Fix AS::Cache 7.1 format to properly compress bare strings

The bare string and compression features weren't working properly
together.

I discovered this while trying to fix deprecation warnings.

activesupport/lib/active_support/cache/serializer_with_fallback.rb

@@ -159,12 +159,20 @@ module Marshal71WithFallback
           MARK_UNCOMPRESSED = "\x00".b.freeze
           MARK_COMPRESSED   = "\x01".b.freeze
 
+          def dump(entry, raw = false)
+            if raw
+              super(entry)
+            else
+              MARK_UNCOMPRESSED + super(entry)
+            end
+          end
+
           def _dump(entry)
-            MARK_UNCOMPRESSED + Marshal.dump(entry.pack)
+            Marshal.dump(entry.pack)
           end
 
           def dump_compressed(entry, threshold)
-            dumped = Marshal.dump(entry.pack)
+            dumped = dump(entry, true)
             if compressed = try_compress(dumped, threshold)
               MARK_COMPRESSED + compressed
             else
@@ -175,7 +183,7 @@ def dump_compressed(entry, threshold)
           def _load(marked)
             dumped = marked.byteslice(1..-1)
             dumped = decompress(dumped) if marked.start_with?(MARK_COMPRESSED)
-            Cache::Entry.unpack(Marshal.load(dumped))
+            try_load_bare_string(dumped) || Cache::Entry.unpack(Marshal.load(dumped))
           end
 
           def dumped?(dumped)
@@ -186,7 +194,10 @@ def dumped?(dumped)
         module Marshal70WithFallback
           include Marshal71WithFallback
           extend self
-          alias :dump :_dump # Prevent dumping bare strings.
+
+          def try_dump_bare_string(_entry)
+            nil # Prevent dumping bare strings.
+          end
         end
 
         module MessagePackWithFallback

activesupport/test/abstract_unit.rb

@@ -29,6 +29,8 @@
   ActiveSupport.to_time_preserves_timezone = ENV.fetch("PRESERVE_TIMEZONES", "1") == "1"
 end
 
+ActiveSupport::Cache.format_version = 7.1
+
 # Disable available locale checks to avoid warnings running the test suite.
 I18n.enforce_available_locales = false
 

activesupport/test/cache/behaviors/cache_store_format_version_behavior.rb

@@ -10,7 +10,7 @@ module CacheStoreFormatVersionBehavior
   included do
     test "format version affects default coder" do
       coders = FORMAT_VERSIONS.map do |format_version|
-        ActiveSupport::Cache.with(format_version: format_version) do
+        with_format(format_version) do
           lookup_store.instance_variable_get(:@coder)
         end
       end
@@ -19,7 +19,7 @@ module CacheStoreFormatVersionBehavior
     end
 
     test "invalid format version raises" do
-      ActiveSupport::Cache.with(format_version: 0) do
+      with_format(0) do
         assert_raises do
           lookup_store
         end
@@ -30,26 +30,33 @@ module CacheStoreFormatVersionBehavior
       test "format version #{read_version.inspect} can read #{write_version.inspect} entries" do
         key = SecureRandom.uuid
 
-        ActiveSupport::Cache.with(format_version: write_version) do
+        with_format(write_version) do
           lookup_store.write(key, "value for #{key}")
         end
 
-        ActiveSupport::Cache.with(format_version: read_version) do
+        with_format(read_version) do
           assert_equal "value for #{key}", lookup_store.read(key)
         end
       end
 
       test "format version #{read_version.inspect} can read #{write_version.inspect} entries with compression" do
         key = SecureRandom.uuid
 
-        ActiveSupport::Cache.with(format_version: write_version) do
+        with_format(write_version) do
           lookup_store(compress_threshold: 1).write(key, key * 10)
         end
 
-        ActiveSupport::Cache.with(format_version: read_version) do
+        with_format(read_version) do
           assert_equal key * 10, lookup_store.read(key)
         end
       end
     end
   end
+
+  private
+    def with_format(format_version, &block)
+      ActiveSupport.deprecator.silence do
+        ActiveSupport::Cache.with(format_version: format_version, &block)
+      end
+    end
 end