Condense built-in and DSL RSpec matcher inspection output

lib/super_diff/rspec.rb

@@ -112,7 +112,8 @@ def self.rspec_version
         ObjectInspection::InspectionTreeBuilders::KindOf,
         ObjectInspection::InspectionTreeBuilders::ObjectHavingAttributes,
         # ObjectInspection::InspectionTreeBuilders::Primitive,
-        ObjectInspection::InspectionTreeBuilders::ValueWithin
+        ObjectInspection::InspectionTreeBuilders::ValueWithin,
+        ObjectInspection::InspectionTreeBuilders::RSpecMatcher
       )
     end
   end

lib/super_diff/rspec/object_inspection/inspection_tree_builders.rb

@@ -34,6 +34,10 @@ 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

@@ -0,0 +1,20 @@
+module SuperDiff
+  module RSpec
+    module ObjectInspection
+      module InspectionTreeBuilders
+        class RSpecMatcher < SuperDiff::ObjectInspection::InspectionTreeBuilders::Base
+          def self.applies_to?(value)
+            value.is_a?(::RSpec::Matchers::BuiltIn::BaseMatcher) ||
+              value.is_a?(::RSpec::Matchers::DSL::Matcher)
+          end
+
+          def call
+            SuperDiff::ObjectInspection::InspectionTree.new do
+              add_text { |object| "#<#{object.description}>" }
+            end
+          end
+        end
+      end
+    end
+  end
+end

spec/integration/rspec/unhandled_matcher_spec.rb

@@ -0,0 +1,86 @@
+require "spec_helper"
+
+RSpec.describe "Integration with built-in RSpec matchers", type: :integration do
+  context "when the expected value contains a built-in matcher" do
+    context "that fails" do
+      it "produces the correct failure message when used in the negative" do
+        as_both_colored_and_uncolored do |color_enabled|
+          snippet = <<~TEST.strip
+            expected = hash_including(
+              number: be_a(Numeric)
+            )
+            actual = {
+              number: 4
+            }
+            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
+
+      it "produces the correct failure message when used in the positive" do
+        as_both_colored_and_uncolored do |color_enabled|
+          snippet = <<~TEST.strip
+            expected = hash_including(
+              number: be_a(Numeric)
+            )
+            actual = {
+              number: "not a number"
+            }
+            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
+    end
+  end
+end

spec/unit/rspec/object_inspection/rspec_matcher_spec.rb

@@ -0,0 +1,91 @@
+require "spec_helper"
+
+RSpec.describe SuperDiff, type: :unit do
+  describe ".inspect_object", "for RSpec matchers" do
+    context "given a custom matcher" do
+      let(:custom_matcher) do
+        proc do |expected, &block_arg|
+          declarations =
+            proc do
+              match do |actual|
+                actual.is_a?(Integer) && actual >= 0 &&
+                  (Math.sqrt(actual) % 1).zero?
+              end
+              description { "be a perfect square" }
+            end
+          RSpec::Matchers::DSL::Matcher.new(
+            :be_a_square,
+            declarations,
+            RSpec::Matchers::DSL,
+            *expected,
+            &block_arg
+          )
+        end
+      end
+
+      context "given as_lines: false" do
+        it "returns the matcher's description string" do
+          string =
+            described_class.inspect_object(
+              custom_matcher.call(4),
+              as_lines: false
+            )
+          expect(string).to eq("#<be a perfect square>")
+        end
+      end
+
+      context "given as_lines: true" do
+        it "returns an inspected version of the matcher as multiple lines" do
+          tiered_lines =
+            described_class.inspect_object(
+              custom_matcher.call(4),
+              as_lines: true,
+              type: :delete,
+              indentation_level: 1
+            )
+          expect(tiered_lines).to match(
+            [
+              an_object_having_attributes(
+                type: :delete,
+                indentation_level: 1,
+                value: "#<be a perfect square>"
+              )
+            ]
+          )
+        end
+      end
+    end
+
+    context "given a built-in matcher" do
+      let(:matcher) { be_a(Numeric) }
+
+      context "given as_lines: false" do
+        it "returns the matcher's description string" do
+          string = described_class.inspect_object(matcher, as_lines: false)
+          expect(string).to eq("#<be a kind of Numeric>")
+        end
+      end
+
+      context "given as_lines: true" do
+        it "returns an inspected version of the matcher as multiple lines" do
+          tiered_lines =
+            described_class.inspect_object(
+              matcher,
+              as_lines: true,
+              type: :delete,
+              indentation_level: 1
+            )
+          expect(tiered_lines).to match(
+            [
+              an_object_having_attributes(
+                type: :delete,
+                indentation_level: 1,
+                value: "#<be a kind of Numeric>"
+              )
+            ]
+          )
+        end
+      end
+    end
+  end
+end