[Logs Bridge API] Add support for Body set directly on LogRecord for OTLP Exporter.

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+* **Experimental (pre-release builds only):** Added
+  support for `Body` set directly on `LogRecord` via the Logs Bridge API.
+  [#5268](https://github.com/open-telemetry/opentelemetry-dotnet/pull/5268)
+
 * **Experimental (pre-release builds only):** Added
   `LoggerProviderBuilder.AddOtlpExporter` registration extensions.
   [#5103](https://github.com/open-telemetry/opentelemetry-dotnet/pull/5103)

src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/OtlpLogRecordTransformer.cs

@@ -170,6 +170,14 @@ internal OtlpLogs.LogRecord ToOtlpLog(LogRecord logRecord)
                         AddAttribute(otlpLogRecord, result, attributeCountLimit);
                     }
                 }
+
+                // Supports Body set directly on LogRecord for the Logs Bridge API.
+                if (otlpLogRecord.Body == null && logRecord.Body != null)
+                {
+                    // If {OriginalFormat} is not present in the attributes,
+                    // use logRecord.Body if it is set.
+                    otlpLogRecord.Body = new OtlpCommon.AnyValue { StringValue = logRecord.Body };
+                }
             }
 
             if (logRecord.TraceId != default && logRecord.SpanId != default)

test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpLogExporterTests.cs

@@ -589,6 +589,38 @@ public void CheckToOtlpLogRecordBodyIsPopulated(bool includeFormattedMessage)
         Assert.Equal("state", otlpLogRecord.Body.StringValue);
     }
 
+    [Fact]
+    public void LogRecordBodyIsExportedWhenUsingBridgeApi()
+    {
+        var logRecords = new List<LogRecord>();
+
+        using (var loggerProvider = Sdk.CreateLoggerProviderBuilder()
+            .ConfigureServices(services =>
+            {
+                services.AddLogging(builder => builder.AddOpenTelemetry(options =>
+                {
+                    options.AddInMemoryExporter(logRecords);
+                }));
+            })
+            .Build())
+        {
+            var logger = loggerProvider.GetLogger();
+
+            logger.EmitLog(new LogRecordData()
+            {
+                Body = "Hello world",
+            });
+        }
+
+        Assert.Single(logRecords);
+
+        var otlpLogRecordTransformer = new OtlpLogRecordTransformer(DefaultSdkLimitOptions, new());
+
+        var otlpLogRecord = otlpLogRecordTransformer.ToOtlpLog(logRecords[0]);
+
+        Assert.Equal("Hello world", otlpLogRecord.Body?.StringValue);
+    }
+
     [Fact]
     public void CheckToOtlpLogRecordExceptionAttributes()
     {