Expose broken ActionMailer preview setup.

This fixes the spec suite to expose issues with `ActionMailer` being
configured incorrectly when previews are not available.

This addresses several issues:

- The incorrect configuration options are only exposed once
  `ActionMailer::Base` is loaded; this forces the class to load in the
  mailer initializer and at the end of our script
- This adds specs specifically for the "development" environment which
  were missing before; it appeared that by not setting the environment
  it would default to "development" per the script, however, when the
  command shells out the `RAILS_ENV` is already set to "test" from rspec
  running.

  To be certain we cover the other possible edge cases we specifically
  add more tests for `ActionMailer` not being available, and for a
  custom configuration being set after `rspec-rails` is loaded.
- Despite us asking Rails to turn off eager loading in our custom
  script, several files were still getting eager loaded; this
  explicitly clears the eager load paths to stop this
- This fixes how the mailer script is shelled out in Ruby 1.8.7; now the
  environment variables are properly formatted and standard error is
  piped to standard out

Exposes the regression issue in #1386

Author: cupakromer

example_app_generator/generate_action_mailer_specs.rb

@@ -14,11 +14,25 @@ def comment_lines(path, flag, *args)
 
   initializer 'action_mailer.rb', <<-CODE
     if ENV['DEFAULT_URL']
-      Rails.application.configure do
-        config.action_mailer.default_url_options = { :host => ENV['DEFAULT_URL'] }
+      if ::Rails::VERSION::STRING < '4.1'
+        ExampleApp::Application.configure do
+          config.action_mailer.default_url_options = { :host => ENV['DEFAULT_URL'] }
+        end
+      else
+        Rails.application.configure do
+          config.action_mailer.default_url_options = { :host => ENV['DEFAULT_URL'] }
+        end
       end
     end
+
+    if defined?(ActionMailer)
+      # This will force the loading of ActionMailer settings
+      ActionMailer::Base.smtp_settings
+    end
   CODE
+  gsub_file 'config/initializers/action_mailer.rb',
+            /ExampleApp/,
+            Rails.application.class.parent.to_s
 
   copy_file 'spec/support/default_preview_path'
   chmod 'spec/support/default_preview_path', 0755

example_app_generator/spec/support/default_preview_path

@@ -32,6 +32,7 @@ require_file_stub 'config/environment' do
     module ExampleApp
       class Application < Rails::Application
         config.eager_load = false
+        config.eager_load_paths.clear
 
         # Don't care if the mailer can't send.
         config.action_mailer.raise_delivery_errors = false unless ENV['NO_ACTION_MAILER']
@@ -58,3 +59,7 @@ if ENV['DEFAULT_URL']
 elsif defined?(::ActionMailer::Preview)
   puts Rails.application.config.action_mailer.preview_path
 end
+
+# This will force the loading of ActionMailer settings to ensure we do not
+# accicentally set something we should not
+ActionMailer::Base.smtp_settings

example_app_generator/spec/verify_mailer_preview_path_spec.rb

@@ -8,17 +8,25 @@ def ==(str)
     end
   end
 
+  def as_commandline(ops)
+    cmd, ops = ops.reverse
+    ops ||= {}
+    cmd_parts = ops.map { |k, v| "#{k}=#{v}" } << cmd << '2>&1'
+    cmd_parts.join(' ')
+  end
+
   def capture_exec(*ops)
     io = if RUBY_VERSION.to_f < 1.9
-           IO.popen(ops.join(' '))
+           IO.popen(as_commandline(ops))
          else
            ops << { :err => [:child, :out] }
            IO.popen(ops)
          end
     # Necessary to ignore warnings from Rails code base
-    out =  io.readlines.reject { |line|
-      line =~ /warning: circular argument reference/
-    }.join.chomp
+    out =  io.readlines.
+              reject { |line| line =~ /warning: circular argument reference/ }.
+              join.
+              chomp
     CaptureExec.new(out, $?.exitstatus)
   end
 
@@ -176,8 +184,58 @@ def have_no_preview
       end
     end
   else
-    it 'handles no action mailer preview' do
-      expect(capture_exec(exec_script)).to have_no_preview
+    context 'in the development environment' do
+      let(:custom_env) { { 'RAILS_ENV' => rails_env } }
+      let(:rails_env) { 'development' }
+
+      it 'handles no action mailer preview' do
+        expect(capture_exec(custom_env, exec_script)).to have_no_preview
+      end
+
+      it 'allows initializers to set options' do
+        expect(
+          capture_exec(
+            custom_env.merge('DEFAULT_URL' => 'test-host'),
+            exec_script
+          )
+        ).to eq('test-host')
+      end
+
+      it 'handles action mailer not being available' do
+        expect(
+          capture_exec(
+            custom_env.merge('NO_ACTION_MAILER' => 'true'),
+            exec_script
+          )
+        ).to have_no_preview
+      end
+    end
+
+    context 'in a non-development environment' do
+      let(:custom_env) { { 'RAILS_ENV' => rails_env } }
+      let(:rails_env) { 'test' }
+
+      it 'handles no action mailer preview' do
+        expect(capture_exec(custom_env, exec_script)).to have_no_preview
+      end
+
+      it 'allows initializers to set options' do
+        expect(
+          capture_exec(
+            custom_env.merge('DEFAULT_URL' => 'test-host'),
+            exec_script
+          )
+        ).to eq('test-host')
+      end
+
+      it 'handles action mailer not being available' do
+        expect(
+          capture_exec(
+            custom_env.merge('NO_ACTION_MAILER' => 'true'),
+            exec_script
+          )
+        ).to have_no_preview
+      end
     end
   end
 end