Do not intern extension type strings

Fix: msgpack#248 (comment)

Extensions might not expect it, and it's unlikely that they'll be kept
as is as binary strings anyway.

ext/msgpack/unpacker.c

@@ -291,21 +291,17 @@ static inline int read_raw_body_begin(msgpack_unpacker_t* uk, int raw_type)
             VALUE symbol = msgpack_buffer_read_top_as_symbol(UNPACKER_BUFFER_(uk), length, raw_type != RAW_TYPE_BINARY);
             ret = object_complete_symbol(uk, symbol);
         } else {
-            /* don't use zerocopy for hash keys but get a frozen string directly
-             * because rb_hash_aset freezes keys and it causes copying */
-            bool will_freeze = uk->freeze || is_reading_map_key(uk);
-            VALUE string = msgpack_buffer_read_top_as_string(UNPACKER_BUFFER_(uk), length, will_freeze, raw_type == RAW_TYPE_STRING);
+            bool will_freeze = uk->freeze;
             if(raw_type == RAW_TYPE_STRING || raw_type == RAW_TYPE_BINARY) {
+               /* don't use zerocopy for hash keys but get a frozen string directly
+                * because rb_hash_aset freezes keys and it causes copying */
+                will_freeze = will_freeze || is_reading_map_key(uk);
+                VALUE string = msgpack_buffer_read_top_as_string(UNPACKER_BUFFER_(uk), length, will_freeze, raw_type == RAW_TYPE_STRING);
                 ret = object_complete(uk, string);
             } else {
+                VALUE string = msgpack_buffer_read_top_as_string(UNPACKER_BUFFER_(uk), length, false, false);
                 ret = object_complete_ext(uk, raw_type, string);
             }
-
-# if !HASH_ASET_DEDUPE
-            if(will_freeze) {
-                rb_obj_freeze(string);
-            }
-# endif
         }
         uk->reading_raw_remaining = 0;
         return ret;

spec/factory_spec.rb

@@ -286,8 +286,8 @@ def to_msgpack_ext
   end
 
   describe 'the special treatment of symbols with ext type' do
-    def roundtrip(object)
-      subject.load(subject.dump(object))
+    def roundtrip(object, options = nil)
+      subject.load(subject.dump(object), options)
     end
 
     context 'using the optimized symbol unpacker' do
@@ -333,6 +333,14 @@ def roundtrip(object)
           expect(roundtrip(:symbol)).to be :symbol
         end
 
+        it 'works with hash keys' do
+          expect(roundtrip(symbol: 1)).to be == { symbol: 1 }
+        end
+
+        it 'works with frozen: true option' do
+          expect(roundtrip(:symbol, freeze: true)).to be :symbol
+        end
+
         it 'preserves encoding for ASCII symbols' do
           expect(:symbol.encoding).to be Encoding::US_ASCII
           expect(roundtrip(:symbol)).to be :symbol