Force encoding of US-ASCII to UTF-8 in unescape_uri.

Because URI paths may contain non US-ASCII characters we need to force
the encoding of any unescaped URIs to UTF-8 if they are US-ASCII.
This essentially replicates the functionality of the monkey patch to
URI.parser.unescape in active_support/core_ext/uri.rb.

Fixes #16104.

actionpack/CHANGELOG.md

@@ -1,3 +1,12 @@
+*   Because URI paths may contain non US-ASCII characters we need to force
+    the encoding of any unescaped URIs to UTF-8 if they are US-ASCII.
+    This essentially replicates the functionality of the monkey patch to
+    URI.parser.unescape in active_support/core_ext/uri.rb.
+
+    Fixes #16104.
+
+    *Karl Entwistle*
+
 *   Generate shallow paths for all children of shallow resources.
 
     Fixes #15783.

actionpack/lib/action_dispatch/journey/router/utils.rb

@@ -25,9 +25,10 @@ module ActionDispatch
         # http://tools.ietf.org/html/rfc3986
         class UriEncoder # :nodoc:
           ENCODE   = "%%%02X".freeze
-          ENCODING = Encoding::US_ASCII
-          EMPTY    = "".force_encoding(ENCODING).freeze
-          DEC2HEX  = (0..255).to_a.map{ |i| ENCODE % i }.map{ |s| s.force_encoding(ENCODING) }
+          US_ASCII = Encoding::US_ASCII
+          UTF_8    = Encoding::UTF_8
+          EMPTY    = "".force_encoding(US_ASCII).freeze
+          DEC2HEX  = (0..255).to_a.map{ |i| ENCODE % i }.map{ |s| s.force_encoding(US_ASCII) }
 
           ALPHA = "a-zA-Z".freeze
           DIGIT = "0-9".freeze
@@ -53,12 +54,13 @@ module ActionDispatch
           end
 
           def unescape_uri(uri)
-            uri.gsub(ESCAPED) { [$&[1, 2].hex].pack('C') }.force_encoding(uri.encoding)
+            encoding = uri.encoding == US_ASCII ? UTF_8 : uri.encoding
+            uri.gsub(ESCAPED) { [$&[1, 2].hex].pack('C') }.force_encoding(encoding)
           end
 
           protected
             def escape(component, pattern)
-              component.gsub(pattern){ |unsafe| percent_encode(unsafe) }.force_encoding(ENCODING)
+              component.gsub(pattern){ |unsafe| percent_encode(unsafe) }.force_encoding(US_ASCII)
             end
 
             def percent_encode(unsafe)

actionpack/test/journey/router/utils_test.rb

@@ -1,3 +1,4 @@
+# coding: utf-8
 require 'abstract_unit'
 
 module ActionDispatch
@@ -20,6 +21,10 @@ module ActionDispatch
           assert_equal "a/b c+d", Utils.unescape_uri("a%2Fb%20c+d")
         end
 
+        def test_uri_unescape_with_utf8_string
+          assert_equal "Šašinková", Utils.unescape_uri("%C5%A0a%C5%A1inkov%C3%A1".force_encoding(Encoding::US_ASCII))
+        end
+
         def test_normalize_path_not_greedy
           assert_equal "/foo%20bar%20baz", Utils.normalize_path("/foo%20bar%20baz")
         end