[OpenTelemetry.Instrumentation.AWSLambda] Do not crash on empty LambdaContext

src/OpenTelemetry.Instrumentation.AWSLambda/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+* Trace instrumentation will not fail with an exception
+  if empty `LambdaContext` instance is passed.
+  ([#2457](https://github.com/open-telemetry/opentelemetry-dotnet-contrib/pull/2457))
+
 ## 1.10.0-rc.1
 
 Released 2025-Jan-06

src/OpenTelemetry.Instrumentation.AWSLambda/Implementation/AWSLambdaUtils.cs

@@ -170,14 +170,19 @@ internal IEnumerable<KeyValuePair<string, object>> GetFunctionTags<TInput>(TInpu
         return items.Length >= 5 ? items[4] : null;
     }
 
-    private static string GetFaasId(string functionArn)
+    private static string? GetFaasId(string? functionArn)
     {
+        if (string.IsNullOrEmpty(functionArn))
+        {
+            return null;
+        }
+
         var faasId = functionArn;
 
         // According to faas.id description https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/instrumentation/aws-lambda.md#all-triggers
         // the 8th part of arn (function version or alias, see https://docs.aws.amazon.com/lambda/latest/dg/lambda-api-permissions-ref.html)
         // should not be included into faas.id
-        var items = functionArn.Split(':');
+        var items = functionArn!.Split(':');
         if (items.Length >= 8)
         {
             faasId = string.Join(":", items.Take(7));

test/OpenTelemetry.Instrumentation.AWSLambda.Tests/AWSLambdaWrapperTests.cs

@@ -264,6 +264,35 @@ public void OnFunctionStart_ColdStart_ColdStartTagHasCorrectValue(int invocation
         Assert.Contains(activity.TagObjects, x => x.Key == ExpectedSemanticConventions.AttributeFaasColdStart && expectedColdStartValue.Equals(x.Value));
     }
 
+    [Fact]
+    public async Task TraceAsyncDoesNotCrashForEmptyLambdaContext()
+    {
+        var emptyLambdaContext = new SampleLambdaContext
+        {
+            AwsRequestId = null!,
+            ClientContext = null,
+            FunctionName = null!,
+            FunctionVersion = null!,
+            Identity = null!,
+            InvokedFunctionArn = null!,
+            Logger = null!,
+            LogGroupName = null!,
+            LogStreamName = null!,
+            MemoryLimitInMB = 0,
+            RemainingTime = TimeSpan.Zero,
+        };
+
+        using var tracerProvider = Sdk.CreateTracerProviderBuilder()
+                   .AddAWSLambdaConfigurations(opt =>
+                   {
+                       opt.SemanticConventionVersion = SemanticConventionVersion.Latest;
+                   })
+                   .Build();
+
+        // We simply verify that no exception is thrown here.
+        await AWSLambdaWrapper.TraceAsync(tracerProvider, this.sampleHandlers.SampleHandlerAsyncInputAndNoReturn, "TestStream", emptyLambdaContext);
+    }
+
     private static ActivityContext CreateParentContext()
     {
         var traceId = ActivityTraceId.CreateFromString(TraceId.AsSpan());

test/OpenTelemetry.Instrumentation.AWSLambda.Tests/SampleLambdaContext.cs

@@ -7,25 +7,25 @@ namespace OpenTelemetry.Instrumentation.AWSLambda.Tests;
 
 internal class SampleLambdaContext : ILambdaContext
 {
-    public string AwsRequestId { get; } = "testrequestid";
+    public string AwsRequestId { get; set; } = "testrequestid";
 
-    public IClientContext? ClientContext { get; }
+    public IClientContext? ClientContext { get; set; }
 
-    public string FunctionName { get; } = "testfunction";
+    public string FunctionName { get; set; } = "testfunction";
 
-    public string FunctionVersion { get; } = "latest";
+    public string FunctionVersion { get; set; } = "latest";
 
-    public ICognitoIdentity? Identity { get; }
+    public ICognitoIdentity? Identity { get; set; }
 
-    public string InvokedFunctionArn { get; } = "arn:aws:lambda:us-east-1:111111111111:function:testfunction";
+    public string InvokedFunctionArn { get; set; } = "arn:aws:lambda:us-east-1:111111111111:function:testfunction";
 
-    public ILambdaLogger? Logger { get; }
+    public ILambdaLogger? Logger { get; set; }
 
-    public string? LogGroupName { get; }
+    public string? LogGroupName { get; set; }
 
-    public string? LogStreamName { get; }
+    public string? LogStreamName { get; set; }
 
-    public int MemoryLimitInMB { get; }
+    public int MemoryLimitInMB { get; set; }
 
-    public TimeSpan RemainingTime { get; }
+    public TimeSpan RemainingTime { get; set; }
 }