Address Copilot review feedback: use exposed target_info name for collision check

Author: dashpole

exporters/prometheus/src/exporter_utils.cc

@@ -141,7 +141,10 @@ std::vector<prometheus_client::MetricFamily> PrometheusExporterUtils::TranslateT
   std::unordered_map<std::string, std::size_t> family_index_by_name;
   for (std::size_t i = 0; i < output.size(); ++i)
   {
-    family_index_by_name.emplace(output[i].name, i);
+    std::string exposed_name = output[i].type == prometheus_client::MetricType::Info
+                                   ? output[i].name + "_info"
+                                   : output[i].name;
+    family_index_by_name.emplace(std::move(exposed_name), i);
   }
 
   for (const auto &instrumentation_info : data.scope_metric_data_)

exporters/prometheus/test/exporter_utils_test.cc

@@ -617,4 +617,56 @@ TEST(PrometheusExporterUtils, MultipleScopesMetricFamilyCollisions)
   EXPECT_DOUBLE_EQ(translated[0].metric[1].counter.value, 20.0);
 }
 
+TEST(PrometheusExporterUtils, TargetInfoMetricFamilyCollisions)
+{
+  Resource resource = Resource::Create(ResourceAttributes{{"service.name", "test_service"}});
+  auto scope        = InstrumentationScope::Create("scope_1", "1.0.0");
+
+  metric_sdk::LastValuePointData target_gauge_point{};
+  target_gauge_point.value_              = 42.0;
+  target_gauge_point.is_lastvalue_valid_ = true;
+
+  metric_sdk::LastValuePointData target_info_gauge_point{};
+  target_info_gauge_point.value_              = 99.0;
+  target_info_gauge_point.is_lastvalue_valid_ = true;
+
+  // A unitless gauge named "target" does not collide with the generated Info family
+  // (which is exposed as "target_info" in Prometheus text format).
+  metric_sdk::MetricData target_gauge{
+      metric_sdk::InstrumentDescriptor{"target", "target gauge description", "",
+                                       metric_sdk::InstrumentType::kObservableGauge,
+                                       metric_sdk::InstrumentValueType::kDouble},
+      metric_sdk::AggregationTemporality::kCumulative, opentelemetry::common::SystemTimestamp{},
+      opentelemetry::common::SystemTimestamp{},
+      std::vector<metric_sdk::PointDataAttributes>{{{}, target_gauge_point}}};
+
+  // A gauge named "target_info" collides with the generated Info family exposed as
+  // "target_info" and is dropped due to type conflict.
+  metric_sdk::MetricData target_info_gauge{
+      metric_sdk::InstrumentDescriptor{"target_info", "conflicting target_info gauge", "",
+                                       metric_sdk::InstrumentType::kObservableGauge,
+                                       metric_sdk::InstrumentValueType::kDouble},
+      metric_sdk::AggregationTemporality::kCumulative, opentelemetry::common::SystemTimestamp{},
+      opentelemetry::common::SystemTimestamp{},
+      std::vector<metric_sdk::PointDataAttributes>{{{}, target_info_gauge_point}}};
+
+  metric_sdk::ResourceMetrics data{
+      &resource,
+      std::vector<metric_sdk::ScopeMetrics>{
+          {scope.get(), std::vector<metric_sdk::MetricData>{target_gauge, target_info_gauge}}}};
+
+  auto translated = PrometheusExporterUtils::TranslateToPrometheus(
+      data, /*populate_target_info=*/true, /*without_otel_scope=*/false,
+      /*without_units=*/false, /*without_type_suffix=*/false);
+
+  ASSERT_EQ(translated.size(), 2U);
+  EXPECT_EQ(translated[0].name, "target");
+  EXPECT_EQ(translated[0].type, prometheus_client::MetricType::Info);
+  EXPECT_EQ(translated[1].name, "target");
+  EXPECT_EQ(translated[1].help, "target gauge description");
+  EXPECT_EQ(translated[1].type, prometheus_client::MetricType::Gauge);
+  ASSERT_EQ(translated[1].metric.size(), 1U);
+  EXPECT_DOUBLE_EQ(translated[1].metric[0].gauge.value, 42.0);
+}
+
 OPENTELEMETRY_END_NAMESPACE