ExcludeFromCodeCoverage attribute on local functions ignores lambda expression

Documentation/Changelog.md

@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 -Await foreach has wrong branch coverage when method is generic [#1210](https://github.com/coverlet-coverage/coverlet/issues/1210)
+-ExcludeFromCodeCoverage attribute on local functions ignores lambda expression [#1302](https://github.com/coverlet-coverage/coverlet/issues/1302)
 
 ## Release date 2022-02-06
 ### Packages  

src/coverlet.core/Instrumentation/Instrumenter.cs

@@ -45,6 +45,7 @@ internal class Instrumenter
         private List<string> _excludedSourceFiles;
         private List<string> _branchesInCompiledGeneratedClass;
         private List<(MethodDefinition, int)> _excludedMethods;
+        private List<string> _excludedLambdaMethods;
         private List<string> _excludedCompilerGeneratedTypes;
         private readonly string[] _doesNotReturnAttributes;
         private ReachabilityHelper _reachabilityHelper;
@@ -500,12 +501,18 @@ private void InstrumentType(TypeDefinition type)
                     continue;
                 }
 
+                if (_excludedLambdaMethods != null && _excludedLambdaMethods.Contains(method.FullName))
+                {
+                    continue;
+                }
+
                 if (!customAttributes.Any(IsExcludeAttribute))
                 {
                     InstrumentMethod(method);
                 }
                 else
                 {
+                    (_excludedLambdaMethods ??= new List<string>()).AddRange(CollectLambdaMethodsInsideLocalFunction(method));
                     (_excludedMethods ??= new List<(MethodDefinition, int)>()).Add((method, ordinal));
                 }
             }
@@ -842,6 +849,19 @@ internal bool IsSynthesizedNameOf(string name, string methodName, int methodOrdi
                 (name.IndexOf($"<{methodName}>g__") != -1 && name.IndexOf($"|{methodOrdinal}_") != -1);
         }
 
+        private static IEnumerable<string> CollectLambdaMethodsInsideLocalFunction(MethodDefinition methodDefinition)
+        {
+            if (!methodDefinition.Name.Contains(">g__")) yield break;
+
+            foreach (Instruction instruction in methodDefinition.Body.Instructions.ToList())
+            {
+                if (instruction.OpCode == OpCodes.Ldftn && instruction.Operand is MethodReference mr && mr.Name.Contains(">b__"))
+                {
+                    yield return mr.FullName;
+                }
+            }
+        }
+
         /// <summary>
         /// A custom importer created specifically to allow the instrumentation of System.Private.CoreLib by
         /// removing the external references to netstandard that are generated when instrumenting a typical

test/coverlet.core.tests/Coverage/CoverageTests.ExcludeFromCoverageAttribute.cs

@@ -277,5 +277,32 @@ public void ExcludeFromCodeCoverageAutoGeneratedGet()
                 File.Delete(path);
             }
         }
+
+        [Fact]
+        public void ExcludeFromCodeCoverage_Issue1302()
+        {
+            string path = Path.GetTempFileName();
+            try
+            {
+                FunctionExecutor.Run(async (string[] pathSerialize) =>
+                {
+                    CoveragePrepareResult coveragePrepareResult = await TestInstrumentationHelper.Run<Issue1302>(instance =>
+                    {
+                        instance.Run();
+                        return Task.CompletedTask;
+                    }, persistPrepareResultToFile: pathSerialize[0]);
+
+                    return 0;
+                }, new string[] { path });
+
+                TestInstrumentationHelper.GetCoverageResult(path)
+                    .Document("Instrumentation.ExcludeFromCoverage.Issue1302.cs")
+                    .AssertNonInstrumentedLines(BuildConfiguration.Debug, 10, 13);
+            }
+            finally
+            {
+                File.Delete(path);
+            }
+        }
     }
 }

test/coverlet.core.tests/Samples/Instrumentation.ExcludeFromCoverage.Issue1302.cs

@@ -0,0 +1,18 @@
+using System;
+
+namespace Coverlet.Core.Samples.Tests
+{
+    public class Issue1302
+    {
+        public void Run()
+        {
+            [System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
+            static Func<string, bool> LocalFunction()
+            {
+                return myString => myString.Length == 10;
+            }
+
+            LocalFunction();
+        }
+    }
+}