Allow nested and multiple fallbacks for generators.

railties/lib/generators.rb

@@ -162,11 +162,7 @@ module Rails
           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 @@ module Rails
         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 @@ module Rails
         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 @@ class GeneratorsTest < GeneratorsTestCase
     rm_rf File.dirname(template)
   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
   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_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