Make BeBetween composable

lib/rspec/matchers.rb

@@ -330,6 +330,7 @@ def be_a_kind_of(expected)
     def be_between(min, max)
       BuiltIn::BeBetween.new(min, max)
     end
+    alias_matcher :a_value_between, :be_between
 
     # Passes if actual == expected +/- delta
     #

lib/rspec/matchers/built_in/be_between.rb

@@ -2,18 +2,38 @@ module RSpec
   module Matchers
     module BuiltIn
       class BeBetween < BaseMatcher
+        include Composable
+
         def initialize(min, max)
           @min, @max = min, max
         end
 
         def matches?(actual)
           @actual = actual
-          @actual.between?(@min, @max)
+          comparable? and @actual.between?(@min, @max)
+        end
+
+        def failure_message
+          "expected #{@actual.inspect} to #{description}#{not_comparable_clause}"
+        end
+
+        def failure_message_when_negated
+          "expected #{@actual.inspect} not to #{description}"
         end
 
         def description
           "be between #{@min.inspect} and #{@max.inspect} (inclusive)"
         end
+
+      private
+
+        def comparable?
+          @actual.respond_to?(:between?)
+        end
+
+        def not_comparable_clause
+          ", but #{@actual.inspect} does not respond to `between?`" unless comparable?
+        end
       end
     end
   end

lib/rspec/matchers/built_in/be_within.rb

@@ -33,7 +33,7 @@ def failure_message
         end
 
         def failure_message_when_negated
-          "expected #{@actual} not to #{description}"
+          "expected #{@actual.inspect} not to #{description}"
         end
 
         def description
@@ -51,8 +51,7 @@ def needs_expected
         end
 
         def not_numeric_clause
-          return "" if numeric?
-          ", but it could not be treated as a numeric value"
+          ", but it could not be treated as a numeric value" unless numeric?
         end
       end
     end

spec/rspec/matchers/aliases_spec.rb

@@ -80,6 +80,14 @@ module RSpec
       ).with_description("a kind of Integer")
     end
 
+    specify do
+      expect(
+        a_value_between(1, 10)
+      ).to be_aliased_to(
+        be_between(1, 10)
+      ).with_description("a value between 1 and 10 (inclusive)")
+    end
+
     specify do
       expect(
         a_value_within(0.1).of(3)

spec/rspec/matchers/built_in/be_between_spec.rb

@@ -55,3 +55,20 @@ def inspect
     }.to fail_with("expected 10 not to be between 1 and 10 (inclusive)")
   end
 end
+
+describe "composing with other matchers" do
+  it "passes when the matchers both match" do
+    expect([0.1, 2]).to include(a_value_between(2, 4), an_instance_of(Float))
+  end
+
+  it "provides a description" do
+    description = include(a_value_between(2, 4), an_instance_of(Float)).description
+    expect(description).to eq("include (a value between 2 and 4 (inclusive)) and (an instance of Float)")
+  end
+
+  it "fails with a clear error message when the matchers do not match" do
+    expect {
+      expect([0.1, 1]).to include(a_value_between(2, 4), an_instance_of(Float))
+    }.to fail_with("expected [0.1, 1] to include (a value between 2 and 4 (inclusive)) and (an instance of Float)")
+  end
+end