Support objects that don't respond to #inspect in ObjectFormatter

```
[3] pry(main)> RSpec::Support::ObjectFormatter.format(BasicObject.new)
NoMethodError: undefined method `inspect' for #<BasicObject:0x007fb0252a5a08>
```

Author: yujinakayama

Changelog.md

@@ -1,6 +1,12 @@
 ### Development
 [Full Changelog](http://github.com/rspec/rspec-support/compare/v3.5.0.beta1...master)
 
+Bug Fixes:
+
+* Fix `ObjectFormatter` so that formatting objects that don't respond to
+  `#inspect` (such as `BasicObject`) does not cause `NoMethodError`.
+  (Yuji Nakayama, #269)
+
 ### 3.5.0.beta1 / 2016-02-06
 [Full Changelog](http://github.com/rspec/rspec-support/compare/v3.4.1...v3.5.0.beta1)
 

lib/rspec/support/object_formatter.rb

@@ -5,7 +5,7 @@ module Support
     # Provide additional output details beyond what `inspect` provides when
     # printing Time, DateTime, or BigDecimal
     # @api private
-    class ObjectFormatter
+    class ObjectFormatter # rubocop:disable ClassLength
       attr_accessor :max_formatted_output_length
 
       def initialize(max_formatted_output_length=200)
@@ -37,8 +37,6 @@ def self.format(object)
         @default_instance.format(object)
       end
 
-      # rubocop:disable MethodLength
-
       # Prepares the provided object to be formatted by wrapping it as needed
       # in something that, when `inspect` is called on it, will produce the
       # desired output.
@@ -48,7 +46,7 @@ def self.format(object)
       # with custom items that have `inspect` defined to return the desired output
       # for that item. Then we can just use `Array#inspect` or `Hash#inspect` to
       # format the entire thing.
-      def prepare_for_inspection(object)
+      def prepare_for_inspection(object) # rubocop:disable MethodLength, CyclomaticComplexity
         case object
         when Array
           return object.map { |o| prepare_for_inspection(o) }
@@ -61,6 +59,8 @@ def prepare_for_inspection(object)
             inspection = format_date_time(object)
           elsif defined?(BigDecimal) && BigDecimal === object
             inspection = "#{object.to_s 'F'} (#{object.inspect})"
+          elsif UninspectableObjectInspector.uninspectable_object?(object)
+            return UninspectableObjectInspector.new(object)
           elsif RSpec::Support.is_a_matcher?(object) && object.respond_to?(:description)
             inspection = object.description
           else
@@ -70,7 +70,6 @@ def prepare_for_inspection(object)
 
         InspectableItem.new(inspection)
       end
-      # rubocop:enable MethodLength
 
       def self.prepare_for_inspection(object)
         @default_instance.prepare_for_inspection(object)
@@ -141,6 +140,41 @@ def pretty_print(pp)
           pp.text inspect
         end
       end
+
+      UninspectableObjectInspector = Struct.new(:object) do
+        OBJECT_ID_FORMAT = '%#016x'
+
+        def self.uninspectable_object?(object)
+          object.inspect
+          false
+        rescue NoMethodError
+          true
+        end
+
+        # NoMethodError: undefined method `inspect' for #<BasicObject:0x007fe26d175140>
+        def inspect
+          "#<#{klass}:#{native_object_id}>"
+        end
+
+        def pretty_print(pp)
+          pp.text inspect
+        end
+
+        private
+
+        def klass
+          singleton_class = class << object; self; end
+          singleton_class.ancestors.find { |ancestor| !ancestor.equal?(singleton_class) }
+        end
+
+        # http://stackoverflow.com/a/2818916
+        def native_object_id
+          OBJECT_ID_FORMAT % (object.__id__ << 1)
+        rescue NoMethodError
+          # In Ruby 1.9.2, BasicObject responds to none of #__id__, #object_id, #id...
+          '-'
+        end
+      end
     end
   end
 end

spec/rspec/support/object_formatter_spec.rb

@@ -159,6 +159,40 @@ def with_delegate_loaded
         end
       end
 
+      context 'with an object that does not respond to #inspect such as BasicObject' do
+        subject(:output) do
+          ObjectFormatter.format(input)
+        end
+
+        let(:input) do
+          if defined?(BasicObject)
+            BasicObject.new
+          else
+            fake_basic_object_class.new
+          end
+        end
+
+        let(:fake_basic_object_class) do
+          Class.new do
+            def self.to_s
+              'BasicObject'
+            end
+
+            undef inspect, respond_to?
+          end
+        end
+
+        if RUBY_VERSION == '1.9.2'
+          it 'produces an #inspect-like output without object id' do
+            expect(output).to eq('#<BasicObject:->')
+          end
+        else
+          it "produces an output emulating MRI's #inspect-like output generated by C implementation" do
+            expect(output).to match(/\A#<BasicObject:0x[0-9a-f]{14}>\z/)
+          end
+        end
+      end
+
       context 'with truncation enabled' do
         it 'produces an output of limited length' do
           formatter = ObjectFormatter.new(10)