{params['foo']}2"
+      end
+    }
+
+    get '/bar'
+    assert_equal 'Hello bar2', body
+  end
+
   it "transitions to 404 when passed and no subsequent route matches" do
     mock_app {
       get '/:foo' do