Negative coverage when integer overflows

Documentation/Changelog.md

@@ -6,7 +6,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
-### Fixed 
+### Fixed
+-Fix negative coverage exceeding int.MaxValue [#1266](https://github.com/coverlet-coverage/coverlet/issues/1266)
 -Fix summary output format for culture de-DE [#1263](https://github.com/coverlet-coverage/coverlet/issues/1263)
 -Fix branch coverage issue for finally block with await [#1233](https://github.com/coverlet-coverage/coverlet/issues/1233)  
 -Fix threshold doesn't work when coverage empty [#1205](https://github.com/coverlet-coverage/coverlet/issues/1205)  

src/coverlet.core/Coverage.cs

@@ -421,10 +421,18 @@ private void CalculateCoverage()
                         var document = documentsList[hitLocation.docIndex];
                         int hits = br.ReadInt32();
 
+                        if (hits == 0)
+                            continue;
+
+                        hits = hits < 0 ? int.MaxValue : hits;
+
                         if (hitLocation.isBranch)
                         {
                             var branch = document.Branches[new BranchKey(hitLocation.start, hitLocation.end)];
                             branch.Hits += hits;
+
+                            if (branch.Hits < 0)
+                                branch.Hits = int.MaxValue;
                         }
                         else
                         {
@@ -437,6 +445,9 @@ private void CalculateCoverage()
 
                                 var line = document.Lines[j];
                                 line.Hits += hits;
+
+                                if (line.Hits < 0)
+                                    line.Hits = int.MaxValue;
                             }
                         }
                     }

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

@@ -0,0 +1,65 @@
+using System.IO;
+using Coverlet.Core.Abstractions;
+using Coverlet.Core.Instrumentation;
+using Moq;
+using Xunit;
+
+namespace Coverlet.Core.Tests
+{
+    public partial class CoverageTests
+    {
+        [Fact]
+        public void CoverageResult_NegativeLineCoverage_TranslatedToMaxValueOfInt32()
+        {
+            InstrumenterResult instrumenterResult = new InstrumenterResult
+            {
+                HitsFilePath = "HitsFilePath", 
+                SourceLink = "SourceLink", 
+                ModulePath = "ModulePath"
+            };
+
+            instrumenterResult.HitCandidates.Add(new HitCandidate(false, 0, 1, 1));
+
+            var document = new Document
+            {
+                Index = 0,
+                Path = "Path0"
+            };
+
+            document.Lines.Add(1, new Line
+            {
+                Class = "Class0",
+                Hits = 0,
+                Method = "Method0",
+                Number = 1
+            });
+
+            instrumenterResult.Documents.Add("document", document);
+
+            CoveragePrepareResult coveragePrepareResult = new CoveragePrepareResult
+            {
+                UseSourceLink = true, 
+                Results = new[] {instrumenterResult}, 
+                Parameters = new CoverageParameters()
+            };
+
+            Stream memoryStream = new MemoryStream();
+            BinaryWriter binaryWriter = new BinaryWriter(memoryStream);
+            binaryWriter.Write(1);
+            binaryWriter.Write(-1);
+            memoryStream.Position = 0;
+
+            var fileSystemMock = new Mock<IFileSystem>();
+            fileSystemMock.Setup(x => x.Exists(It.IsAny<string>())).Returns(true);
+            fileSystemMock.Setup(x => x.NewFileStream(It.IsAny<string>(), FileMode.Open, FileAccess.Read))
+                .Returns(memoryStream);
+
+            var coverage = new Coverage(coveragePrepareResult, new Mock<ILogger>().Object, new Mock<IInstrumentationHelper>().Object,
+                fileSystemMock.Object, new Mock<ISourceRootTranslator>().Object);
+
+            var coverageResult = coverage.GetCoverageResult();
+            coverageResult.Document("document").AssertLinesCovered(BuildConfiguration.Debug, (1, int.MaxValue));
+
+        }
+    }
+}