Introduce PredicateMemoization cop and fix offenses

with StrongMemoize

1 files changed, 86 insertions, 0 deletions

diff --git a/spec/rubocop/cop/gitlab/predicate_memoization_spec.rb b/spec/rubocop/cop/gitlab/predicate_memoization_spec.rb
new file mode 100644
index 00000000000..6c731139468
--- /dev/null
+++ b/spec/rubocop/cop/gitlab/predicate_memoization_spec.rb
@@ -0,0 +1,86 @@
+require 'spec_helper'
+require 'rubocop'
+require 'rubocop/rspec/support'
+require_relative '../../../../rubocop/cop/gitlab/predicate_memoization'
+
+describe RuboCop::Cop::Gitlab::PredicateMemoization do
+  include CopHelper
+
+  subject(:cop) { described_class.new }
+
+  shared_examples('registering offense') do |options|
+    let(:offending_lines) { options[:offending_lines] }
+
+    it 'registers an offense when a predicate method is memoizing via ivar' do
+      inspect_source(source)
+
+      aggregate_failures do
+        expect(cop.offenses.size).to eq(offending_lines.size)
+        expect(cop.offenses.map(&:line)).to eq(offending_lines)
+      end
+    end
+  end
+
+  shared_examples('not registering offense') do
+    it 'does not register offenses' do
+      inspect_source(source)
+
+      expect(cop.offenses).to be_empty
+    end
+  end
+
+  context 'when source is a predicate method memoizing via ivar' do
+    it_behaves_like 'registering offense', offending_lines: [3] do
+      let(:source) do
+        <<~RUBY
+          class C
+            def really?
+              @really ||= true
+            end
+          end
+        RUBY
+      end
+    end
+
+    it_behaves_like 'registering offense', offending_lines: [4] do
+      let(:source) do
+        <<~RUBY
+          class C
+            def really?
+              value = true
+              @really ||= value
+            end
+          end
+        RUBY
+      end
+    end
+  end
+
+  context 'when source is a predicate method using ivar with assignment' do
+    it_behaves_like 'not registering offense' do
+      let(:source) do
+        <<~RUBY
+          class C
+            def really?
+              @really = true
+            end
+          end
+        RUBY
+      end
+    end
+  end
+
+  context 'when source is a regular method memoizing via ivar' do
+    it_behaves_like 'not registering offense' do
+      let(:source) do
+        <<~RUBY
+          class C
+            def really
+              @really ||= true
+            end
+          end
+        RUBY
+      end
+    end
+  end
+end