From 8726b29f7c75705671d7c061fc7582d9b35eeae7 Mon Sep 17 00:00:00 2001
From: Jean Boussier <jean.boussier@gmail.com>
Date: Mon, 10 Jan 2022 12:11:51 +0100
Subject: [PATCH] Ignore load path caches generated by a different ruby version

Fix: https://github.com/Shopify/bootsnap/issues/384

Until now it was assume that if the `$LOAD_PATH` was identical,
then the content of the paths would be too.

However from one minor ruby version to another, the layout of the
stdlib can change. So if the newer version is installed in the same
place than the previous one, it might cause the load path cache to
be invalid.

So we store `RUBY_DESCRIPTION` in the cache and make sure it matches
before reusing the cache.
---
 CHANGELOG.md                          |  3 +++
 lib/bootsnap/load_path_cache/store.rb | 18 +++++++++++++++---
 test/load_path_cache/store_test.rb    | 24 ++++++++++++++++++++++++
 3 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6a29ac9c..ba35ccac 100644
--- a/CHANGELOG.md
+++ b/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).
diff --git a/lib/bootsnap/load_path_cache/store.rb b/lib/bootsnap/load_path_cache/store.rb
index 5f5e9fa2..071ca4f4 100644
--- a/lib/bootsnap/load_path_cache/store.rb
+++ b/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
diff --git a/test/load_path_cache/store_test.rb b/test/load_path_cache/store_test.rb
index 74e23544..4fbce665 100644
--- a/test/load_path_cache/store_test.rb
+++ b/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