Move in code from RSpec::Mocks::RecursiveConstantMethods

lib/rspec/support/recursive_const_methods.rb

@@ -0,0 +1,77 @@
+module RSpec
+  module Support
+    # Provides recursive constant lookup methods useful for
+    # constant stubbing.
+    module RecursiveConstMethods
+      # We only want to consider constants that are defined directly on a
+      # particular module, and not include top-level/inherited constants.
+      # Unfortunately, the constant API changed between 1.8 and 1.9, so
+      # we need to conditionally define methods to ignore the top-level/inherited
+      # constants.
+      #
+      # Given:
+      #   class A; B = 1; end
+      #   class C < A; end
+      #
+      # On 1.8:
+      #   - C.const_get("Hash") # => ::Hash
+      #   - C.const_defined?("Hash") # => false
+      #   - C.constants # => ["B"]
+      #   - None of these methods accept the extra `inherit` argument
+      # On 1.9:
+      #   - C.const_get("Hash") # => ::Hash
+      #   - C.const_defined?("Hash") # => true
+      #   - C.const_get("Hash", false) # => raises NameError
+      #   - C.const_defined?("Hash", false) # => false
+      #   - C.constants # => [:B]
+      #   - C.constants(false) #=> []
+      if Module.method(:const_defined?).arity == 1
+        def const_defined_on?(mod, const_name)
+          mod.const_defined?(const_name)
+        end
+
+        def get_const_defined_on(mod, const_name)
+          if const_defined_on?(mod, const_name)
+            return mod.const_get(const_name)
+          end
+
+          raise NameError, "uninitialized constant #{mod.name}::#{const_name}"
+        end
+
+        def constants_defined_on(mod)
+          mod.constants.select { |c| const_defined_on?(mod, c) }
+        end
+      else
+        def const_defined_on?(mod, const_name)
+          mod.const_defined?(const_name, false)
+        end
+
+        def get_const_defined_on(mod, const_name)
+          mod.const_get(const_name, false)
+        end
+
+        def constants_defined_on(mod)
+          mod.constants(false)
+        end
+      end
+
+      def recursive_const_get(const_name)
+        normalize_const_name(const_name).split('::').inject(Object) do |mod, name|
+          get_const_defined_on(mod, name)
+        end
+      end
+
+      def recursive_const_defined?(const_name)
+        normalize_const_name(const_name).split('::').inject([Object, '']) do |(mod, full_name), name|
+          yield(full_name, name) if block_given? && !(Module === mod)
+          return false unless const_defined_on?(mod, name)
+          [get_const_defined_on(mod, name), [mod, name].join('::')]
+        end
+      end
+
+      def normalize_const_name(const_name)
+        const_name.sub(/\A::/, '')
+      end
+    end
+  end
+end

spec/rspec/support/recursive_const_methods_spec.rb

@@ -0,0 +1,50 @@
+require 'spec_helper'
+require 'rspec/support/recursive_const_methods'
+
+module RSpec
+  module Support
+    describe RecursiveConstMethods do
+      include described_class
+
+      module Foo
+        class Parent
+          UNDETECTED = 'Not seen when looking up constants in Bar'
+        end
+
+        class Bar < Parent
+          VAL = 10
+        end
+      end
+
+      describe '#recursive_const_defined?' do
+        it 'finds constants' do
+          const, _name = recursive_const_defined?('::RSpec::Support::Foo::Bar::VAL')
+
+          expect(const).to eq(10)
+        end
+
+        it 'returns the fully qualified name of the constant' do
+          _const, name = recursive_const_defined?('::RSpec::Support::Foo::Bar::VAL')
+
+          expect(name).to eq('RSpec::Support::Foo::Bar::VAL')
+        end
+
+        it 'does not find constants in ancestors' do
+          expect(recursive_const_defined?('::RSpec::Support::Foo::Bar::UNDETECTED')).to be_falsy
+        end
+      end
+
+      describe '#recursive_const_get' do
+        it 'gets constants' do
+          expect(recursive_const_get('::RSpec::Support::Foo::Bar::VAL')).to eq(10)
+        end
+
+        it 'does not get constants in ancestors' do
+          expect do
+            recursive_const_get('::RSpec::Support::Foo::Bar::UNDETECTED')
+          end.to raise_error(NameError)
+        end
+      end
+    end
+  end
+end