conditional_get.rb in rack-2.2.0

- old
+ new

@@ -1,9 +1,7 @@
 # frozen_string_literal: true
 
-require 'rack/utils'
-
 module Rack
 
   # Middleware that enables conditional GET using If-None-Match and
   # If-Modified-Since. The application should set either or both of the
   # Last-Modified or Etag response headers according to RFC 2616. When
@@ -19,15 +17,17 @@
   class ConditionalGet
     def initialize(app)
       @app = app
     end
 
+    # Return empty 304 response if the response has not been
+    # modified since the last request.
     def call(env)
       case env[REQUEST_METHOD]
       when "GET", "HEAD"
         status, headers, body = @app.call(env)
-        headers = Utils::HeaderHash.new(headers)
+        headers = Utils::HeaderHash[headers]
         if status == 200 && fresh?(env, headers)
           status = 304
           headers.delete(CONTENT_TYPE)
           headers.delete(CONTENT_LENGTH)
           original_body = body
@@ -41,41 +41,43 @@
       end
     end
 
   private
 
+    # Return whether the response has not been modified since the
+    # last request.
     def fresh?(env, headers)
-      modified_since = env['HTTP_IF_MODIFIED_SINCE']
-      none_match     = env['HTTP_IF_NONE_MATCH']
-
-      return false unless modified_since || none_match
-
-      success = true
-      success &&= modified_since?(to_rfc2822(modified_since), headers) if modified_since
-      success &&= etag_matches?(none_match, headers) if none_match
-      success
+      # If-None-Match has priority over If-Modified-Since per RFC 7232
+      if none_match = env['HTTP_IF_NONE_MATCH']
+        etag_matches?(none_match, headers)
+      elsif (modified_since = env['HTTP_IF_MODIFIED_SINCE']) && (modified_since = to_rfc2822(modified_since))
+        modified_since?(modified_since, headers)
+      end
     end
 
+    # Whether the ETag response header matches the If-None-Match request header.
+    # If so, the request has not been modified.
     def etag_matches?(none_match, headers)
-      etag = headers['ETag'] and etag == none_match
+      headers['ETag'] == none_match
     end
 
+    # Whether the Last-Modified response header matches the If-Modified-Since
+    # request header.  If so, the request has not been modified.
     def modified_since?(modified_since, headers)
       last_modified = to_rfc2822(headers['Last-Modified']) and
-        modified_since and
         modified_since >= last_modified
     end
 
+    # Return a Time object for the given string (which should be in RFC2822
+    # format), or nil if the string cannot be parsed.
     def to_rfc2822(since)
       # shortest possible valid date is the obsolete: 1 Nov 97 09:55 A
       # anything shorter is invalid, this avoids exceptions for common cases
       # most common being the empty string
       if since && since.length >= 16
         # NOTE: there is no trivial way to write this in a non exception way
         #   _rfc2822 returns a hash but is not that usable
         Time.rfc2822(since) rescue nil
-      else
-        nil
       end
     end
   end
 end