Allow nested and multiple fallbacks for generators.

railties/lib/generators.rb

@@ -162,11 +162,7 @@ def self.find_by_namespace(name, base=nil, context=nil) #:nodoc:
           base, name = name.split(':')
           return find_by_namespace(name, base)
         when 0
-          if base
-            base = base.to_sym
-            attempts << "#{base}:generators:#{name}"
-            attempts << "#{fallbacks[base]}:generators:#{name}" if fallbacks[base]
-          end
+          attempts << "#{base}:generators:#{name}"    if base
           attempts << "#{name}:generators:#{context}" if context
       end
 
@@ -179,7 +175,7 @@ def self.find_by_namespace(name, base=nil, context=nil) #:nodoc:
         return klass if klass
       end
 
-      nil
+      invoke_fallbacks_for(name, base)
     end
 
     # Receives a namespace, arguments and the behavior to invoke the generator.
@@ -242,6 +238,24 @@ def self.builtin #:nodoc:
         end
       end
 
+      # Try callbacks for the given base.
+      #
+      def self.invoke_fallbacks_for(name, base)
+        return nil unless base && fallbacks[base.to_sym]
+
+        invoked_fallbacks = []
+
+        Array(fallbacks[base.to_sym]).each do |fallback|
+          next if invoked_fallbacks.include?(fallback)
+          invoked_fallbacks << fallback
+
+          klass = find_by_namespace(name, fallback)
+          return klass if klass
+        end
+
+        nil
+      end
+
       # Receives namespaces in an array and tries to find matching generators
       # in the load path. Each path is traversed into directory lookups. For
       # example:

railties/test/generators_test.rb

@@ -116,16 +116,22 @@ def test_rails_root_templates
     rm_rf File.dirname(template)
   end
 
+  def test_fallbacks_for_generators_on_find_by_namespace
+    Rails::Generators.fallbacks[:remarkable] = :test_unit
+    klass = Rails::Generators.find_by_namespace(:plugin, :remarkable)
+    assert klass
+    assert_equal "test_unit:generators:plugin", klass.namespace
+  end
+
   def test_fallbacks_for_generators_on_invoke
     Rails::Generators.fallbacks[:shoulda] = :test_unit
     TestUnit::Generators::ModelGenerator.expects(:start).with(["Account"], {})
     Rails::Generators.invoke "shoulda:model", ["Account"]
   end
 
-  def test_fallbacks_for_generators_on_find_by_namespace
-    Rails::Generators.fallbacks[:remarkable] = :test_unit
-    klass = Rails::Generators.find_by_namespace(:plugin, :remarkable)
-    assert klass
-    assert_equal "test_unit:generators:plugin", klass.namespace
+  def test_nested_fallbacks_for_generators
+    Rails::Generators.fallbacks[:super_shoulda] = :shoulda
+    TestUnit::Generators::ModelGenerator.expects(:start).with(["Account"], {})
+    Rails::Generators.invoke "super_shoulda:model", ["Account"]
   end
 end