Incorrect coverage for methods returning IAsyncEnumerable in generic …

…classes (#1430)
coverlet-coverage · Jan 19, 2023 · 04b82c2 · 04b82c2
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diff --git a/Documentation/Changelog.md b/Documentation/Changelog.md
@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## Unreleased
 
 ### Fixed
+-Incorrect coverage for methods returning IAsyncEnumerable in generic classes [#1383](https://github.com/coverlet-coverage/coverlet/issues/1383)
 -Allign published nuget package version to github release version [#1413](https://github.com/coverlet-coverage/coverlet/issues/1413)  
 -Sync nuget and github release versions [#1122](https://github.com/coverlet-coverage/coverlet/issues/1122)  
 

diff --git a/src/coverlet.core/Symbols/CecilSymbolHelper.cs b/src/coverlet.core/Symbols/CecilSymbolHelper.cs
@@ -877,8 +877,10 @@ static bool DisposeCheck(List<Instruction> instructions, Instruction instruction
 
                 if (currentIndex >= 2 &&
                     instructions[currentIndex - 1].OpCode == OpCodes.Ldfld &&
-                    instructions[currentIndex - 1].Operand is FieldDefinition field &&
-                    IsCompilerGenerated(field) && field.FullName.EndsWith("__disposeMode") &&
+                    (
+                        (instructions[currentIndex - 1].Operand is FieldDefinition field && IsCompilerGenerated(field) && field.FullName.EndsWith("__disposeMode")) ||
+                        (instructions[currentIndex - 1].Operand is FieldReference fieldRef && IsCompilerGenerated(fieldRef.Resolve()) && fieldRef.FullName.EndsWith("__disposeMode"))
+                    ) &&
                     (instructions[currentIndex - 2].OpCode == OpCodes.Ldarg ||
                      instructions[currentIndex - 2].OpCode == OpCodes.Ldarg_0))
                 {

diff --git a/test/coverlet.core.tests/Coverage/CoverageTests.GenericAsyncIterator.cs b/test/coverlet.core.tests/Coverage/CoverageTests.GenericAsyncIterator.cs
@@ -0,0 +1,42 @@
+// Copyright (c) Toni Solarin-Sodara
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System.Collections.Generic;
+using System.IO;
+using System.Threading.Tasks;
+using Coverlet.Core.Samples.Tests;
+using Xunit;
+
+namespace Coverlet.Core.Tests
+{
+    public partial class CoverageTests
+    {
+        [Fact]
+        public void GenericAsyncIterator()
+        {
+            string path = Path.GetTempFileName();
+            try
+            {
+                FunctionExecutor.Run(async (string[] pathSerialize) =>
+                {
+                    CoveragePrepareResult coveragePrepareResult = await TestInstrumentationHelper.Run<GenericAsyncIterator<int>>(instance =>
+                    {
+                        List<int> res = ((Task<List<int>>)instance.Issue1383()).GetAwaiter().GetResult();
+
+                        return Task.CompletedTask;
+                    }, persistPrepareResultToFile: pathSerialize[0]);
+                    return 0;
+                }, new string[] { path });
+
+                TestInstrumentationHelper.GetCoverageResult(path)
+                    .Document("Instrumentation.GenericAsyncIterator.cs")
+                    .AssertLinesCovered(BuildConfiguration.Debug, (13, 1), (14, 1), (20, 1), (21, 1), (22, 1))
+                    .ExpectedTotalNumberOfBranches(BuildConfiguration.Debug, 0);
+            }
+            finally
+            {
+                File.Delete(path);
+            }
+        }
+    }
+}
diff --git a/test/coverlet.core.tests/Coverage/InstrumenterHelper.cs b/test/coverlet.core.tests/Coverage/InstrumenterHelper.cs
@@ -101,7 +101,7 @@ public static async Task<CoveragePrepareResult> Run<T>(Func<dynamic, Task> callM
                 IncludeFilters = (includeFilter is null ? defaultFilters(fileName) : includeFilter(fileName)).Concat(
                 new string[]
                 {
-                    $"[{Path.GetFileNameWithoutExtension(fileName)}*]{typeof(T).FullName}*"
+                    $"[{Path.GetFileNameWithoutExtension(fileName)}*]{GetTypeFullName<T>()}*"
                 }).ToArray(),
                 IncludeDirectories = Array.Empty<string>(),
                 ExcludeFilters = (excludeFilter is null ? defaultFilters(fileName) : excludeFilter(fileName)).Concat(new string[]
@@ -180,6 +180,17 @@ private static void SetTestContainer(string testModule = null, bool disableResto
                 return serviceCollection.BuildServiceProvider();
             });
         }
+
+        private static string GetTypeFullName<T>()
+        {
+            string name = typeof(T).FullName;
+            if (typeof(T).IsGenericType && name != null)
+            {
+                int index = name.IndexOf('`');
+                return index == -1 ? name : name[..index];
+            }
+            return name;
+        }
     }
 
     class CustomProcessExitHandler : IProcessExitHandler

diff --git a/test/coverlet.core.tests/Samples/Instrumentation.GenericAsyncIterator.cs b/test/coverlet.core.tests/Samples/Instrumentation.GenericAsyncIterator.cs
@@ -0,0 +1,25 @@
+// Remember to use full name because adding new using directives change line numbers
+
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace Coverlet.Core.Samples.Tests
+{
+    public class GenericAsyncIterator<T>
+    {
+        public async Task<List<int>> Issue1383()
+        {
+            var sequence = await CreateSequenceAsync().ToListAsync();
+            return sequence;
+        }
+
+
+        public async IAsyncEnumerable<int> CreateSequenceAsync()
+        {
+            await Task.CompletedTask;
+            yield return 5;
+            yield return 2;
+        }
+    }
+}