1 files changed, 22 insertions, 12 deletions
diff --git a/railties/lib/rails/api/task.rb b/railties/lib/rails/api/task.rb
index 3e7223f075..1e6458cf93 100644
--- a/railties/lib/rails/api/task.rb
+++ b/railties/lib/rails/api/task.rb
@@ -64,17 +64,12 @@ module Rails
       def initialize(name)
         super
 
-        self.title    = 'Ruby on Rails API'
-        self.rdoc_dir = api_dir
-
-        options << '-m'  << api_main
-        options << '-e'  << 'UTF-8'
-        options << '-f'  << 'sdoc'
-        options << '-T'  << 'rails'
-
-        configure_rdoc_files
-
+        # Every time rake runs this task is instantiated as all the rest.
+        # Be lazy computing stuff to have as light impact as possible to
+        # the rest of tasks.
         before_running_rdoc do
+          load_and_configure_sdoc
+          configure_rdoc_files
           setup_horo_variables
         end
       end
@@ -84,6 +79,22 @@ module Rails
         # no-op
       end
 
+      def load_and_configure_sdoc
+        require 'sdoc'
+
+        self.title    = 'Ruby on Rails API'
+        self.rdoc_dir = api_dir
+
+        options << '-m'  << api_main
+        options << '-e'  << 'UTF-8'
+
+        options << '-f'  << 'sdoc'
+        options << '-T'  << 'rails'
+      rescue LoadError
+        $stderr.puts %(Unable to load SDoc, please add\n\n    gem 'sdoc', require: false\n\nto the Gemfile.)
+        exit 1
+      end
+
       def configure_rdoc_files
         rdoc_files.include(api_main)
 
@@ -111,9 +122,8 @@ module Rails
     end
 
     class RepoTask < Task
-      def initialize(name)
+      def load_and_configure_sdoc
         super
-
         options << '-g' # link to GitHub, SDoc flag
       end