feat(core)!: remove nonstandard append mode

core/include/prometheus/registry.h

@@ -50,10 +50,6 @@ class PROMETHEUS_CPP_CORE_EXPORT Registry : public Collectable {
     Merge,
     /// \brief Throws if a family with the same name already exists.
     Throw,
-    /// \brief Never merge and always create a new family. This violates the
-    /// prometheus specification but was the default behavior in earlier
-    /// versions
-    NonStandardAppend,
   };
 
   /// \brief name Create a new registry.

core/src/registry.cc

@@ -120,15 +120,13 @@ Family<T>& Registry::Add(const std::string& name, const std::string& help,
     }
   }
 
-  if (insert_behavior_ != InsertBehavior::NonStandardAppend) {
-    auto same_name = [&name](const std::unique_ptr<Family<T>>& family) {
-      return name == family->GetName();
-    };
+  auto same_name = [&name](const std::unique_ptr<Family<T>>& family) {
+    return name == family->GetName();
+  };
 
-    auto it = std::find_if(families.begin(), families.end(), same_name);
-    if (it != families.end()) {
-      throw std::invalid_argument("Family name already exists");
-    }
+  auto it = std::find_if(families.begin(), families.end(), same_name);
+  if (it != families.end()) {
+    throw std::invalid_argument("Family name already exists");
   }
 
   auto family = detail::make_unique<Family<T>>(name, help, labels);

core/tests/registry_test.cc

@@ -81,23 +81,6 @@ TEST(RegistryTest, reject_different_type_than_summary) {
   EXPECT_ANY_THROW(BuildHistogram().Name(same_name).Register(registry));
 }
 
-TEST(RegistryTest, append_same_families) {
-  Registry registry{Registry::InsertBehavior::NonStandardAppend};
-
-  std::size_t loops = 4;
-
-  while (loops-- > 0) {
-    BuildCounter()
-        .Name("counter")
-        .Help("Test Counter")
-        .Register(registry)
-        .Add({{"name", "test_counter"}});
-  }
-
-  auto collected = registry.Collect();
-  EXPECT_EQ(4U, collected.size());
-}
-
 TEST(RegistryTest, throw_for_same_family_name) {
   const auto same_name = std::string{"same_name"};
   Registry registry{Registry::InsertBehavior::Throw};