From 7b6b10542d5dac2b50f2578143dc5d70120d1146 Mon Sep 17 00:00:00 2001
From: Xavier Noria <fxn@hashref.com>
Date: Thu, 11 Apr 2019 22:43:45 +0200
Subject: improves the reloading disabled error message

The original message from Zeitwerk is "can't reload, please call
loader.enable_reloading before setup (Zeitwerk::Error)", which is not
very informative for Rails programmers.

Rails should err with a message worded in terms of its interface.
---
 Gemfile.lock                                                     | 4 ++--
 activesupport/activesupport.gemspec                              | 2 +-
 .../lib/active_support/dependencies/zeitwerk_integration.rb      | 6 +++++-
 railties/test/application/zeitwerk_integration_test.rb           | 9 +++++++++
 4 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/Gemfile.lock b/Gemfile.lock
index 8e219f3f31..b92603d799 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -71,7 +71,7 @@ PATH
       i18n (>= 0.7, < 2)
       minitest (~> 5.1)
       tzinfo (~> 1.1)
-      zeitwerk (~> 2.1)
+      zeitwerk (~> 2.1, >= 2.1.2)
     rails (6.0.0.beta3)
       actioncable (= 6.0.0.beta3)
       actionmailbox (= 6.0.0.beta3)
@@ -526,7 +526,7 @@ GEM
     websocket-extensions (0.1.3)
     xpath (3.2.0)
       nokogiri (~> 1.8)
-    zeitwerk (2.1.0)
+    zeitwerk (2.1.2)
 
 PLATFORMS
   java
diff --git a/activesupport/activesupport.gemspec b/activesupport/activesupport.gemspec
index 546cc1797a..dd2340cdd3 100644
--- a/activesupport/activesupport.gemspec
+++ b/activesupport/activesupport.gemspec
@@ -34,5 +34,5 @@ Gem::Specification.new do |s|
   s.add_dependency "tzinfo",          "~> 1.1"
   s.add_dependency "minitest",        "~> 5.1"
   s.add_dependency "concurrent-ruby", "~> 1.0", ">= 1.0.2"
-  s.add_dependency "zeitwerk",        "~> 2.1"
+  s.add_dependency "zeitwerk",        "~> 2.1", ">= 2.1.2"
 end
diff --git a/activesupport/lib/active_support/dependencies/zeitwerk_integration.rb b/activesupport/lib/active_support/dependencies/zeitwerk_integration.rb
index b0f7a3f9cc..f16a9f7e57 100644
--- a/activesupport/lib/active_support/dependencies/zeitwerk_integration.rb
+++ b/activesupport/lib/active_support/dependencies/zeitwerk_integration.rb
@@ -9,7 +9,11 @@ module ActiveSupport
       module Decorations
         def clear
           Dependencies.unload_interlock do
-            Rails.autoloaders.main.reload
+            begin
+              Rails.autoloaders.main.reload
+            rescue Zeitwerk::ReloadingDisabledError
+              raise "reloading is disabled because config.cache_classes is true"
+            end
           end
         end
 
diff --git a/railties/test/application/zeitwerk_integration_test.rb b/railties/test/application/zeitwerk_integration_test.rb
index b248459e47..40d06ee999 100644
--- a/railties/test/application/zeitwerk_integration_test.rb
+++ b/railties/test/application/zeitwerk_integration_test.rb
@@ -156,6 +156,15 @@ class ZeitwerkIntegrationTest < ActiveSupport::TestCase
     assert_not Rails.autoloaders.once.reloading_enabled?
   end
 
+  test "reloading raises if config.cache_classes is true" do
+    boot("production")
+
+    e = assert_raises(StandardError) do
+      deps.clear
+    end
+    assert_equal "reloading is disabled because config.cache_classes is true", e.message
+  end
+
   test "eager loading loads code in engines" do
     $test_blog_engine_eager_loaded = false
 
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