Let an app load ActionMailer/ActionView (#56)

* Let an app load ActionMailer/ActionView Requiring ActionMailer while the gem is loading might break initialization logic of a Rails app using Rails 6.0 or later. ActionMailer 6.0 introduces the new `delivery_job` setting (https://github.com/rails/rails/blob/6-0-stable/actionmailer/lib/action_mailer/railtie.rb#L49-L51) whose value is being constantized and applied as soon as ActionMailer is loaded. Normally, the delivery job would be configured during the app initialization, so if ActionMailer is loaded **before** the initializer is being executed, the configuration won’t be applied and a default `delivery_job` class would be used. The problem here is that Maildown is required before Rails initializers run, and it forces loading of ActionMailer by requiring `ActionMailer::Base` for monkey-patching. This causes ActionMailer to never apply `delivery_job` config. The solution seems simple enough: delay monkey-patching until ActionMailer is loaded. Because it's easy and seems safer, we'll also delay monkey-patching of ActionView until it's loaded as well. * Update CHANGELOG * Bump up verssions in Gemfiles Fix the CI build.
zombocom · Mar 17, 2021 · bde223a · bde223a
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 3.3.0
+
+- Delay loading of ActionMailer to fix support for `delivery_job` config (https://github.com/codetriage/maildown/pull/56)
+
 ## 3.2.0
 
 - Switch to "github style markdown" (https://github.com/codetriage/maildown/pull/54)

diff --git a/gemfiles/rails_5.gemfile.lock b/gemfiles/rails_5.gemfile.lock
@@ -1,7 +1,7 @@
 PATH
   remote: ..
   specs:
-    maildown (3.1.0)
+    maildown (3.2.0)
       actionmailer (>= 4.0.0)
       kramdown-parser-gfm
 
@@ -58,7 +58,7 @@ GEM
       activesupport (>= 4.2.0)
     i18n (1.6.0)
       concurrent-ruby (~> 1.0)
-    kramdown (2.2.1)
+    kramdown (2.3.0)
       rexml
     kramdown-parser-gfm (1.1.0)
       kramdown (~> 2.0)

diff --git a/gemfiles/rails_51.gemfile.lock b/gemfiles/rails_51.gemfile.lock
@@ -1,7 +1,7 @@
 PATH
   remote: ..
   specs:
-    maildown (3.1.0)
+    maildown (3.2.0)
       actionmailer (>= 4.0.0)
       kramdown-parser-gfm
 
@@ -58,7 +58,7 @@ GEM
       activesupport (>= 4.2.0)
     i18n (1.6.0)
       concurrent-ruby (~> 1.0)
-    kramdown (2.2.1)
+    kramdown (2.3.0)
       rexml
     kramdown-parser-gfm (1.1.0)
       kramdown (~> 2.0)

diff --git a/gemfiles/rails_52.gemfile.lock b/gemfiles/rails_52.gemfile.lock
@@ -1,7 +1,7 @@
 PATH
   remote: ..
   specs:
-    maildown (3.1.0)
+    maildown (3.2.0)
       actionmailer (>= 4.0.0)
       kramdown-parser-gfm
 
@@ -62,7 +62,7 @@ GEM
       activesupport (>= 4.2.0)
     i18n (1.6.0)
       concurrent-ruby (~> 1.0)
-    kramdown (2.2.1)
+    kramdown (2.3.0)
       rexml
     kramdown-parser-gfm (1.1.0)
       kramdown (~> 2.0)

diff --git a/gemfiles/rails_6.gemfile.lock b/gemfiles/rails_6.gemfile.lock
@@ -1,7 +1,7 @@
 PATH
   remote: ..
   specs:
-    maildown (3.1.0)
+    maildown (3.2.0)
       actionmailer (>= 4.0.0)
       kramdown-parser-gfm
 
@@ -75,7 +75,7 @@ GEM
       activesupport (>= 4.2.0)
     i18n (1.6.0)
       concurrent-ruby (~> 1.0)
-    kramdown (2.2.1)
+    kramdown (2.3.0)
       rexml
     kramdown-parser-gfm (1.1.0)
       kramdown (~> 2.0)

diff --git a/gemfiles/rails_head.gemfile.lock b/gemfiles/rails_head.gemfile.lock
@@ -82,7 +82,7 @@ GIT
 PATH
   remote: ..
   specs:
-    maildown (3.1.0)
+    maildown (3.2.0)
       actionmailer (>= 4.0.0)
       kramdown-parser-gfm
 
@@ -101,7 +101,7 @@ GEM
       activesupport (>= 4.2.0)
     i18n (1.6.0)
       concurrent-ruby (~> 1.0)
-    kramdown (2.2.1)
+    kramdown (2.3.0)
       rexml
     kramdown-parser-gfm (1.1.0)
       kramdown (~> 2.0)

diff --git a/lib/maildown.rb b/lib/maildown.rb
@@ -17,6 +17,10 @@ def self.rails_6?
 end
 
 require 'maildown/markdown_engine'
-require 'maildown/ext/action_mailer'
-require 'maildown/ext/action_view'
+ActiveSupport.on_load(:action_mailer) do
+  require 'maildown/ext/action_mailer'
+end
+ActiveSupport.on_load(:action_view) do
+  require 'maildown/ext/action_view'
+end
 require 'maildown/handlers/markdown'
diff --git a/lib/maildown/ext/action_mailer.rb b/lib/maildown/ext/action_mailer.rb
@@ -1,8 +1,5 @@
 # frozen_string_literal: true
 
-require 'action_mailer'
-require 'action_mailer/base'
-
 # Monkeypatch to allow mailer to auto generate text/html
 #
 # If you generate a mailer action, by default it will only

diff --git a/lib/maildown/ext/action_view.rb b/lib/maildown/ext/action_view.rb
@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require 'action_view'
-
 # This monkeypatch allows the use of `.md.erb` file extensions
 # in addition to `.md+erb` and `.md`
 module ActionView