add vary option

Changes

@@ -1,6 +1,7 @@
 Revision history for {{$dist->name}}
 
 {{$NEXT}}
+  - Add vary option (gh#5)
 
 0.01      2024-05-10 11:53:04 -0600
   - initial version

README.md

@@ -33,6 +33,12 @@ request header.
     Compression level.  Should be an integer from 1 to 22.  If not provided, then the default will
     be chosen by [Compress::Stream::Zstd](https://metacpan.org/pod/Compress::Stream::Zstd).
 
+- vary
+
+    If set to true (the default), then the response will vary on `Content-Encoding`.  This is usually
+    what you want, but if you have another middleware or application that is already vary'ing on that
+    header, you may want to set this to false.
+
 # SEE ALSO
 
 - [Plack::Middleware::Deflater](https://metacpan.org/pod/Plack::Middleware::Deflater)

author.yml

@@ -7,6 +7,8 @@ pod_spelling_system:
   # intentionally
   stopwords:
     - Zstandard
+    - ing
+    - vary'ing
 
 pod_coverage:
   skip: 0

lib/Plack/Middleware/Zstandard.pm

@@ -8,7 +8,7 @@ package Plack::Middleware::Zstandard {
 
   use parent qw( Plack::Middleware );
   use Plack::Util ();
-  use Plack::Util::Accessor qw( level _constructor_args );
+  use Plack::Util::Accessor qw( level _constructor_args vary );
   use Ref::Util qw( is_plain_arrayref );
   use Compress::Stream::Zstd::Compressor ();
 
@@ -31,9 +31,11 @@ package Plack::Middleware::Zstandard {
       return undef if Plack::Util::status_with_no_entity_body($res->[0]);
       return undef if $h->exists('Cache-Control') && $h->get('Cache-Control') =~ /\bno-transform\b/;
 
-      my @vary = split /\s*,\s*/, ($h->get('Vary') || '');
-      push @vary, 'Accept-Encoding';
-      $h->set('Vary' => join(",", @vary));
+      if($self->vary // 1) {
+        my @vary = split /\s*,\s*/, ($h->get('Vary') || '');
+        push @vary, 'Accept-Encoding';
+        $h->set('Vary' => join(",", @vary));
+      }
 
       # Do not clobber already existing encoding
       return if $h->exists('Content-Encoding') && $h->get('Content-Encoding') ne 'identity';
@@ -88,6 +90,12 @@ request header.
 Compression level.  Should be an integer from 1 to 22.  If not provided, then the default will
 be chosen by L<Compress::Stream::Zstd>.
 
+=item vary
+
+If set to true (the default), then the response will vary on C<Content-Encoding>.  This is usually
+what you want, but if you have another middleware or application that is already vary'ing on that
+header, you may want to set this to false.
+
 =back
 
 =head1 SEE ALSO

t/plack_middleware_zstandard.t

@@ -260,7 +260,35 @@ subtest 'level' => sub {
       'expected args',
     );
   };
+};
+
+subtest 'vary' => sub {
+
+  subtest 'do not vary' => sub {
+
+    my $app = psgi_app_guard builder {
+      enable 'Zstandard', vary => 0;
+      sub { return [ 200, ['Content-Type' => 'text/plain'], ['Hello World']] };
+    };
 
+    req(
+      GET('/', 'Accept-Encoding' => 'zstd'),
+      res {
+        code 200;
+        content_type 'text/plain';
+        header 'Content-Length' => DNE();
+        header 'Content-Encoding' => 'zstd';
+        header 'Vary', DNE();
+      },
+    );
+
+    is(
+      decompress(),
+      'Hello World',
+      'content',
+    );
+
+  };
 };
 
 sub note_debug {