add report_duplicates config option for let_it_be

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## master (unreleased)
 
+- Add support for `report_duplicates` config option for `let_it_be` ([@lHydra][])
+
 - Vernier: Add hooks configuration parameter. ([@lHydra][])
 
 Now you can add more insights to the resulting report by adding event markers from Active Support Notifications.

docs/recipes/let_it_be.md

@@ -266,3 +266,36 @@ end
 And then tag contexts/examples with `:let_it_be_frost` to enable this feature.
 
 Alternatively, you can specify `freeze` modifier explicitly (`let_it_be(freeze: true)`) or configure an alias.
+
+## Report duplicates
+
+Although we suggest using `let_it_be` instead of `let!`, there is one important difference: you can override `let!` definition with the same or nested context, so only the latter one is called; `let_it_be` records could be overridden, but still created. For example:
+
+```ruby
+context "A" do
+  let!(:user) { create(:user, name: "a") }
+  let_it_be(:post) { create(:post, title: "A") }
+
+  specify { expect(User.all.pluck(:name)).to eq ["a"] }
+  specify { expect(Post.all.pluck(:title)).to eq ["A"] }
+
+  context "B" do
+    let!(:user) { create(:user, name: "b") }
+    let_it_be(:post) { create(:post, title: "B") }
+
+    specify { expect(User.all.pluck(:name)).to eq ["b"] }
+    specify { expect(Post.all.pluck(:title)).to eq ["B"] } # fails, because there are two posts
+  end
+end
+```
+
+So for your convenience, you can configure the behavior when let_it_be is overridden.
+
+```ruby
+TestProf::LetItBe.configure do |config|
+  config.report_duplicates = :warn # Rspec.warn_with
+  config.report_duplicates = :raise # Kernel.raise
+end
+```
+
+By default this parameter is disabled. You can configure the behavior that will generate a warning or raise an exception.

lib/test_prof/recipes/rspec/let_it_be.rb

@@ -7,6 +7,8 @@ module TestProf
   # Just like `let`, but persist the result for the whole group.
   # NOTE: Experimental and magical, for more control use `before_all`.
   module LetItBe
+    class DuplicationError < StandardError; end
+
     Modifier = Struct.new(:scope, :block) do
       def call(record, config)
         block.call(record, config)
@@ -32,6 +34,19 @@ def register_modifier(key, on: :let, &block)
         LetItBe.modifiers[key] = Modifier.new(on, block)
       end
 
+      def report_duplicates=(value)
+        value = value.to_sym
+        unless %i[warn raise].include?(value)
+          raise ArgumentError, "#{value} is not acceptable, acceptable values are :warn or :raise"
+        end
+
+        @report_duplicates = value
+      end
+
+      def report_duplicates
+        @report_duplicates ||= false
+      end
+
       def default_modifiers
         @default_modifiers ||= {}
       end
@@ -117,6 +132,8 @@ def let_it_be(identifier, **options, &block)
         instance_variable_get(:"#{PREFIX}#{identifier}")
       end
 
+      report_duplicates(identifier) if LetItBe.config.report_duplicates
+
       LetItBe.module_for(self).module_eval do
         define_method(identifier) do
           # Trying to detect the context
@@ -135,6 +152,18 @@ def let_it_be(identifier, **options, &block)
       let(identifier, &let_accessor)
     end
 
+    private def report_duplicates(identifier)
+      if instance_methods.include?(identifier) && File.basename(__FILE__) == File.basename(instance_method(identifier).source_location[0])
+        error_msg = "let_it_be(:#{identifier}) was redefined in nested group"
+
+        if LetItBe.config.report_duplicates == :warn
+          ::RSpec.warn_with(error_msg)
+        else
+          raise DuplicationError, error_msg
+        end
+      end
+    end
+
     module Freezer
       # Stoplist to prevent freezing objects and theirs associations that are defined
       # with `let_it_be`'s `freeze: false` options during deep freezing.

spec/integrations/fixtures/rspec/let_it_be_nested_fixture.rb

@@ -0,0 +1,180 @@
+# frozen_string_literal: true
+
+require_relative "../../../support/ar_models"
+require_relative "../../../support/transactional_context"
+
+require "test_prof/recipes/rspec/let_it_be"
+
+RSpec.describe "Overriding detection", :transactional do
+  context "when report_duplicates was set as :raise" do
+    context "when let_it_be redefined" do
+      context "when on same nested level" do
+        it "raises a duplication error" do
+          expect do
+            TestProf::LetItBe.configure do |config|
+              config.report_duplicates = :raise
+            end
+
+            RSpec.describe "let_it_be on same nested level" do
+              include TestProf::FactoryBot::Syntax::Methods
+
+              let_it_be(:user) { create(:user) }
+              let_it_be(:user) { create(:user) }
+            end
+          end.to raise_error(TestProf::LetItBe::DuplicationError)
+        end
+      end
+
+      context "when nested level is 2" do
+        it "raises a duplication error" do
+          expect do
+            TestProf::LetItBe.configure do |config|
+              config.report_duplicates = :raise
+            end
+
+            RSpec.describe "let_it_be in nested context" do
+              include TestProf::FactoryBot::Syntax::Methods
+
+              let_it_be(:user) { create(:user) }
+
+              context "nested context level 2" do
+                let_it_be(:user) { create(:user) }
+              end
+            end
+          end.to raise_error(TestProf::LetItBe::DuplicationError)
+        end
+      end
+
+      context "when nested level is 3" do
+        it "raises a duplication error" do
+          expect do
+            TestProf::LetItBe.configure do |config|
+              config.report_duplicates = :raise
+            end
+
+            RSpec.describe "let_it_be in nested context" do
+              include TestProf::FactoryBot::Syntax::Methods
+
+              let_it_be(:user) { create(:user) }
+
+              context "nested context level 2" do
+                context "nested context level 3" do
+                  let_it_be(:user) { create(:user) }
+                end
+              end
+            end
+          end.to raise_error(TestProf::LetItBe::DuplicationError)
+        end
+      end
+    end
+
+    context "when defined let and let_it_be" do
+      it "does not raise a duplication error" do
+        expect do
+          TestProf::LetItBe.configure do |config|
+            config.report_duplicates = :raise
+          end
+
+          RSpec.describe "let_it_be and let" do
+            include TestProf::FactoryBot::Syntax::Methods
+
+            let(:user) { create(:user) }
+
+            context "nested context level 2" do
+              let_it_be(:user) { create(:user) }
+            end
+          end
+        end.not_to raise_error
+      end
+    end
+  end
+
+  context "when report_duplicates was set as :warn" do
+    let(:warning_msg) { "let_it_be(:user) was redefined in nested group" }
+
+    before do
+      allow(::RSpec).to receive(:warn_with).with(warning_msg)
+    end
+
+    context "when let_it_be redefined" do
+      context "when on same nested level" do
+        it "warns a duplication message" do
+          RSpec.describe "let_it_be on same nested level" do
+            include TestProf::FactoryBot::Syntax::Methods
+
+            TestProf::LetItBe.configure do |config|
+              config.report_duplicates = :warn
+            end
+
+            let_it_be(:user) { create(:user) }
+            let_it_be(:user) { create(:user) }
+          end.run
+
+          expect(::RSpec).to have_received(:warn_with).with(warning_msg).once
+        end
+      end
+
+      context "when nested level is 2" do
+        it "warns a duplication message" do
+          RSpec.describe "let_it_be in nested context" do
+            include TestProf::FactoryBot::Syntax::Methods
+
+            TestProf::LetItBe.configure do |config|
+              config.report_duplicates = :warn
+            end
+
+            let_it_be(:user) { create(:user) }
+
+            context "nested context" do
+              let_it_be(:user) { create(:user) }
+            end
+          end.run
+
+          expect(::RSpec).to have_received(:warn_with).with(warning_msg).once
+        end
+      end
+
+      context "when nested level is 3" do
+        it "warns a duplication message" do
+          RSpec.describe "let_it_be in nested context" do
+            include TestProf::FactoryBot::Syntax::Methods
+
+            TestProf::LetItBe.configure do |config|
+              config.report_duplicates = :warn
+            end
+
+            let_it_be(:user) { create(:user) }
+
+            context "nested context level 2" do
+              context "nested context level 3" do
+                let_it_be(:user) { create(:user) }
+              end
+            end
+          end.run
+
+          expect(::RSpec).to have_received(:warn_with).with(warning_msg).once
+        end
+      end
+    end
+
+    context "when defined let and let_it_be" do
+      it "does not warn a duplication message" do
+        RSpec.describe "let_it_be and let" do
+          include TestProf::FactoryBot::Syntax::Methods
+
+          TestProf::LetItBe.configure do |config|
+            config.report_duplicates = :raise
+          end
+
+          let(:user) { create(:user) }
+
+          context "nested context level 2" do
+            let_it_be(:user) { create(:user) }
+          end
+        end.run
+
+        expect(::RSpec).not_to have_received(:warn_with)
+      end
+    end
+  end
+end

spec/integrations/let_it_be_spec.rb

@@ -18,4 +18,10 @@
 
     expect(output).to include("0 failures")
   end
+
+  specify "it detects let_it_be override" do
+    output = run_rspec("let_it_be_nested")
+
+    expect(output).to include("0 failures")
+  end
 end