Assign the matcher subclass to a human readable const.

This helps provides useful `#inspect` output.

features/custom_matchers/access_running_example.feature

@@ -49,5 +49,5 @@ Feature: access running example
     When I run `rspec ./example_spec.rb`
     Then the output should contain "1 example, 1 failure"
     And the output should match /undefined.*method/
-    And the output should contain "RSpec::Matchers::DSL::Matcher"
+    And the output should contain "RSpec::Matchers::Custom::Bar"
     And the output should not contain "ExampleGroup"

lib/rspec/matchers/matcher.rb

@@ -219,12 +219,10 @@ def initialize(*expected)
           @expected = expected
         end
 
-        # Needed so the matcher is easily identifier in error messages.
-        # Without this, ruby's default instance-of-an-anonymous-class
-        # #inspect would be used (which looks like
-        # `#<#<Class:0x007fca1505c4e0>:0x007fca1505c468>`)
+        # Adds the expected value so we can identify an instance of
+        # the matcher in error messages (e.g. for `NoMethodError`)
         def inspect
-          "#<RSpec::Matchers::DSL::Matcher (#{name})>"
+          "#<#{self.class.name} expected=#{expected}>"
         end
 
         # Indicates that this matcher responds to messages
@@ -266,9 +264,27 @@ def self.subclass(name, &declarations)
           Class.new(self) do
             define_method(:name) { name }
             @declarations = declarations
+          end.tap do |klass|
+            const_name = ('_' + name.to_s).gsub(/_+([[:alpha:]])/) { $1.upcase }
+
+            # Constants must start with [A-Z]
+            const_name.gsub!(/\A_+/, '')          # Remove any leading underscores
+            const_name.gsub!(/\A([^A-Z])/, 'A\1') # Prepend a valid first letter if needed
+
+            # Add a trailing number if needed to disambiguate from an existing constant.
+            if Custom.const_defined?(const_name)
+              const_name << "2"
+              const_name.next! while Custom.const_defined?(const_name)
+            end
+
+            Custom.const_set(const_name, klass)
           end
         end
       end
     end
+
+    # Namespace module that holds custom matcher classes.
+    module Custom
+    end
   end
 end

spec/rspec/matchers/matcher_spec.rb

@@ -1,3 +1,4 @@
+# encoding: utf-8
 require 'spec_helper'
 
 class UnexpectedError < StandardError; end
@@ -41,6 +42,49 @@ def new_matcher(name, *expected, &block)
       expect(m2.matches?(2)).to be_truthy
     end
 
+    describe "constant assignment" do
+      it 'gets assigned to a human readable constant' do
+        matcher = new_matcher(:be_a_something) { }
+        expect(matcher).to be_a(RSpec::Matchers::Custom::BeASomething)
+      end
+
+      it 'assigns a constant even when there are extra leading underscores' do
+        matcher = new_matcher(:__foo__bar__) { }
+        expect(matcher).to be_a(RSpec::Matchers::Custom::FooBar__)
+      end
+
+      it 'differentiates redefinitions by appending a number' do
+        m1 = new_matcher(:foo_redef) { }
+        m2 = new_matcher(:foo_redef) { }
+        m3 = new_matcher(:foo_redef) { }
+
+        expect(m1).to be_a(RSpec::Matchers::Custom::FooRedef)
+        expect(m2).to be_a(RSpec::Matchers::Custom::FooRedef2)
+        expect(m3).to be_a(RSpec::Matchers::Custom::FooRedef3)
+      end
+
+      it 'supports non-ascii characters', :if => (RUBY_VERSION.to_f > 1.8) do
+        # We have to eval this because 1.8.7 can't parse it at file load time
+        # if we don't eval it. eval delays when it is parsed until the example
+        # is run, which does not happen on 1.8.7
+        eval <<-EOS
+          RSpec::Matchers.define(:们) { }
+          expect(们).to be_a(RSpec::Matchers::Custom::A们)
+
+          RSpec::Matchers.define(:be_们) { }
+          expect(be_们).to be_a(RSpec::Matchers::Custom::Be们)
+        EOS
+      end
+
+      it 'handles the case where the matcher name starts with a capitol letter' do
+        matcher = new_matcher(:Capitol_letter) { }
+        expect(matcher).to be_a(RSpec::Matchers::Custom::CapitolLetter)
+
+        matcher = new_matcher(:__Capitol_prefixed_by_underscores) { }
+        expect(matcher.inspect).to include('CapitolPrefixedByUnderscores')
+      end
+    end
+
     context "with an included module" do
       let(:matcher) do
         new_matcher(:be_a_greeting) do
@@ -595,7 +639,7 @@ def a_method_in_the_example
 
         expect {
           expect(example).to __raise_no_method_error
-        }.to raise_error(NoMethodError, /RSpec::Matchers::DSL::Matcher/)
+        }.to raise_error(NoMethodError, /RSpec::Matchers::Custom::RaiseNoMethodError/)
       end
     end