restore original uninstrumented modules after coverage is run

src/coverlet.core/Coverage.cs

@@ -53,6 +53,8 @@ namespace Coverlet.Core
                 data.Add(instrumenterResult.Module, documents);
             }
 
+            InstrumentationHelper.RestoreOriginalModules(_results);
+
             return new CoverageResult
             {
                 Identifier = _identifier,

src/coverlet.core/Helpers/InstrumentationHelper.cs

@@ -3,6 +3,8 @@ using System.IO;
 using System.Linq;
 using System.Reflection.PortableExecutable;
 
+using Coverlet.Core.Instrumentation;
+
 namespace Coverlet.Core.Helpers
 {
     internal static class InstrumentationHelper
@@ -32,5 +34,14 @@ namespace Coverlet.Core.Helpers
                 return false;
             }
         }
+
+        public static void RestoreOriginalModules(IEnumerable<InstrumenterResult> results)
+        {
+            foreach (var result in results)
+            {
+                File.Copy(result.OriginalModuleTempPath, result.OriginalModulePath, true);
+                File.Delete(result.OriginalModuleTempPath);
+            }
+        }
     }
 }

src/coverlet.core/Instrumentation/Instrumenter.cs

@@ -27,10 +27,19 @@ namespace Coverlet.Core.Instrumentation
                 Path.GetFileNameWithoutExtension(_module) + "_" + _identifier
             );
 
+            string originalModuleTempPath = Path.Combine(
+                Path.GetTempPath(),
+                Path.GetFileNameWithoutExtension(_module) + "_" + _identifier + ".dll"
+            );
+
+            File.Copy(_module, originalModuleTempPath);
+
             _result = new InstrumenterResult
             {
                 Module = Path.GetFileNameWithoutExtension(_module),
-                ReportPath = reportPath
+                ReportPath = reportPath,
+                OriginalModulePath = _module,
+                OriginalModuleTempPath = originalModuleTempPath
             };
 
             InstrumentModule();

src/coverlet.core/Instrumentation/InstrumenterResult.cs

@@ -21,6 +21,8 @@ namespace Coverlet.Core.Instrumentation
         public InstrumenterResult() => Documents = new List<Document>();
         public string Module;
         public string ReportPath;
+        public string OriginalModulePath;
+        public string OriginalModuleTempPath;
         public List<Document> Documents { get; private set; }
     }
 }