Fix issue with passed routes and provides

lib/sinatra/base.rb

@@ -882,6 +882,7 @@ def initialize(app = nil)
       super()
       @app = app
       @template_cache = Tilt::Cache.new
+      @pinned_response = nil # whether a before! filter pinned the content-type
       yield self if block_given?
     end
 
@@ -956,15 +957,21 @@ def forward
     private
 
     # Run filters defined on the class and all superclasses.
+    # Accepts an optional block to call after each filter is applied.
     def filter!(type, base = settings)
       filter! type, base.superclass if base.superclass.respond_to?(:filters)
-      base.filters[type].each { |args| process_route(*args) }
+      base.filters[type].each do |args|
+        result = process_route(*args)
+        yield result if block_given?
+      end
     end
 
     # Run routes defined on the class and all superclasses.
     def route!(base = settings, pass_block = nil)
       if routes = base.routes[@request.request_method]
         routes.each do |pattern, keys, conditions, block|
+          @response['Content-Type'] = nil unless @pinned_response
+
           returned_pass_block = process_route(pattern, keys, conditions) do |*args|
             env['sinatra.route'] = block.instance_variable_get(:@route_name)
             route_eval { block[*args] }
@@ -1080,7 +1087,9 @@ def invoke
     def dispatch!
       invoke do
         static! if settings.static? && (request.get? || request.head?)
-        filter! :before
+        filter! :before do
+          @pinned_response = !@response['Content-Type'].nil?
+        end
         route!
       end
     rescue ::Exception => boom

test/routing_test.rb

@@ -1063,6 +1063,28 @@ class RoutingTest < Minitest::Test
     assert_body 'html'
   end
 
+  it "doesn't allow provides of passed routes to interfere with provides of other routes" do
+    mock_app do
+      get('/:foo', :provides => :txt) do
+        pass if params[:foo] != 'foo'
+
+        'foo'
+      end
+
+      get('/bar', :provides => :html) { 'bar' }
+    end
+
+    get '/foo', {}, { 'HTTP_ACCEPT' => '*/*' }
+    assert ok?
+    assert_equal 'text/plain;charset=utf-8', response.headers['Content-Type']
+    assert_body 'foo'
+
+    get '/bar', {}, { 'HTTP_ACCEPT' => '*/*' }
+    assert ok?
+    assert_equal 'text/html;charset=utf-8', response.headers['Content-Type']
+    assert_body 'bar'
+  end
+
   it "allows multiple mime types for accept header" do
     types = ['image/jpeg', 'image/pjpeg']