skip generated branches for method group

Author: daveMueller

Documentation/Changelog.md

@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## Unreleased
 
 ### Fixed
+-Fix .NET 7 Method Group branch coverage issue [#1447](https://github.com/coverlet-coverage/coverlet/issues/1447)
 -Fix ExcludeFromCodeCoverage does not exclude method in a partial class [#1548](https://github.com/coverlet-coverage/coverlet/issues/1548) 
 -Fix ExcludeFromCodeCoverage does not exclude F# task [#1547](https://github.com/coverlet-coverage/coverlet/issues/1547) 
 -Fix issues where ExcludeFromCodeCoverage ignored [#1431](https://github.com/coverlet-coverage/coverlet/issues/1431)

src/coverlet.core/Symbols/CecilSymbolHelper.cs

@@ -6,7 +6,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Runtime.CompilerServices;
-
+using System.Text.RegularExpressions;
 using Coverlet.Core.Abstractions;
 using Coverlet.Core.Extensions;
 
@@ -251,6 +251,46 @@ Lambda cached field pattern
  return false;
  }
 
+ private static bool SkipDelegateCacheField(Instruction instruction)
+ {
+ /*
+ Delegate cached field pattern (e.g. method groups)
+
+ IL_0001: ldc.i4.1
+ IL_0002: newarr [System.Runtime]System.Int32
+ IL_0007: dup
+ IL_0008: ldc.i4.0
+ IL_0009: ldc.i4.1
+ IL_000a: stelem.i4
+ IL_000b: ldsfld class [System.Runtime]System.Func`2<int32, int32> Coverlet.Core.Samples.Tests.Issue_1447/'<>O'::'<0>__Map'
+ IL_0010: dup
+ IL_0011: brtrue.s IL_0026 -> CHECK IF CACHED FIELD IS NULL OR JUMP TO DELEGATE USAGE
+
+ IL_0013: pop
+ IL_0014: ldnull
+ IL_0015: ldftn int32 Coverlet.Core.Samples.Tests.Issue_1447::Map(int32)
+ IL_001b: newobj instance void class [System.Runtime]System.Func`2<int32, int32>::.ctor(object, native int)
+ IL_0020: dup
+ IL_0021: stsfld class [System.Runtime]System.Func`2<int32, int32> Coverlet.Core.Samples.Tests.Issue_1447/'<>O'::'<0>__Map'
+
+ (USE DELEGATE FIELD)
+ IL_0026: call class [System.Runtime]System.Collections.Generic.IEnumerable`1<!!1> [System.Linq]System.Linq.Enumerable::Select<int32, int32>(class [System.Runtime] System.Collections.Generic.IEnumerable`1<!!0>, class [System.Runtime] System.Func`2<!!0, !!1>)
+ */
+
+ Instruction current = instruction.Previous;
+ for (int instructionBefore = 2; instructionBefore > 0 && current.Previous != null; current = current.Previous, instructionBefore--)
+ {
+ if (current.OpCode == OpCodes.Ldsfld && current.Operand is FieldDefinition fd &&
+ // https://github.com/dotnet/roslyn/blob/main/src/Compilers/CSharp/Portable/Symbols/Synthesized/GeneratedNames.cs#L513
+ Regex.IsMatch(fd.Name, "^<\\d+>__") &&
+ IsCompilerGenerated(fd))
+ {
+ return true;
+ }
+ }
+ return false;
+ }
+
  private static bool SkipGeneratedBranchForExceptionRethrown(List<Instruction> instructions, Instruction instruction)
  {
  /* 
@@ -984,7 +1024,7 @@ public IReadOnlyList<BranchPoint> GetBranchPoints(MethodDefinition methodDefinit
  continue;
  }
 
- if (SkipLambdaCachedField(instruction))
+ if (SkipLambdaCachedField(instruction) || SkipDelegateCacheField(instruction))
  {
  continue;
  }

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

@@ -20,9 +20,9 @@ public void Lambda_Issue343()
  {
  CoveragePrepareResult coveragePrepareResult = await TestInstrumentationHelper.Run<Lambda_Issue343>(async instance =>
  {
- instance.InvokeAnonymous_Test();
- await (Task<bool>)instance.InvokeAnonymousAsync_Test();
- }, persistPrepareResultToFile: pathSerialize[0]);
+  instance.InvokeAnonymous_Test();
+  await (Task<bool>)instance.InvokeAnonymousAsync_Test();
+  }, persistPrepareResultToFile: pathSerialize[0]);
  return 0;
  }, new string[] { path });
 
@@ -53,8 +53,8 @@ public void AsyncAwait_Issue_730()
  {
  CoveragePrepareResult coveragePrepareResult = await TestInstrumentationHelper.Run<Issue_730>(async instance =>
  {
- await (Task)instance.Invoke();
- },
+  await (Task)instance.Invoke();
+  },
  persistPrepareResultToFile: pathSerialize[0]);
 
  return 0;
@@ -81,9 +81,9 @@ public void Lambda_Issue760()
  {
  CoveragePrepareResult coveragePrepareResult = await TestInstrumentationHelper.Run<Issue_760>(async instance =>
  {
- await (Task)instance.If();
- await (Task)instance.Foreach();
- },
+  await (Task)instance.If();
+  await (Task)instance.Foreach();
+  },
  persistPrepareResultToFile: pathSerialize[0]);
 
  return 0;
@@ -134,5 +134,35 @@ public void Issue_1056()
  File.Delete(path);
  }
  }
+
+ [Fact]
+ public void Issue_1447()
+ {
+ string path = Path.GetTempFileName();
+ try
+ {
+ FunctionExecutor.Run(async (string[] pathSerialize) =>
+ {
+ CoveragePrepareResult coveragePrepareResult = await TestInstrumentationHelper.Run<Issue_1447>(instance =>
+ {
+ instance.Query1();
+ instance.Query2();
+ return Task.CompletedTask;
+ },
+ persistPrepareResultToFile: pathSerialize[0]);
+
+ return 0;
+ }, new string[] { path });
+
+ TestInstrumentationHelper.GetCoverageResult(path).GenerateReport(show: true)
+ .Document("Instrumentation.Lambda.cs")
+ .AssertLinesCovered((138, 1), (143, 1))
+ .ExpectedTotalNumberOfBranches(0);
+ }
+ finally
+ {
+ File.Delete(path);
+ }
+ }
  }
 }

test/coverlet.core.tests/Samples/Instrumentation.Lambda.cs

@@ -130,4 +130,19 @@ private static object Do2(System.Func<object, object> func)
 
  public void WriteLine(string str) { }
  }
+
+ public class Issue_1447
+ {
+ public System.Collections.Generic.IEnumerable<int> Query1()
+ {
+ return new[] { 1 }.Select(Map);
+ }
+
+ public System.Collections.Generic.IEnumerable<int> Query2()
+ {
+ return new[] { 1 }.Select(Map);
+ }
+
+ private static int Map(int row) => row + 1;
+ }
 }