Ignore load path caches generated by a different ruby version

CHANGELOG.md

@@ -1,5 +1,8 @@
 # Unreleased
 
+* Automatically invalidate the load path cache whenever the Ruby version change. (#387)
+  This is to avoid issues in case the same installation path is re-used for subsequent ruby patch releases.
+
 # 1.9.3
 
 * Only disable the compile cache for source files impacted by [Ruby 3.0.3 [Bug 18250]](https://bugs.ruby-lang.org/issues/18250).

lib/bootsnap/load_path_cache/store.rb

@@ -7,6 +7,9 @@
 module Bootsnap
   module LoadPathCache
     class Store
+      VERSION_KEY = '__bootsnap_ruby_version__'
+      CURRENT_VERSION = "#{RUBY_REVISION}-#{RUBY_PLATFORM}".freeze
+
       NestedTransactionError = Class.new(StandardError)
       SetOutsideTransactionNotAllowed = Class.new(StandardError)
 
@@ -62,15 +65,20 @@ def commit_transaction
 
       def load_data
         @data = begin
-          File.open(@store_path, encoding: Encoding::BINARY) do |io|
+          data = File.open(@store_path, encoding: Encoding::BINARY) do |io|
             MessagePack.load(io)
           end
+          if data.is_a?(Hash) && data[VERSION_KEY] == CURRENT_VERSION
+            data
+          else
+            default_data
+          end
         # handle malformed data due to upgrade incompatibility
         rescue Errno::ENOENT, MessagePack::MalformedFormatError, MessagePack::UnknownExtTypeError, EOFError
-          {}
+          default_data
         rescue ArgumentError => error
           if error.message =~ /negative array size/
-            {}
+            default_data
           else
             raise
           end
@@ -93,6 +101,10 @@ def dump_data
         retry
       rescue SystemCallError
       end
+
+      def default_data
+        { VERSION_KEY => CURRENT_VERSION }
+      end
     end
   end
 end

test/load_path_cache/store_test.rb

@@ -80,6 +80,30 @@ def test_ignore_read_only_filesystem
         store.transaction { store.set('a', 1) }
         refute(File.exist?(@path))
       end
+
+      def test_bust_cache_on_ruby_change
+        store.transaction { store.set('a', 'b') }
+
+        assert_equal 'b', Store.new(@path).get('a')
+
+        stub_const(Store, :CURRENT_VERSION, "foobar") do
+          assert_nil Store.new(@path).get('a')
+        end
+      end
+
+      private
+
+      def stub_const(owner, const_name, stub_value)
+        original_value = owner.const_get(const_name)
+        owner.send(:remove_const, const_name)
+        owner.const_set(const_name, stub_value)
+        begin
+          yield
+        ensure
+          owner.send(:remove_const, const_name)
+          owner.const_set(const_name, original_value)
+        end
+      end
     end
   end
 end