Make default_headers plugin correctly handle mixed/upper case content…

…-type header on Rack 3 (Fixes #373)

Previously, the DEFAULT_HEADERS constant was a plain hash even on
Rack 3, so it didn't handle the folding to lower case.  When using
the default_headers plugin, the given headers were merged into
DEFAULT_HEADERS, so a change in case resulted in duplicate keys in
the resulting hash.  Because default headers do not overwrite
existing headers, the first default header (the lowercase content-type
Roda uses by default) would be kept, instead of the default header
set by the plugin (the mixed case Content-Type).

With this change, the DEFAULT_HEADERS constant is a Rack::Headers
instance, so the mixed/upper case Content-Type will be converted
to lowercase and overwrite the lowercase default, before it is
set in app.opts[:default_headers].

CHANGELOG

@@ -1,5 +1,7 @@
 === master
 
+* Make default_headers plugin correctly handle mixed/upper case content-type header on Rack 3 (jeremyevans) (#373)
+
 * Make json_parser plugin handle case where Rack::Request#POST is called previously for env on Rack 3 (jeremyevans) (#372)
 
 * Fix strict_unused_block warnings when running specs on Ruby 3.4 (jeremyevans)

lib/roda/response.rb

@@ -46,8 +46,6 @@ def inspect
 
       # Instance methods for RodaResponse
       module ResponseMethods
-        DEFAULT_HEADERS = {RodaResponseHeaders::CONTENT_TYPE => "text/html".freeze}.freeze
-
         # The body for the current response.
         attr_reader :body
 
@@ -179,11 +177,15 @@ def write(str)
         private
 
         if defined?(Rack::Headers) && Rack::Headers.is_a?(Class)
+          DEFAULT_HEADERS = Rack::Headers[{RodaResponseHeaders::CONTENT_TYPE => "text/html".freeze}].freeze
+
           # Use Rack::Headers for headers by default on Rack 3
           def _initialize_headers
             Rack::Headers.new
           end
         else
+          DEFAULT_HEADERS = {RodaResponseHeaders::CONTENT_TYPE => "text/html".freeze}.freeze
+
           # Use plain hash for headers by default on Rack 1-2
           def _initialize_headers
             {}

spec/plugin/default_headers_spec.rb

@@ -29,6 +29,18 @@
     req[1].must_equal h
   end
 
+  it "should handle case insensitive headers" do
+    app(:bare) do
+      plugin :default_headers, 'Content-Type' => 'application/json'
+
+      route do |r|
+        ''
+      end
+    end
+
+    header(RodaResponseHeaders::CONTENT_TYPE).must_equal "application/json"
+  end
+
   it "should allow modifying the default headers by reloading the plugin" do
     app(:bare) do
       plugin :default_headers, RodaResponseHeaders::CONTENT_TYPE => 'text/json'