Do not load redis gem when incompatible

Matrixfile

@@ -229,6 +229,9 @@
     'rails6-semantic-logger'  => '✅ 2.5 / ✅ 2.6 / ✅ 2.7 / ❌ 3.0 / ❌ 3.1 / ❌ 3.2 / ❌ 3.3 / ❌ 3.4 / ✅ jruby',
     'rails61-semantic-logger' => '✅ 2.5 / ✅ 2.6 / ✅ 2.7 / ✅ 3.0 / ✅ 3.1 / ✅ 3.2 / ✅ 3.3 / ✅ 3.4 / ✅ jruby'
   },
+  'rails_old_redis' => {
+    'rails-old-redis' => '✅ 2.5 / ✅ 2.6 / ✅ 2.7 / ✅ 3.0 / ✅ 3.1 / ✅ 3.2 / ✅ 3.3 / ✅ 3.4 / ✅ jruby',
+  },
   'action_cable' => {
     # FIXME: Enable the test for JRuby after fixing `log writing failed. closed stream` in CircleCI.
     'rails5-mysql2'  => '✅ 2.5 / ✅ 2.6 / ❌ 2.7 / ❌ 3.0 / ❌ 3.1 / ❌ 3.2 / ❌ 3.3 / ❌ 3.4 / ❌ jruby',

Rakefile

@@ -153,6 +153,15 @@ namespace :spec do
     t.rspec_opts = args.to_a.join(' ')
   end
 
+  # Tests if Datadog::Tracing::Contrib::ActiveSupport::Cache::Redis::Patcher does not eager load
+  # ActiveSupport::Cache::RedisCacheStore when the version of Redis present is too old to be compatible.
+  # @see Datadog::Tracing::Contrib::ActiveSupport::Cache::Redis::Patcher#patch_redis_cache_store?
+  desc '' # "Explicitly hiding from `rake -T`"
+  RSpec::Core::RakeTask.new(:rails_old_redis) do |t, args|
+    t.pattern = 'spec/datadog/tracing/contrib/rails/cache_spec.rb'
+    t.rspec_opts = args.to_a.join(' ')
+  end
+
   desc '' # "Explicitly hiding from `rake -T`"
   RSpec::Core::RakeTask.new(:hanami) do |t, args|
     t.pattern = 'spec/datadog/tracing/contrib/hanami/**/*_spec.rb'

appraisal/jruby-9.2.rb

@@ -151,6 +151,16 @@
   gem 'i18n', '1.8.7', platform: :jruby # Removal pending: https://github.com/ruby-i18n/i18n/issues/555#issuecomment-772112169
 end
 
+appraise 'rails-old-redis' do
+  # All dependencies except Redis < 4 are not important, they are just required to run Rails tests.
+  gem 'redis', '< 4'
+  gem 'rails', '~> 6.1.0'
+  gem 'activerecord-jdbcpostgresql-adapter', platform: :jruby
+  gem 'sprockets', '< 4'
+  gem 'lograge', '~> 0.11'
+  gem 'net-smtp'
+end
+
 appraise 'resque2-redis3' do
   gem 'redis', '< 4.0'
   gem 'resque', '>= 2.0'

appraisal/jruby-9.3.rb

@@ -131,6 +131,16 @@
   gem 'rails_semantic_logger', '~> 4.0'
 end
 
+appraise 'rails-old-redis' do
+  # All dependencies except Redis < 4 are not important, they are just required to run Rails tests.
+  gem 'redis', '< 4'
+  gem 'rails', '~> 6.1.0'
+  gem 'activerecord-jdbcpostgresql-adapter', platform: :jruby
+  gem 'sprockets', '< 4'
+  gem 'lograge', '~> 0.11'
+  gem 'net-smtp'
+end
+
 appraise 'resque2-redis3' do
   gem 'redis', '~> 3.0'
   gem 'resque', '>= 2.0'

appraisal/jruby-9.4.rb

@@ -41,6 +41,16 @@
   gem 'net-smtp'
 end
 
+appraise 'rails-old-redis' do
+  # All dependencies except Redis < 4 are not important, they are just required to run Rails tests.
+  gem 'redis', '< 4'
+  gem 'rails', '~> 6.1.0'
+  gem 'activerecord-jdbcpostgresql-adapter', platform: :jruby
+  gem 'sprockets', '< 4'
+  gem 'lograge', '~> 0.11'
+  gem 'net-smtp'
+end
+
 appraise 'resque2-redis3' do
   gem 'redis', '< 4.0'
   gem 'resque', '>= 2.0'

appraisal/ruby-2.5.rb

@@ -184,6 +184,15 @@
   gem 'rails_semantic_logger', '~> 4.0'
 end
 
+appraise 'rails-old-redis' do
+  # All dependencies except Redis < 4 are not important, they are just required to run Rails tests.
+  gem 'redis', '< 4'
+  gem 'rails', '~> 6.1.0'
+  gem 'pg', '>= 1.1', platform: :ruby
+  gem 'sprockets', '< 4'
+  gem 'lograge', '~> 0.11'
+end
+
 appraise 'resque2-redis3' do
   gem 'redis', '< 4.0'
   gem 'resque', '>= 2.0'

appraisal/ruby-2.6.rb

@@ -137,6 +137,15 @@
   gem 'rails_semantic_logger', '~> 4.0'
 end
 
+appraise 'rails-old-redis' do
+  # All dependencies except Redis < 4 are not important, they are just required to run Rails tests.
+  gem 'redis', '< 4'
+  gem 'rails', '~> 6.1.0'
+  gem 'pg', '>= 1.1', platform: :ruby
+  gem 'sprockets', '< 4'
+  gem 'lograge', '~> 0.11'
+end
+
 appraise 'resque2-redis3' do
   gem 'redis', '~> 3.0'
   gem 'resque', '>= 2.0'

appraisal/ruby-2.7.rb

@@ -137,6 +137,15 @@
   gem 'rails_semantic_logger', '~> 4.0'
 end
 
+appraise 'rails-old-redis' do
+  # All dependencies except Redis < 4 are not important, they are just required to run Rails tests.
+  gem 'redis', '< 4'
+  gem 'rails', '~> 6.1.0'
+  gem 'pg', '>= 1.1', platform: :ruby
+  gem 'sprockets', '< 4'
+  gem 'lograge', '~> 0.11'
+end
+
 appraise 'resque2-redis3' do
   gem 'redis', '< 4.0'
   gem 'resque', '>= 2.0'

appraisal/ruby-3.0.rb

@@ -58,6 +58,15 @@
   gem 'rails', '~> 7.1.0'
 end
 
+appraise 'rails-old-redis' do
+  # All dependencies except Redis < 4 are not important, they are just required to run Rails tests.
+  gem 'redis', '< 4'
+  gem 'rails', '~> 6.1.0'
+  gem 'pg', '>= 1.1', platform: :ruby
+  gem 'sprockets', '< 4'
+  gem 'lograge', '~> 0.11'
+end
+
 appraise 'resque2-redis3' do
   gem 'redis', '< 4.0'
   gem 'resque', '>= 2.0'

appraisal/ruby-3.1.rb

@@ -58,6 +58,15 @@
   gem 'rails', '~> 7.1.0'
 end
 
+appraise 'rails-old-redis' do
+  # All dependencies except Redis < 4 are not important, they are just required to run Rails tests.
+  gem 'redis', '< 4'
+  gem 'rails', '~> 6.1.0'
+  gem 'pg', '>= 1.1', platform: :ruby
+  gem 'sprockets', '< 4'
+  gem 'lograge', '~> 0.11'
+end
+
 appraise 'resque2-redis3' do
   gem 'redis', '< 4.0'
   gem 'resque', '>= 2.0'

appraisal/ruby-3.2.rb

@@ -58,6 +58,15 @@
   gem 'rails', '~> 7.1.0'
 end
 
+appraise 'rails-old-redis' do
+  # All dependencies except Redis < 4 are not important, they are just required to run Rails tests.
+  gem 'redis', '< 4'
+  gem 'rails', '~> 6.1.0'
+  gem 'pg', '>= 1.1', platform: :ruby
+  gem 'sprockets', '< 4'
+  gem 'lograge', '~> 0.11'
+end
+
 appraise 'resque2-redis3' do
   gem 'redis', '< 4.0'
   gem 'resque', '>= 2.0'

appraisal/ruby-3.3.rb

@@ -58,6 +58,15 @@
   gem 'rails', '~> 7.1.0'
 end
 
+appraise 'rails-old-redis' do
+  # All dependencies except Redis < 4 are not important, they are just required to run Rails tests.
+  gem 'redis', '< 4'
+  gem 'rails', '~> 6.1.0'
+  gem 'pg', '>= 1.1', platform: :ruby
+  gem 'sprockets', '< 4'
+  gem 'lograge', '~> 0.11'
+end
+
 appraise 'resque2-redis3' do
   gem 'redis', '< 4.0'
   gem 'resque', '>= 2.0'

appraisal/ruby-3.4.rb

@@ -58,6 +58,15 @@
   gem 'rails', '~> 7.1.0'
 end
 
+appraise 'rails-old-redis' do
+  # All dependencies except Redis < 4 are not important, they are just required to run Rails tests.
+  gem 'redis', '< 4'
+  gem 'rails', '~> 6.1.0'
+  gem 'pg', '>= 1.1', platform: :ruby
+  gem 'sprockets', '< 4'
+  gem 'lograge', '~> 0.11'
+end
+
 appraise 'resque2-redis3' do
   gem 'redis', '< 4.0'
   gem 'resque', '>= 2.0'

lib/datadog/tracing/contrib/active_support/cache/redis.rb

@@ -22,17 +22,29 @@ module Patcher
               # For Rails >= 5.2 w/o redis-activesupport...
               # ActiveSupport includes a Redis cache store internally, and does not require these overrides.
               # https://github.com/rails/rails/blob/master/activesupport/lib/active_support/cache/redis_cache_store.rb
-              def patch_redis?(meth)
+              def patch_redis_activesupport?(meth)
                 !Gem.loaded_specs['redis-activesupport'].nil? \
                   && defined?(::ActiveSupport::Cache::RedisStore) \
                   && ::ActiveSupport::Cache::RedisStore.instance_methods(false).include?(meth)
               end
 
+              # Patches the Rails built-in Redis cache backend `redis_cache_store`, added in Rails 5.2.
+              # We avoid loading the RedisCacheStore class, as it invokes the statement `gem "redis", ">= 4.0.1"` which
+              # fails if the application is using an old version of Redis, or not using Redis at all.
+              # @see https://github.com/rails/rails/blob/d0dcb8fa6073a0c4d42600c15e82e3bb386b27d3/activesupport/lib/active_support/cache/redis_cache_store.rb#L4
+              def patch_redis_cache_store?(meth)
+                Gem.loaded_specs['redis'] &&
+                  # Autoload constants return `constant` for `defined?`, but that doesn't mean they are loaded...
+                  defined?(::ActiveSupport::Cache::RedisCacheStore) &&
+                  # ... to check that we need to call `autoload?` and check if it returns `nil`, meaning it's loaded.
+                  ::ActiveSupport::Cache.autoload?(:RedisCacheStore).nil? &&
+                  ::ActiveSupport::Cache::RedisCacheStore.instance_methods(false).include?(meth)
+              end
+
               def cache_store_class(meth)
-                if patch_redis?(meth)
+                if patch_redis_activesupport?(meth)
                   [::ActiveSupport::Cache::RedisStore, ::ActiveSupport::Cache::Store]
-                elsif Gem.loaded_specs['redis'] && defined?(::ActiveSupport::Cache::RedisCacheStore) \
-                    && ::ActiveSupport::Cache::RedisCacheStore.instance_methods(false).include?(meth)
+                elsif patch_redis_cache_store?(meth)
                   [::ActiveSupport::Cache::RedisCacheStore, ::ActiveSupport::Cache::Store]
                 else
                   super

sig/datadog/tracing/contrib/active_support/cache/patcher.rbs

@@ -10,7 +10,7 @@ module Datadog
 
             def self?.patch: () -> untyped
 
-            def self?.cache_store_class: (untyped meth) -> untyped
+            def self?.cache_store_class: (Symbol meth) -> Array[Class]
 
             def self?.patch_cache_store_read: () -> untyped
 

sig/datadog/tracing/contrib/active_support/cache/redis.rbs

@@ -5,9 +5,9 @@ module Datadog
         module Cache
           module Redis
             module Patcher
-              def patch_redis?: (untyped meth) -> untyped
-
-              def cache_store_class: (untyped meth) -> untyped
+              def patch_redis_activesupport?: (Symbol) -> bool
+              def patch_redis_cache_store?: (Symbol) -> bool
+              def cache_store_class: (Symbol) -> Array[Class]
             end
           end
         end