PerlDancer · veryrusty · Jun 26, 2018 · Jun 26, 2018
diff --git a/lib/Dancer2/Config.pod b/lib/Dancer2/Config.pod
@@ -172,6 +172,19 @@ hard-configured in the proxy if possible. For Apache this would be:
     RequestHeader set X_FORWARDED_PROTO "https"
     RequestHeader set X_FORWARDED_HOST "www.example.com"
 
+=head3 no_default_middleware (boolean)
+
+If set to true, your Dancer2 application will B<NOT> be wrapped with the default
+PSGI middleware. The default middleware wrappers are:
+
+=over 4
+
+=item * L<Plack::Middleware::FixMissingBodyInRedirect>
+
+=item * L<Plack::Middleware::Head>
+
+=back
+
 =head2 Content type / character set
 
 =head3 content_type (string)

diff --git a/lib/Dancer2/Core/App.pm b/lib/Dancer2/Core/App.pm
@@ -1397,11 +1397,7 @@ sub to_app {
         return $response;
     };
 
-    # Wrap with common middleware
-    # FixMissingBodyInRedirect
-    $psgi = Plack::Middleware::FixMissingBodyInRedirect->wrap( $psgi );
-
-    # Only add static content handler if requires
+    # Only add static content handler if required
     if ( $self->config->{'static_handler'} ) {
         # Use App::File to "serve" the static content
         my $static_app = Plack::App::File->new(
@@ -1417,8 +1413,14 @@ sub to_app {
         );
     }
 
-    # Apply Head. After static so a HEAD request on static content DWIM.
-    $psgi = Plack::Middleware::Head->wrap( $psgi );
+    # Wrap with common middleware
+    if ( ! $self->config->{'no_default_middleware'} ) {
+        # FixMissingBodyInRedirect
+        $psgi = Plack::Middleware::FixMissingBodyInRedirect->wrap( $psgi );
+        # Apply Head. After static so a HEAD request on static content DWIM.
+        $psgi = Plack::Middleware::Head->wrap( $psgi );
+    }
+
     return $psgi;
 }
 

diff --git a/lib/Dancer2/Manual.pod b/lib/Dancer2/Manual.pod
@@ -1932,15 +1932,14 @@ If you want to use Plack middlewares, you need to enable them using
 L<Plack::Builder> as such:
 
     # in app.psgi or any other handler
-    use Dancer2;
     use MyApp;
     use Plack::Builder;
 
     builder {
         enable 'Deflater';
         enable 'Session', store => 'File';
         enable 'Debug', panels => [ qw<DBITrace Memory Timer> ];
-        dance;
+        MyApp->to_app;
     };
 
 The nice thing about this setup is that it will work seamlessly through
@@ -1960,17 +1959,41 @@ If you want to set up a middleware for a specific path, you can do that using
 L<Plack::Builder> which uses L<Plack::App::URLMap>:
 
     # in your app.psgi or any other handler
-    use Dancer2;
     use MyApp;
     use Plack::Builder;
 
     my $special_handler = sub { ... };
 
     builder {
-        mount '/'        => dance;
         mount '/special' => $special_handler;
+        mount '/'        => MyApp->to_app;
     };
 
+=head3 Removing default middlewares
+
+By default, a Dancer2 app is automatically wrapped with the following middleware
+
+=over 4
+
+=item * L<Plack::Middleware::FixMissingBodyInRedirect>
+
+=item * L<Plack::Middleware::Head>
+
+=back
+
+You can configure the setting C<no_default_middleware> to a true value to stop your
+Dancer2 app being wrapped with these default middleware layers.
+
+    # in you Dancer2 app or config.yml
+    package MyApp;
+    use Dancer2
+
+    set no_default_middleware => true;
+
+This is necessary if you need to add eTag or ContentMD5 headers to
+C<HEAD> requests, and you are encouraged to manually add those default
+middleware back into your PSGI stack.
+
 =head3 Running on Perl web servers with plackup
 
 A number of Perl web servers supporting PSGI are available on CPAN:
@@ -2019,7 +2042,7 @@ F<app.psgi>) edit it to use L<Plack::Builder>, as described above:
 
     builder {
         enable 'Deflater';
-        dance;
+        MyApp->to_app;
     };
 
 To test if content compression works, trace the HTTP request and response

diff --git a/t/no_default_middleware.t b/t/no_default_middleware.t
@@ -0,0 +1,59 @@
+use strict;
+use warnings;
+use Test::More;
+use Plack::Test;
+use Plack::Builder;
+use HTTP::Request::Common;
+
+use Plack::Middleware::Head;
+use Plack::Middleware::FixMissingBodyInRedirect;
+
+# No default middleware wrappers
+
+{
+    package MyTestApp;
+    use Dancer2;
+    set no_default_middleware => 1;
+
+    get '/' => sub { return 'some content' };
+
+    get '/redirect' => sub { redirect '/' };
+}
+
+
+subtest 'Head' => sub {
+    my $plain = Plack::Test->create( MyTestApp->to_app );
+    my $res = $plain->request( HEAD '/' );
+    ok( length( $res->content ) > 0, 'HEAD request on unwrapped app has content' );
+
+    my $test = Plack::Test->create(
+        builder {
+            enable 'Head';
+            MyTestApp->to_app;
+        }
+    );
+    my $response = $test->request( HEAD '/' );
+    is( length( $response->content ), 0, 'HEAD request on wrapped app has no content' );
+
+    is( $res->header('Content-Length'),
+        $response->header('Content-Length'),
+        'HEAD requests have consistent content length header'
+    );
+};
+
+subtest 'FixMissingBodyInRedirect' => sub {
+    my $plain = Plack::Test->create( MyTestApp->to_app );
+    my $res = $plain->request( GET '/redirect' );
+    is( length( $res->content ), 0, 'GET request that redirects on unwrapped app has no content' );
+
+    my $test = Plack::Test->create(
+        builder {
+            enable 'FixMissingBodyInRedirect';
+            MyTestApp->to_app;
+        }
+    );
+    my $response = $test->request( GET '/redirect' );
+    ok( length( $response->content ) > 0, 'GET request that redirects on wrapped app has content' );
+};
+
+done_testing;