Add safe_constantize to ActiveSupport::Dependencies.

activesupport/lib/active_support/dependencies.rb

@@ -527,7 +527,7 @@ module ActiveSupport #:nodoc:
 
     class ClassCache
       def initialize
-        @store = Hash.new { |h, k| h[k] = Inflector.constantize(k) }
+        @store = Hash.new
       end
 
       def empty?
@@ -538,23 +538,23 @@ module ActiveSupport #:nodoc:
         @store.key?(key)
       end
 
-      def []=(key, value)
+      def get(key)
-        return unless key.respond_to?(:name)
-
-        raise(ArgumentError, 'anonymous classes cannot be cached') if key.name.blank?
-
-        @store[key.name] = value
-      end
-
-      def [](key)
         key = key.name if key.respond_to?(:name)
-
+        @store[key] ||= Inflector.constantize(key)
-        @store[key]
       end
-      alias :get :[]
 
-      def store(name)
+      def safe_get(key)
-        self[name] = name
+        key = key.name if key.respond_to?(:name)
+        @store[key] || begin
+          klass = Inflector.safe_constantize(key)
+          @store[key] = klass
+        end
+      end
+
+      def store(klass)
+        return self unless klass.respond_to?(:name)
+        raise(ArgumentError, 'anonymous classes cannot be cached') if klass.name.empty?
+        @store[klass.name] = klass
         self
       end
 
@@ -571,10 +571,17 @@ module ActiveSupport #:nodoc:
     end
 
     # Get the reference for class named +name+.
+    # Raises an exception if referenced class does not exist.
     def constantize(name)
       Reference.get(name)
     end
 
+    # Get the reference for class named +name+ if one exists.
+    # Otherwise returns nil.
+    def safe_constantize(name)
+      Reference.safe_get(name)
+    end
+
     # Determine if the given constant has been automatically loaded.
     def autoloaded?(desc)
       # No name => anonymous module.

activesupport/test/class_cache_test.rb

@@ -10,45 +10,53 @@ module ActiveSupport
 
       def test_empty?
         assert @cache.empty?
-        @cache[ClassCacheTest] = ClassCacheTest
+        @cache.store(ClassCacheTest)
         assert !@cache.empty?
       end
 
       def test_clear!
         assert @cache.empty?
-        @cache[ClassCacheTest] = ClassCacheTest
+        @cache.store(ClassCacheTest)
         assert !@cache.empty?
         @cache.clear!
         assert @cache.empty?
       end
 
       def test_set_key
-        @cache[ClassCacheTest] = ClassCacheTest
+        @cache.store(ClassCacheTest)
         assert @cache.key?(ClassCacheTest.name)
       end
 
-      def test_set_rejects_strings
-        @cache[ClassCacheTest.name] = ClassCacheTest
-        assert @cache.empty?
-      end
-
       def test_get_with_class
-        @cache[ClassCacheTest] = ClassCacheTest
+        @cache.store(ClassCacheTest)
-        assert_equal ClassCacheTest, @cache[ClassCacheTest]
+        assert_equal ClassCacheTest, @cache.get(ClassCacheTest)
       end
 
       def test_get_with_name
-        @cache[ClassCacheTest] = ClassCacheTest
+        @cache.store(ClassCacheTest)
-        assert_equal ClassCacheTest, @cache[ClassCacheTest.name]
+        assert_equal ClassCacheTest, @cache.get(ClassCacheTest.name)
       end
 
       def test_get_constantizes
         assert @cache.empty?
-        assert_equal ClassCacheTest, @cache[ClassCacheTest.name]
+        assert_equal ClassCacheTest, @cache.get(ClassCacheTest.name)
       end
 
-      def test_get_is_an_alias
+      def test_get_constantizes_fails_on_invalid_names
-        assert_equal @cache[ClassCacheTest], @cache.get(ClassCacheTest.name)
+        assert @cache.empty?
+        assert_raise NameError do
+          @cache.get("OmgTotallyInvalidConstantName")
+        end
+      end
+
+      def test_safe_get_constantizes
+        assert @cache.empty?
+        assert_equal ClassCacheTest, @cache.safe_get(ClassCacheTest.name)
+      end
+
+      def test_safe_get_constantizes_doesnt_fail_on_invalid_names
+        assert @cache.empty?
+        assert_equal nil, @cache.safe_get("OmgTotallyInvalidConstantName")
       end
 
       def test_new_rejects_strings