Add ability to inspect all describable matchers (#219)

In a previous commit, a new inspection tree builder was added which was
designed to handle built-in RSpec matchers as well as matchers created
via the matcher DSL, by reusing the `description` of the matcher as the
inspection text. However, this inspector did not cover custom matchers
defined from scratch rather than via the DSL. This commit corrects this
by making use of the `is_a_describable_matcher?` method from
RSpec::Matchers.

lib/super_diff/rspec.rb

@@ -113,7 +113,7 @@ def self.rspec_version
         ObjectInspection::InspectionTreeBuilders::ObjectHavingAttributes,
         # ObjectInspection::InspectionTreeBuilders::Primitive,
         ObjectInspection::InspectionTreeBuilders::ValueWithin,
-        ObjectInspection::InspectionTreeBuilders::RSpecMatcher
+        ObjectInspection::InspectionTreeBuilders::GenericDescribableMatcher
       )
     end
   end

lib/super_diff/rspec/object_inspection/inspection_tree_builders.rb

@@ -14,6 +14,10 @@ module InspectionTreeBuilders
           :Double,
           "super_diff/rspec/object_inspection/inspection_tree_builders/double"
         )
+        autoload(
+          :GenericDescribableMatcher,
+          "super_diff/rspec/object_inspection/inspection_tree_builders/generic_describable_matcher"
+        )
         autoload(
           :HashIncluding,
           "super_diff/rspec/object_inspection/inspection_tree_builders/hash_including"
@@ -34,10 +38,6 @@ module InspectionTreeBuilders
           :Primitive,
           "super_diff/rspec/object_inspection/inspection_tree_builders/primitive"
         )
-        autoload(
-          :RSpecMatcher,
-          "super_diff/rspec/object_inspection/inspection_tree_builders/rspec_matcher"
-        )
         autoload(
           :ValueWithin,
           "super_diff/rspec/object_inspection/inspection_tree_builders/value_within"

lib/super_diff/rspec/object_inspection/inspection_tree_builders/rspec_matcher.rb → lib/super_diff/rspec/object_inspection/inspection_tree_builders/generic_describable_matcher.rb

@@ -2,10 +2,9 @@ module SuperDiff
   module RSpec
     module ObjectInspection
       module InspectionTreeBuilders
-        class RSpecMatcher < SuperDiff::ObjectInspection::InspectionTreeBuilders::Base
+        class GenericDescribableMatcher < SuperDiff::ObjectInspection::InspectionTreeBuilders::Base
           def self.applies_to?(value)
-            value.is_a?(::RSpec::Matchers::BuiltIn::BaseMatcher) ||
-              value.is_a?(::RSpec::Matchers::DSL::Matcher)
+            ::RSpec::Matchers.is_a_describable_matcher?(value)
           end
 
           def call

spec/integration/rspec/generic_describable_matchers_spec.rb

@@ -0,0 +1,177 @@
+require "spec_helper"
+
+RSpec.describe "Integration with describable matchers not handled specially",
+               type: :integration do
+  context "when the expected value contains a built-in matcher (not an aliased matcher)" do
+    it "produces the correct failure message when used in the positive" do
+      as_both_colored_and_uncolored do |color_enabled|
+        snippet = <<~TEST.strip
+            actual = {
+              number: "not a number"
+            }
+            expected = hash_including(
+              number: be_a(Numeric)
+            )
+            expect(actual).to match(expected)
+        TEST
+        program = make_plain_test_program(snippet, color_enabled: color_enabled)
+
+        expected_output =
+          build_expected_output(
+            color_enabled: color_enabled,
+            snippet: "expect(actual).to match(expected)",
+            expectation:
+              proc do
+                line do
+                  plain "Expected "
+                  actual %|{ number: "not a number" }|
+                  plain " to match "
+                  expected "#<a hash including (number: #<be a kind of Numeric>)>"
+                  plain "."
+                end
+              end,
+            diff:
+              proc do
+                plain_line "  {"
+                expected_line "-   number: #<be a kind of Numeric>"
+                actual_line %|+   number: "not a number"|
+                plain_line "  }"
+              end
+          )
+
+        expect(program).to produce_output_when_run(expected_output).in_color(
+          color_enabled
+        )
+      end
+    end
+
+    it "produces the correct failure message when used in the negative" do
+      as_both_colored_and_uncolored do |color_enabled|
+        snippet = <<~TEST.strip
+          actual = {
+            number: 4
+          }
+          expected = hash_including(
+            number: be_a(Numeric)
+          )
+          expect(actual).not_to match(expected)
+        TEST
+        program = make_plain_test_program(snippet, color_enabled: color_enabled)
+
+        expected_output =
+          build_expected_output(
+            color_enabled: color_enabled,
+            snippet: "expect(actual).not_to match(expected)",
+            expectation:
+              proc do
+                line do
+                  plain "Expected "
+                  actual "{ number: 4 }"
+                  plain " not to match "
+                  expected "#<a hash including (number: #<be a kind of Numeric>)>"
+                  plain "."
+                end
+              end
+          )
+
+        expect(program).to produce_output_when_run(expected_output).in_color(
+          color_enabled
+        )
+      end
+    end
+  end
+
+  context "when the expected value contains a custom matcher defined via RSpec::Matchers::DSL" do
+    it "produces the correct failure message" do
+      as_both_colored_and_uncolored do |color_enabled|
+        snippet = <<~TEST.strip
+          actual = {
+            number: "something else"
+          }
+          expected = hash_including(
+            number: failing_custom_matcher_from_dsl(42)
+          )
+          expect(actual).to match(expected)
+        TEST
+        program = make_plain_test_program(snippet, color_enabled: color_enabled)
+
+        expected_output =
+          build_expected_output(
+            color_enabled: color_enabled,
+            snippet: "expect(actual).to match(expected)",
+            newline_before_expectation: true,
+            expectation:
+              proc do
+                line do
+                  plain "Expected "
+                  actual %|{ number: "something else" }|
+                end
+
+                line do
+                  plain "to match "
+                  expected "#<a hash including (number: #<custom matcher defined via the DSL with value 42>)>"
+                end
+              end,
+            diff:
+              proc do
+                plain_line "  {"
+                expected_line "-   number: #<custom matcher defined via the DSL with value 42>"
+                actual_line %|+   number: "something else"|
+                plain_line "  }"
+              end
+          )
+
+        expect(program).to produce_output_when_run(expected_output).in_color(
+          color_enabled
+        )
+      end
+    end
+  end
+
+  context "when the expected value contains a custom matcher defined from scratch" do
+    it "produces the correct failure message" do
+      as_both_colored_and_uncolored do |color_enabled|
+        snippet = <<~TEST.strip
+          actual = {
+            number: "something else"
+          }
+          expected = hash_including(
+            number: failing_custom_matcher_from_scratch(42)
+          )
+          expect(actual).to match(expected)
+        TEST
+        program = make_plain_test_program(snippet, color_enabled: color_enabled)
+
+        expected_output =
+          build_expected_output(
+            color_enabled: color_enabled,
+            snippet: "expect(actual).to match(expected)",
+            newline_before_expectation: true,
+            expectation:
+              proc do
+                line do
+                  plain "Expected "
+                  actual %|{ number: "something else" }|
+                end
+
+                line do
+                  plain "to match "
+                  expected "#<a hash including (number: #<custom matcher defined from scratch with value 42>)>"
+                end
+              end,
+            diff:
+              proc do
+                plain_line "  {"
+                expected_line "-   number: #<custom matcher defined from scratch with value 42>"
+                actual_line %|+   number: "something else"|
+                plain_line "  }"
+              end
+          )
+
+        expect(program).to produce_output_when_run(expected_output).in_color(
+          color_enabled
+        )
+      end
+    end
+  end
+end

spec/support/integration/matchers.rb

@@ -32,6 +32,40 @@ def pass_with_singleline_failure_message
       PassWithSinglelineFailureMessageMatcher.new
     end
 
+    RSpec::Matchers.define :failing_custom_matcher_from_dsl do |value|
+      match { false }
+
+      description do
+        "custom matcher defined via the DSL with value #{value.inspect}"
+      end
+    end
+
+    def failing_custom_matcher_from_scratch(value)
+      FailingCustomMatcherFromScratch.new(value)
+    end
+
+    class FailingCustomMatcherFromScratch
+      def initialize(value)
+        @value = value
+      end
+
+      def matches?(_)
+        false
+      end
+
+      def description
+        "custom matcher defined from scratch with value #{value.inspect}"
+      end
+
+      def failure_message
+        "Expected custom matcher not to fail, but did"
+      end
+
+      private
+
+      attr_reader :value
+    end
+
     class FailWithIndentedMultilineFailureMessageMatcher
       def matches?(_)
         false