Add custom inspection for ActionDispatch::Request (#294)

Fixes #160.

Per investigation detailed on that issue, the default object inspection tree builder
recursively works through all `ActionDispatch::Request` instance
variables. This includes `env`, which can have enormous values,
including and especially the app's entire route set.

Since the Rails code itself customizes inspection for this class, we'll do the same here.

Author: jas14

lib/super_diff/action_dispatch.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+require 'super_diff/action_dispatch/inspection_tree_builders'
+
+module SuperDiff
+  module ActionDispatch
+    SuperDiff.configure do |config|
+      config.prepend_extra_inspection_tree_builder_classes(
+        InspectionTreeBuilders::Request
+      )
+    end
+  end
+end

lib/super_diff/action_dispatch/inspection_tree_builders.rb

@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+module SuperDiff
+  module ActionDispatch
+    module InspectionTreeBuilders
+      autoload(
+        :Request,
+        'super_diff/action_dispatch/inspection_tree_builders/request'
+      )
+    end
+  end
+end

lib/super_diff/action_dispatch/inspection_tree_builders/request.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+module SuperDiff
+  module ActionDispatch
+    module InspectionTreeBuilders
+      class Request < Core::AbstractInspectionTreeBuilder
+        def self.applies_to?(value)
+          value.is_a?(::ActionDispatch::Request)
+        end
+
+        def call
+          Core::InspectionTree.new do |t1|
+            t1.as_lines_when_rendering_to_lines do |t2|
+              t2.add_text object.inspect
+            end
+          end
+        end
+      end
+    end
+  end
+end

lib/super_diff/rails.rb

@@ -2,3 +2,4 @@
 
 require 'super_diff/active_support'
 require 'super_diff/active_record' if defined?(ActiveRecord)
+require 'super_diff/action_dispatch' if defined?(ActionDispatch)

spec/integration/rails/action_dispatch_spec.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe 'Integration with ActionDispatch', type: :integration, action_dispatch: true do
+  context "when using 'super_diff/rspec-rails'" do
+    include_context 'integration with ActionDispatch'
+
+    def make_program(test, color_enabled:)
+      make_rspec_rails_test_program(test, color_enabled: color_enabled)
+    end
+  end
+
+  context "when using 'super_diff/action_dispatch'" do
+    include_context 'integration with ActionDispatch'
+
+    def make_program(test, color_enabled:)
+      make_rspec_action_dispatch_program(test, color_enabled: color_enabled)
+    end
+  end
+end

spec/spec_helper.rb

@@ -25,6 +25,12 @@
   active_record_available = false
 end
 
+begin
+  require 'action_dispatch'
+rescue LoadError
+  # ActionDispatch isn't available (presumably because we're not testing it)
+end
+
 Dir
   .glob(File.expand_path('support/**/*.rb', __dir__))
   .reject { |file| file.include?('/models/active_record/') && !active_record_available }
@@ -52,6 +58,7 @@
   config.default_formatter = 'documentation' unless %w[true 1].include?(ENV.fetch('CI', nil))
 
   config.filter_run_excluding active_record: true unless active_record_available
+  config.filter_run_excluding action_dispatch: true unless defined?(ActionDispatch)
   config.filter_run_excluding active_support: true unless defined?(ActiveSupport)
   config.filter_run_excluding with_superdiff_rspec: false
 

spec/support/integration/helpers.rb

@@ -30,6 +30,10 @@ def make_rspec_active_support_program(test, color_enabled:)
       TestPrograms::RSpecActiveSupport.new(test, color_enabled: color_enabled)
     end
 
+    def make_rspec_action_dispatch_program(test, color_enabled:)
+      TestPrograms::RSpecActionDispatch.new(test, color_enabled: color_enabled)
+    end
+
     def make_rspec_rails_test_program(test, color_enabled:)
       TestPrograms::RSpecRails.new(test, color_enabled: color_enabled)
     end

spec/support/integration/test_programs/rspec_action_dispatch.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+module SuperDiff
+  module IntegrationTests
+    module TestPrograms
+      class RSpecActionDispatch < Base
+        protected
+
+        def test_plan_prelude
+          <<~PRELUDE.strip
+            test_plan.boot
+            test_plan.boot_action_dispatch
+          PRELUDE
+        end
+
+        def test_plan_command
+          'run_rspec_action_dispatch_test'
+        end
+      end
+    end
+  end
+end

spec/support/shared_examples/action_dispatch.rb

@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+shared_examples_for 'integration with ActionDispatch' do
+  context 'when testing attributes of an ActionDispatch::TestResponse' do
+    it 'produces the correct failure message when used in the positive' do
+      as_both_colored_and_uncolored do |color_enabled|
+        snippet = <<~RUBY
+          request = ActionDispatch::TestRequest.create
+          response = ActionDispatch::TestResponse.new(200, {}, []).tap do |response|
+            response.request = request
+          end
+
+          # The other attributes of TestResponse differ across Rails versions. We don't care about them
+          # for the purposes of this test.
+          ActionDispatch::TestResponse.define_method(:attributes_for_super_diff) { {request: request} }
+
+          expect(response).to be_bad_request
+        RUBY
+        program =
+          make_rspec_action_dispatch_program(snippet, color_enabled: color_enabled)
+
+        expected_output =
+          build_expected_output(
+            color_enabled: color_enabled,
+            snippet: 'expect(response).to be_bad_request',
+            newline_before_expectation: true,
+            expectation:
+              proc do
+                line do
+                  plain '                     Expected '
+                  actual '#<ActionDispatch::TestResponse request: #<ActionDispatch::TestRequest GET "http://test.host/" for 0.0.0.0>>'
+                end
+
+                line do
+                  plain 'to return a truthy result for '
+                  expected 'bad_request?'
+                  plain ' or '
+                  expected 'bad_requests?'
+                end
+              end
+          )
+
+        expect(program).to produce_output_when_run(expected_output).in_color(
+          color_enabled
+        )
+      end
+    end
+  end
+end

spec/unit/action_dispatch/object_inspection_spec.rb

@@ -0,0 +1,58 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe SuperDiff, type: :unit do
+  describe '.inspect_object', 'for ActionDispatch objects', action_dispatch: true do
+    context 'given an ActionDispatch::Request' do
+      context 'given as_lines: false' do
+        it 'returns an inspected version of the object' do
+          string =
+            described_class.inspect_object(
+              ActionDispatch::Request.new(
+                {
+                  'REQUEST_METHOD' => 'PUT',
+                  'REMOTE_ADDR' => '10.0.0.1',
+                  Rack::RACK_URL_SCHEME => 'http',
+                  'HTTP_HOST' => 'host.local'
+                }
+              ),
+              as_lines: false
+            )
+          expect(string).to eq(
+            %(#<ActionDispatch::Request PUT "http://host.local" for 10.0.0.1>)
+          )
+        end
+      end
+
+      context 'given as_lines: true' do
+        it 'returns an inspected version of the object on one line' do
+          tiered_lines =
+            described_class.inspect_object(
+              ActionDispatch::Request.new(
+                {
+                  'REQUEST_METHOD' => 'PUT',
+                  'REMOTE_ADDR' => '10.0.0.1',
+                  Rack::RACK_URL_SCHEME => 'http',
+                  'HTTP_HOST' => 'host.local'
+                }
+              ),
+              as_lines: true,
+              type: :noop,
+              indentation_level: 1
+            )
+
+          expect(tiered_lines).to match(
+            [
+              an_object_having_attributes(
+                type: :noop,
+                indentation_level: 1,
+                value: '#<ActionDispatch::Request PUT "http://host.local" for 10.0.0.1>'
+              )
+            ]
+          )
+        end
+      end
+    end
+  end
+end