Use getPrometheusName for Otel2PrometheusConverter map keys (#6308)

exporters/prometheus/src/main/java/io/opentelemetry/exporter/prometheus/Otel2PrometheusConverter.java

@@ -550,7 +550,7 @@ final class Otel2PrometheusConverter {
 
   private static void putOrMerge(
       Map<String, MetricSnapshot> snapshotsByName, MetricSnapshot snapshot) {
-    String name = snapshot.getMetadata().getName();
+    String name = snapshot.getMetadata().getPrometheusName();
     if (snapshotsByName.containsKey(name)) {
       MetricSnapshot merged = merge(snapshotsByName.get(name), snapshot);
       if (merged != null) {

exporters/prometheus/src/test/java/io/opentelemetry/exporter/prometheus/Otel2PrometheusConverterTest.java

@@ -7,6 +7,7 @@ package io.opentelemetry.exporter.prometheus;
 
 import static io.opentelemetry.api.common.AttributeKey.stringKey;
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatCode;
 
 import io.opentelemetry.api.common.Attributes;
 import io.opentelemetry.sdk.common.InstrumentationScopeInfo;
@@ -108,6 +109,34 @@ class Otel2PrometheusConverterTest {
     assertThat(metricLabels).isEqualTo(expectedMetricLabels);
   }
 
+  @Test
+  void prometheusNameCollisionTest_Issue6277() {
+    // NOTE: Metrics with the same resolved prometheus name should merge. However,
+    // Otel2PrometheusConverter is not responsible for merging individual series, so the merge will
+    // fail if the two different metrics contain overlapping series. Users should deal with this by
+    // adding a view that renames one of the two metrics such that the conflict does not occur.
+    MetricData dotName =
+        createSampleMetricData(
+            "my.metric",
+            "units",
+            MetricDataType.LONG_SUM,
+            Attributes.builder().put("key", "a").build(),
+            Resource.create(Attributes.empty()));
+    MetricData underscoreName =
+        createSampleMetricData(
+            "my_metric",
+            "units",
+            MetricDataType.LONG_SUM,
+            Attributes.builder().put("key", "b").build(),
+            Resource.create(Attributes.empty()));
+
+    List<MetricData> metricData = new ArrayList<>();
+    metricData.add(dotName);
+    metricData.add(underscoreName);
+
+    assertThatCode(() -> converter.convert(metricData)).doesNotThrowAnyException();
+  }
+
   private static Stream<Arguments> resourceAttributesAdditionArgs() {
     List<Arguments> arguments = new ArrayList<>();