Add useful diff representation of Time-like values

This should add a more useful diff for Time instances, as well as make
the diff output from ActiveSupport::TimeWithZone instances readable.

Previously the ActiveSupport::TimeWithZone diff output would contain all
the timezones, leading to several thousand lines in the diff. Now all
time-like instances will work the same way: Single-line diffs will be of
a simple ISO-like string, while the full diff will show which parts of
the time actually differs.

Timezone is promptly shown, both with name and with GMT offset.

Author: Mange

lib/super_diff/differs.rb

@@ -7,10 +7,12 @@ module Differs
     autoload :Empty, "super_diff/differs/empty"
     autoload :Hash, "super_diff/differs/hash"
     autoload :MultilineString, "super_diff/differs/multiline_string"
+    autoload :Time, "super_diff/differs/time"
 
     DEFAULTS = [
       Array,
       Hash,
+      Time,
       MultilineString,
       CustomObject,
       DefaultObject,

lib/super_diff/differs/time.rb

@@ -0,0 +1,24 @@
+module SuperDiff
+  module Differs
+    class Time < Base
+      def self.applies_to?(expected, actual)
+        OperationalSequencers::TimeLike.applies_to?(expected, actual)
+      end
+
+      def call
+        operations.to_diff(indent_level: indent_level)
+      end
+
+      private
+
+      def operations
+        OperationalSequencers::TimeLike.call(
+          expected: expected,
+          actual: actual,
+          extra_operational_sequencer_classes: extra_operational_sequencer_classes,
+          extra_diff_formatter_classes: extra_diff_formatter_classes,
+        )
+      end
+    end
+  end
+end

lib/super_diff/object_inspection/inspectors.rb

@@ -13,6 +13,7 @@ module Inspectors
       autoload :Hash, "super_diff/object_inspection/inspectors/hash"
       autoload :Primitive, "super_diff/object_inspection/inspectors/primitive"
       autoload :String, "super_diff/object_inspection/inspectors/string"
+      autoload :Time, "super_diff/object_inspection/inspectors/time"
     end
   end
 end

lib/super_diff/object_inspection/inspectors/time.rb

@@ -0,0 +1,13 @@
+module SuperDiff
+  module ObjectInspection
+    module Inspectors
+      TIME_FORMAT = "%Y-%m-%d %H:%M:%S.%3N %Z %:z".freeze
+
+      Time = InspectionTree.new do
+        add_text do |time|
+          "#{time.strftime(TIME_FORMAT)} (#{time.class})"
+        end
+      end
+    end
+  end
+end

lib/super_diff/object_inspection/map.rb

@@ -16,6 +16,8 @@ def call(object)
             Inspectors::Hash
           when String
             Inspectors::String
+          when Time
+            Inspectors::Time
           when true, false, nil, Symbol, Numeric, Regexp, Class
             Inspectors::Primitive
           else

lib/super_diff/operational_sequencers.rb

@@ -10,6 +10,7 @@ module OperationalSequencers
       :MultilineString,
       "super_diff/operational_sequencers/multiline_string",
     )
+    autoload :TimeLike, "super_diff/operational_sequencers/time_like"
 
     DEFAULTS = [Array, Hash, CustomObject].freeze
   end

lib/super_diff/operational_sequencers/time_like.rb

@@ -0,0 +1,21 @@
+module SuperDiff
+  module OperationalSequencers
+    class TimeLike < CustomObject
+      def self.applies_to?(expected, actual)
+        (expected.is_a?(Time) && actual.is_a?(Time)) ||
+          (
+            # Check for ActiveSupport's #acts_like_time? for their time-like objects
+            # (like ActiveSupport::TimeWithZone).
+            expected.respond_to?(:acts_like_time?) && expected.acts_like_time? &&
+            actual.respond_to?(:acts_like_time?) && actual.acts_like_time?
+          )
+      end
+
+      protected
+
+      def attribute_names
+        ["year", "month", "day", "hour", "min", "sec", "nsec", "zone", "gmt_offset"]
+      end
+    end
+  end
+end

spec/integration/rspec/eq_matcher_spec.rb

@@ -142,24 +142,158 @@
 
     it "produces the correct failure message when used in the negative" do
       as_both_colored_and_uncolored do |color_enabled|
-        snippet = %|expect("Jennifer").to eq("Marty")|
+        snippet = %|expect("Jennifer").not_to eq("Jennifer")|
         program = make_plain_test_program(
           snippet,
           color_enabled: color_enabled,
         )
 
         expected_output = build_expected_output(
           color_enabled: color_enabled,
-          snippet: %|expect("Jennifer").to eq("Marty")|,
+          snippet: %|expect("Jennifer").not_to eq("Jennifer")|,
           expectation: proc {
             line do
               plain "Expected "
               beta %|"Jennifer"|
+              plain " not to eq "
+              alpha %|"Jennifer"|
+              plain "."
+            end
+          },
+        )
+
+        expect(program).
+          to produce_output_when_run(expected_output).
+          in_color(color_enabled)
+      end
+    end
+  end
+
+  context "when comparing two different Time instances" do
+    it "produces the correct failure message when used in the positive" do
+      as_both_colored_and_uncolored do |color_enabled|
+        snippet = <<~RUBY
+          expected = Time.utc(2011, 12, 13, 14, 15, 16)
+          actual = Time.utc(2011, 12, 13, 14, 15, 16, 500_000)
+          expect(expected).to eq(actual)
+        RUBY
+        program = make_plain_test_program(
+          snippet,
+          color_enabled: color_enabled,
+        )
+
+        expected_output = build_expected_output(
+          color_enabled: color_enabled,
+          snippet: %|expect(expected).to eq(actual)|,
+          expectation: proc {
+            line do
+              plain "Expected "
+              beta %|2011-12-13 14:15:16.000 UTC +00:00 (Time)|
               plain " to eq "
-              alpha %|"Marty"|
+              alpha %|2011-12-13 14:15:16.500 UTC +00:00 (Time)|
               plain "."
             end
           },
+          diff: proc {
+            plain_line "  #<Time {"
+            plain_line "    year: 2011,"
+            plain_line "    month: 12,"
+            plain_line "    day: 13,"
+            plain_line "    hour: 14,"
+            plain_line "    min: 15,"
+            plain_line "    sec: 16,"
+            alpha_line "-   nsec: 500000000,"
+            beta_line  "+   nsec: 0,"
+            plain_line "    zone: \"UTC\","
+            plain_line "    gmt_offset: 0"
+            plain_line "  }>"
+          },
+        )
+
+        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 = <<~RUBY
+          time = Time.utc(2011, 12, 13, 14, 15, 16)
+          expect(time).not_to eq(time)
+        RUBY
+        program = make_plain_test_program(
+          snippet,
+          color_enabled: color_enabled,
+        )
+
+        expected_output = build_expected_output(
+          color_enabled: color_enabled,
+          snippet: %|expect(time).not_to eq(time)|,
+          newline_before_expectation: true,
+          expectation: proc {
+            line do
+              plain " Expected "
+              beta %|2011-12-13 14:15:16.000 UTC +00:00 (Time)|
+            end
+
+            line do
+              plain "not to eq "
+              alpha %|2011-12-13 14:15:16.000 UTC +00:00 (Time)|
+            end
+          },
+        )
+
+        expect(program).
+          to produce_output_when_run(expected_output).
+          in_color(color_enabled)
+      end
+    end
+  end
+
+  context "when comparing two different Time and ActiveSupport::TimeWithZone instances" do
+    it "produces the correct failure message when used in the positive" do
+      as_both_colored_and_uncolored do |color_enabled|
+        snippet = <<~RUBY
+          expected = Time.utc(2011, 12, 13, 14, 15, 16)
+          actual = Time.utc(2011, 12, 13, 15, 15, 16).in_time_zone("Europe/Stockholm")
+          expect(expected).to eq(actual)
+        RUBY
+        program = make_rspec_rails_test_program(
+          snippet,
+          color_enabled: color_enabled,
+        )
+
+        expected_output = build_expected_output(
+          color_enabled: color_enabled,
+          snippet: %|expect(expected).to eq(actual)|,
+          expectation: proc {
+            line do
+              plain "Expected "
+              beta %|2011-12-13 14:15:16.000 UTC +00:00 (Time)|
+            end
+
+            line do
+              plain "   to eq "
+              alpha %|2011-12-13 16:15:16.000 CET +01:00 (ActiveSupport::TimeWithZone)|
+            end
+          },
+          diff: proc {
+            plain_line "  #<ActiveSupport::TimeWithZone {"
+            plain_line "    year: 2011,"
+            plain_line "    month: 12,"
+            plain_line "    day: 13,"
+            alpha_line "-   hour: 16,"
+            beta_line  "+   hour: 14,"
+            plain_line "    min: 15,"
+            plain_line "    sec: 16,"
+            plain_line "    nsec: 0,"
+            alpha_line "-   zone: \"CET\","
+            beta_line  "+   zone: \"UTC\","
+            alpha_line "-   gmt_offset: 3600"
+            beta_line  "+   gmt_offset: 0"
+            plain_line "  }>"
+          },
         )
 
         expect(program).