Use Module#prepend for method instrumentationfix-method-instrumentation

By using Module#prepend we can define a Module containing all proxy
methods. This removes the need for setting up crazy method alias chains
and in turn prevents us from having to deal with all that madness (e.g.
methods calling each other recursively).

Fixes gitlab-org/gitlab-ce#15281

1 files changed, 37 insertions, 14 deletions

diff --git a/spec/lib/gitlab/metrics/instrumentation_spec.rb b/spec/lib/gitlab/metrics/instrumentation_spec.rb
index ad4290c43bb..5c885a7a982 100644
--- a/spec/lib/gitlab/metrics/instrumentation_spec.rb
+++ b/spec/lib/gitlab/metrics/instrumentation_spec.rb
@@ -33,8 +33,16 @@ describe Gitlab::Metrics::Instrumentation do
         described_class.instrument_method(@dummy, :foo)
       end
 
-      it 'renames the original method' do
-        expect(@dummy).to respond_to(:_original_foo)
+      it 'instruments the Class' do
+        target = @dummy.singleton_class
+
+        expect(described_class.instrumented?(target)).to eq(true)
+      end
+
+      it 'defines a proxy method' do
+        mod = described_class.proxy_module(@dummy.singleton_class)
+
+        expect(mod.method_defined?(:foo)).to eq(true)
       end
 
       it 'calls the instrumented method with the correct arguments' do
@@ -76,6 +84,14 @@ describe Gitlab::Metrics::Instrumentation do
 
         expect(dummy.method(:test).arity).to eq(0)
       end
+
+      describe 'when a module is instrumented multiple times' do
+        it 'calls the instrumented method with the correct arguments' do
+          described_class.instrument_method(@dummy, :foo)
+
+          expect(@dummy.foo).to eq('foo')
+        end
+      end
     end
 
     describe 'with metrics disabled' do
@@ -86,7 +102,9 @@ describe Gitlab::Metrics::Instrumentation do
       it 'does not instrument the method' do
         described_class.instrument_method(@dummy, :foo)
 
-        expect(@dummy).to_not respond_to(:_original_foo)
+        target = @dummy.singleton_class
+
+        expect(described_class.instrumented?(target)).to eq(false)
       end
     end
   end
@@ -100,8 +118,14 @@ describe Gitlab::Metrics::Instrumentation do
           instrument_instance_method(@dummy, :bar)
       end
 
-      it 'renames the original method' do
-        expect(@dummy.method_defined?(:_original_bar)).to eq(true)
+      it 'instruments instances of the Class' do
+        expect(described_class.instrumented?(@dummy)).to eq(true)
+      end
+
+      it 'defines a proxy method' do
+        mod = described_class.proxy_module(@dummy)
+
+        expect(mod.method_defined?(:bar)).to eq(true)
       end
 
       it 'calls the instrumented method with the correct arguments' do
@@ -144,7 +168,7 @@ describe Gitlab::Metrics::Instrumentation do
         described_class.
           instrument_instance_method(@dummy, :bar)
 
-        expect(@dummy.method_defined?(:_original_bar)).to eq(false)
+        expect(described_class.instrumented?(@dummy)).to eq(false)
       end
     end
   end
@@ -167,18 +191,17 @@ describe Gitlab::Metrics::Instrumentation do
     it 'recursively instruments a class hierarchy' do
       described_class.instrument_class_hierarchy(@dummy)
 
-      expect(@child1).to respond_to(:_original_child1_foo)
-      expect(@child2).to respond_to(:_original_child2_foo)
+      expect(described_class.instrumented?(@child1.singleton_class)).to eq(true)
+      expect(described_class.instrumented?(@child2.singleton_class)).to eq(true)
 
-      expect(@child1.method_defined?(:_original_child1_bar)).to eq(true)
-      expect(@child2.method_defined?(:_original_child2_bar)).to eq(true)
+      expect(described_class.instrumented?(@child1)).to eq(true)
+      expect(described_class.instrumented?(@child2)).to eq(true)
     end
 
     it 'does not instrument the root module' do
       described_class.instrument_class_hierarchy(@dummy)
 
-      expect(@dummy).to_not respond_to(:_original_foo)
-      expect(@dummy.method_defined?(:_original_bar)).to eq(false)
+      expect(described_class.instrumented?(@dummy)).to eq(false)
     end
   end
 
@@ -190,7 +213,7 @@ describe Gitlab::Metrics::Instrumentation do
     it 'instruments all public class methods' do
       described_class.instrument_methods(@dummy)
 
-      expect(@dummy).to respond_to(:_original_foo)
+      expect(described_class.instrumented?(@dummy.singleton_class)).to eq(true)
     end
 
     it 'only instruments methods directly defined in the module' do
@@ -223,7 +246,7 @@ describe Gitlab::Metrics::Instrumentation do
     it 'instruments all public instance methods' do
       described_class.instrument_instance_methods(@dummy)
 
-      expect(@dummy.method_defined?(:_original_bar)).to eq(true)
+      expect(described_class.instrumented?(@dummy)).to eq(true)
     end
 
     it 'only instruments methods directly defined in the module' do