Added ActiveSupport::Inflector.safe_constantize and String#safe_constantize; refactored common constantize tests into ConstantizeTestCases

activesupport/lib/active_support/core_ext/string/inflections.rb

@@ -33,14 +33,27 @@ class String
 
   # +constantize+ tries to find a declared constant with the name specified
   # in the string. It raises a NameError when the name is not in CamelCase
-  # or is not initialized.
+  # or is not initialized.  See ActiveSupport::Inflector.constantize
   #
   # Examples
-  #   "Module".constantize # => Module
-  #   "Class".constantize  # => Class
+  #   "Module".constantize       # => Module
+  #   "Class".constantize        # => Class
+  #   "blargle".safe_constantize # => NameError: wrong constant name blargle
   def constantize
     ActiveSupport::Inflector.constantize(self)
   end
+  
+  # +safe_constantize+ tries to find a declared constant with the name specified
+  # in the string. It returns nil when the name is not in CamelCase
+  # or is not initialized.  See ActiveSupport::Inflector.safe_constantize
+  #
+  # Examples
+  #   "Module".safe_constantize  # => Module
+  #   "Class".safe_constantize   # => Class
+  #   "blargle".safe_constantize # => nil
+  def safe_constantize
+    ActiveSupport::Inflector.safe_constantize(self)
+  end
 
   # By default, +camelize+ converts strings to UpperCamelCase. If the argument to camelize
   # is set to <tt>:lower</tt> then camelize produces lowerCamelCase.

activesupport/lib/active_support/inflector/methods.rb

@@ -224,6 +224,33 @@ module ActiveSupport
       end
     end
 
+    # Tries to find a constant with the name specified in the argument string:
+    #
+    #   "Module".safe_constantize     # => Module
+    #   "Test::Unit".safe_constantize # => Test::Unit
+    #
+    # The name is assumed to be the one of a top-level constant, no matter whether
+    # it starts with "::" or not. No lexical context is taken into account:
+    #
+    #   C = 'outside'
+    #   module M
+    #     C = 'inside'
+    #     C                    # => 'inside'
+    #     "C".safe_constantize # => 'outside', same as ::C
+    #   end
+    #
+    # nil is returned when the name is not in CamelCase or the constant is
+    # unknown.
+    #
+    #   "blargle".safe_constantize  # => nil
+    def safe_constantize(camel_cased_word)
+      begin
+        camel_cased_word.constantize
+      rescue NameError
+        nil
+      end
+    end
+    
     # Turns a number into an ordinal string used to denote the position in an
     # ordered sequence such as 1st, 2nd, 3rd, 4th.
     #

activesupport/test/constantize_test_cases.rb

@@ -0,0 +1,31 @@
+module Ace
+  module Base
+    class Case
+    end
+  end
+end
+
+module ConstantizeTestCases
+  def run_constantize_tests_on
+    assert_nothing_raised { assert_equal Ace::Base::Case, yield("Ace::Base::Case") }
+    assert_nothing_raised { assert_equal Ace::Base::Case, yield("::Ace::Base::Case") }
+    assert_nothing_raised { assert_equal ConstantizeTestCases, yield("ConstantizeTestCases") }
+    assert_nothing_raised { assert_equal ConstantizeTestCases, yield("::ConstantizeTestCases") }
+    assert_raise(NameError) { yield("UnknownClass") }
+    assert_raise(NameError) { yield("An invalid string") }
+    assert_raise(NameError) { yield("InvalidClass\n") }
+    assert_raise(NameError) { yield("Ace::Base::ConstantizeTestCases") }
+  end
+  
+  def run_safe_constantize_tests_on
+    assert_nothing_raised { assert_equal Ace::Base::Case, yield("Ace::Base::Case") }
+    assert_nothing_raised { assert_equal Ace::Base::Case, yield("::Ace::Base::Case") }
+    assert_nothing_raised { assert_equal ConstantizeTestCases, yield("ConstantizeTestCases") }
+    assert_nothing_raised { assert_equal ConstantizeTestCases, yield("::ConstantizeTestCases") }
+    assert_nothing_raised { assert_equal nil, yield("UnknownClass") }
+    assert_nothing_raised { assert_equal nil, yield("An invalid string") }
+    assert_nothing_raised { assert_equal nil, yield("InvalidClass\n") }
+    assert_nothing_raised { assert_equal nil, yield("blargle") }
+    assert_nothing_raised { assert_equal nil, yield("Ace::Base::ConstantizeTestCases") }
+  end
+end

activesupport/test/core_ext/string_ext_test.rb

@@ -2,6 +2,7 @@
 require 'date'
 require 'abstract_unit'
 require 'inflector_test_cases'
+require 'constantize_test_cases'
 
 require 'active_support/inflector'
 require 'active_support/core_ext/string'
@@ -9,9 +10,17 @@ require 'active_support/time'
 require 'active_support/core_ext/string/strip'
 require 'active_support/core_ext/string/output_safety'
 
+module Ace
+  module Base
+    class Case
+    end
+  end
+end
+
 class StringInflectionsTest < Test::Unit::TestCase
   include InflectorTestCases
-
+  include ConstantizeTestCases
+  
   def test_erb_escape
     string = [192, 60].pack('CC')
     expected = 192.chr + "&lt;"
@@ -292,6 +301,18 @@ class StringInflectionsTest < Test::Unit::TestCase
         "\354\225\204\353\246\254\353\236\221 \354\225\204\353\246\254 \354\225\204\353\235\274\353\246\254\354\230\244".force_encoding('UTF-8').truncate(10)
     end
   end
+  
+  def test_constantize
+    run_constantize_tests_on do |string|
+      string.constantize
+    end
+  end
+  
+  def test_safe_constantize
+    run_safe_constantize_tests_on do |string|
+      string.safe_constantize
+    end
+  end
 end
 
 class StringBehaviourTest < Test::Unit::TestCase

activesupport/test/inflector_test.rb

@@ -2,16 +2,11 @@ require 'abstract_unit'
 require 'active_support/inflector'
 
 require 'inflector_test_cases'
-
-module Ace
-  module Base
-    class Case
-    end
-  end
-end
+require 'constantize_test_cases'
 
 class InflectorTest < Test::Unit::TestCase
   include InflectorTestCases
+  include ConstantizeTestCases
 
   def test_pluralize_plurals
     assert_equal "plurals", ActiveSupport::Inflector.pluralize("plurals")
@@ -282,17 +277,15 @@ class InflectorTest < Test::Unit::TestCase
   end
 
   def test_constantize
-    assert_nothing_raised { assert_equal Ace::Base::Case, ActiveSupport::Inflector.constantize("Ace::Base::Case") }
-    assert_nothing_raised { assert_equal Ace::Base::Case, ActiveSupport::Inflector.constantize("::Ace::Base::Case") }
-    assert_nothing_raised { assert_equal InflectorTest, ActiveSupport::Inflector.constantize("InflectorTest") }
-    assert_nothing_raised { assert_equal InflectorTest, ActiveSupport::Inflector.constantize("::InflectorTest") }
-    assert_raise(NameError) { ActiveSupport::Inflector.constantize("UnknownClass") }
-    assert_raise(NameError) { ActiveSupport::Inflector.constantize("An invalid string") }
-    assert_raise(NameError) { ActiveSupport::Inflector.constantize("InvalidClass\n") }
+    run_constantize_tests_on do |string|
+      ActiveSupport::Inflector.constantize(string)
+    end
   end
-
-  def test_constantize_does_lexical_lookup
-    assert_raise(NameError) { ActiveSupport::Inflector.constantize("Ace::Base::InflectorTest") }
+  
+  def test_safe_constantize
+    run_safe_constantize_tests_on do |string|
+      ActiveSupport::Inflector.safe_constantize(string)
+    end
   end
 
   def test_ordinal