Add ReportGenerator helper (#518)

* add report generator helper

Directory.Build.targets

@@ -12,6 +12,7 @@
     <PackageReference Update="Moq" Version="4.10.1" />
     <!-- Do not upgrade this version or we won't support old SDK -->
     <PackageReference Update="Newtonsoft.Json" Version="9.0.1" />
+    <PackageReference Update="ReportGenerator.Core" Version="4.2.15" />
     <!--
         Do not change System.Reflection.Metadata version since we need to support VSTest DataCollectors. Goto https://www.nuget.org/packages/System.Reflection.Metadata to check versions.
         We need to load assembly version 1.4.2.0 to properly work

test/coverlet.core.tests/CoverageTests.cs

@@ -96,6 +96,9 @@ namespace Coverlet.Core.Tests
                       .AssertLinesCovered((11, 1), (15, 0))
                       // (line,ordinal,hits)
                       .AssertBranchesCovered((9, 0, 1), (9, 1, 0));
+
+                // if need to generate html report for debugging purpose
+                // TestInstrumentationHelper.GenerateHtmlReport(result);
             }
             finally
             {

test/coverlet.core.tests/InstrumenterHelper.cs

@@ -3,14 +3,17 @@ using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using System.Reflection;
+using System.Runtime.CompilerServices;
 using System.Threading;
 using System.Threading.Tasks;
+
 using Coverlet.Core.Abstracts;
 using Coverlet.Core.Instrumentation;
 using Coverlet.Core.Logging;
+using Coverlet.Core.Reporters;
 using Microsoft.Extensions.DependencyInjection;
 using Moq;
-using Xunit;
+using Palmmedia.ReportGenerator.Core;
 using Xunit.Sdk;
 
 namespace Coverlet.Core.Tests
@@ -107,6 +110,33 @@ namespace Coverlet.Core.Tests
 
     public static class TestInstrumentationHelper
     {
+        /// <summary>
+        /// caller sample:  TestInstrumentationHelper.GenerateHtmlReport(result, sourceFileFilter: @"+**\Samples\Instrumentation.cs");
+        ///                 TestInstrumentationHelper.GenerateHtmlReport(result);
+        /// </summary>
+        public static void GenerateHtmlReport(CoverageResult coverageResult, IReporter reporter = null, string sourceFileFilter = "", [CallerMemberName]string directory = "")
+        {
+            reporter ??= new CoberturaReporter();
+            DirectoryInfo dir = Directory.CreateDirectory(directory);
+            dir.Delete(true);
+            dir.Create();
+            string reportFile = Path.Combine(dir.FullName, Path.ChangeExtension("report", reporter.Extension));
+            File.WriteAllText(reportFile, reporter.Report(coverageResult));
+            // i.e. reportgenerator -reports:"C:\git\coverlet\test\coverlet.core.tests\bin\Debug\netcoreapp2.0\Condition_If\report.cobertura.xml" -targetdir:"C:\git\coverlet\test\coverlet.core.tests\bin\Debug\netcoreapp2.0\Condition_If" -filefilters:+**\Samples\Instrumentation.cs
+            new Generator().GenerateReport(new ReportConfiguration(
+            new[] { reportFile },
+            dir.FullName,
+            new string[0],
+            null,
+            new string[0],
+            new string[0],
+            new string[0],
+            new string[0],
+            string.IsNullOrEmpty(sourceFileFilter) ? new string[0] : new[] { sourceFileFilter },
+            null,
+            null));
+        }
+
         public static CoverageResult GetCoverageResult(string filePath)
         {
             using (var result = new FileStream(filePath, FileMode.Open))

test/coverlet.core.tests/coverlet.core.tests.csproj

@@ -4,13 +4,14 @@
   <PropertyGroup>
     <TargetFramework>netcoreapp2.0</TargetFramework>
     <IsPackable>false</IsPackable>
-    <LangVersion>latest</LangVersion>
+    <LangVersion>preview</LangVersion>
   </PropertyGroup>
 
   <ItemGroup>
     <PackageReference Include="Microsoft.CodeAnalysis.CSharp" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" />
     <PackageReference Include="Moq" />
+    <PackageReference Include="ReportGenerator.Core" />
     <PackageReference Include="xunit" />
     <PackageReference Include="xunit.runner.visualstudio" />
   </ItemGroup>