deflater: remove "deflate" encoding support no-deflate

This will improve cache hit rates and reduce caching overhead at
small expense of increased header overhead for some user agents.
For reference, Varnish cache supports only gzip as well:

	https://www.varnish-cache.org/docs/4.1/phk/gzip.html

In the past, "deflate" encoding was more likely to trigger
user-agent bugs, as noted in the comments removed with this
change as well as the Varnish documentation referenced above.

2 files changed, 25 insertions, 50 deletions

diff --git a/lib/rack/deflater.rb b/lib/rack/deflater.rb
index 62a11243..79e39f51 100644
--- a/lib/rack/deflater.rb
+++ b/lib/rack/deflater.rb
@@ -8,7 +8,6 @@ module Rack
   # Currently supported compression algorithms:
   #
   #   * gzip
-  #   * deflate
   #   * identity (no transformation)
   #
   # The middleware automatically detects when compression is supported
@@ -41,7 +40,7 @@ module Rack
 
       request = Request.new(env)
 
-      encoding = Utils.select_best_encoding(%w(gzip deflate identity),
+      encoding = Utils.select_best_encoding(%w(gzip identity),
                                             request.accept_encoding)
 
       # Set the Vary HTTP header.
@@ -57,10 +56,6 @@ module Rack
         mtime = headers.key?("Last-Modified") ?
           Time.httpdate(headers["Last-Modified"]) : Time.now
         [status, headers, GzipStream.new(body, mtime)]
-      when "deflate"
-        headers['Content-Encoding'] = "deflate"
-        headers.delete(CONTENT_LENGTH)
-        [status, headers, DeflateStream.new(body)]
       when "identity"
         [status, headers, body]
       when nil
@@ -101,36 +96,6 @@ module Rack
       end
     end
 
-    class DeflateStream
-      DEFLATE_ARGS = [
-        Zlib::DEFAULT_COMPRESSION,
-        # drop the zlib header which causes both Safari and IE to choke
-        -Zlib::MAX_WBITS,
-        Zlib::DEF_MEM_LEVEL,
-        Zlib::DEFAULT_STRATEGY
-      ]
-
-      def initialize(body)
-        @body = body
-        @closed = false
-      end
-
-      def each
-        deflator = ::Zlib::Deflate.new(*DEFLATE_ARGS)
-        @body.each { |part| yield deflator.deflate(part, Zlib::SYNC_FLUSH) }
-        yield fin = deflator.finish
-      ensure
-        deflator.finish unless fin
-        deflator.close
-      end
-
-      def close
-        return if @closed
-        @closed = true
-        @body.close if @body.respond_to?(:close)
-      end
-    end
-
     private
 
     def should_deflate?(env, status, headers, body)
diff --git a/test/spec_deflater.rb b/test/spec_deflater.rb
index ba7ec5d3..0f27c859 100644
--- a/test/spec_deflater.rb
+++ b/test/spec_deflater.rb
@@ -81,13 +81,22 @@ describe Rack::Deflater do
     yield(status, headers, body) if block_given?
   end
 
+  # automatic gzip detection (streamable)
+  def auto_inflater
+    Zlib::Inflate.new(32 + Zlib::MAX_WBITS)
+  end
+
+  def deflate_or_gzip
+    {'deflate, gzip' => 'gzip'}
+  end
+
   it 'be able to deflate bodies that respond to each' do
     app_body = Object.new
     class << app_body; def each; yield('foo'); yield('bar'); end; end
 
-    verify(200, 'foobar', 'deflate', { 'app_body' => app_body }) do |status, headers, body|
+    verify(200, 'foobar', deflate_or_gzip, { 'app_body' => app_body }) do |status, headers, body|
       headers.must_equal({
-        'Content-Encoding' => 'deflate',
+        'Content-Encoding' => 'gzip',
         'Vary' => 'Accept-Encoding',
         'Content-Type' => 'text/plain'
       })
@@ -98,15 +107,15 @@ describe Rack::Deflater do
     app_body = Object.new
     class << app_body; def each; yield('foo'); yield('bar'); end; end
 
-    verify(200, app_body, 'deflate', { 'skip_body_verify' => true }) do |status, headers, body|
+    verify(200, app_body, deflate_or_gzip, { 'skip_body_verify' => true }) do |status, headers, body|
       headers.must_equal({
-        'Content-Encoding' => 'deflate',
+        'Content-Encoding' => 'gzip',
         'Vary' => 'Accept-Encoding',
         'Content-Type' => 'text/plain'
       })
 
       buf = []
-      inflater = Zlib::Inflate.new(-Zlib::MAX_WBITS)
+      inflater = auto_inflater
       body.each { |part| buf << inflater.inflate(part) }
       buf << inflater.finish
 
@@ -118,32 +127,33 @@ describe Rack::Deflater do
     app_body = Object.new
     class << app_body; def each; yield('foo'); yield('bar'); end; end
     opts = { 'skip_body_verify' => true }
-    verify(200, app_body, 'deflate', opts) do |status, headers, body|
+    verify(200, app_body, 'gzip', opts) do |status, headers, body|
       headers.must_equal({
-        'Content-Encoding' => 'deflate',
+        'Content-Encoding' => 'gzip',
         'Vary' => 'Accept-Encoding',
         'Content-Type' => 'text/plain'
       })
 
       buf = []
-      inflater = Zlib::Inflate.new(-Zlib::MAX_WBITS)
+      inflater = auto_inflater
       FakeDisconnect = Class.new(RuntimeError)
       assert_raises(FakeDisconnect, "not Zlib::DataError not raised") do
         body.each do |part|
-          buf << inflater.inflate(part)
+          tmp = inflater.inflate(part)
+          buf << tmp if tmp.bytesize > 0
           raise FakeDisconnect
         end
       end
-      assert_raises(Zlib::BufError) { inflater.finish }
+      inflater.finish
       buf.must_equal(%w(foo))
     end
   end
 
   # TODO: This is really just a special case of the above...
   it 'be able to deflate String bodies' do
-    verify(200, 'Hello world!', 'deflate') do |status, headers, body|
+    verify(200, 'Hello world!', deflate_or_gzip) do |status, headers, body|
       headers.must_equal({
-        'Content-Encoding' => 'deflate',
+        'Content-Encoding' => 'gzip',
         'Vary' => 'Accept-Encoding',
         'Content-Type' => 'text/plain'
       })
@@ -280,7 +290,7 @@ describe Rack::Deflater do
         'Content-Encoding' => 'identity'
       }
     }
-    verify(200, 'Hello World!', 'deflate', options)
+    verify(200, 'Hello World!', deflate_or_gzip, options)
   end
 
   it "deflate if content-type matches :include" do
@@ -334,7 +344,7 @@ describe Rack::Deflater do
         :if => lambda { |env, status, headers, body| true }
       }
     }
-    verify(200, 'Hello World!', 'deflate', options)
+    verify(200, 'Hello World!', deflate_or_gzip, options)
   end
 
   it "not deflate if :if lambda evaluates to false" do