Add new method to manually call the unloading of modules

Author: Joseph Sun

src/coverlet.collector/DataCollection/CoverageWrapper.cs

@@ -70,5 +70,10 @@ public void PrepareModules(Coverage coverage)
     {
       coverage.PrepareModules();
     }
+
+    public void UnloadModule(Coverage coverage, string modulePath)
+    {
+      coverage.UnloadModule(modulePath);
+    }
   }
 }

src/coverlet.collector/Utilities/Interfaces/ICoverageWrapper.cs

@@ -39,5 +39,11 @@ internal interface ICoverageWrapper
     /// <param name="coverage"></param>
     void PrepareModules(Coverage coverage);
 
+    /// <summary>
+    /// Unload module in the specified path
+    /// </summary>
+    /// <param name="modulePath"></param>
+    void UnloadModule(Coverage coverage, string modulePath);
+
   }
 }

src/coverlet.core/Coverage.cs

@@ -59,6 +59,7 @@ internal class Coverage
     private readonly CoverageParameters _parameters;
 
     public string Identifier { get; }
+    private List<string> unloadedModules { get; set; }
 
     public Coverage(string moduleOrDirectory,
         CoverageParameters parameters,
@@ -78,6 +79,7 @@ public Coverage(string moduleOrDirectory,
       _cecilSymbolHelper = cecilSymbolHelper;
       Identifier = Guid.NewGuid().ToString();
       _results = new List<InstrumenterResult>();
+      unloadedModules = new List<string>();
     }
 
     public Coverage(CoveragePrepareResult prepareResult,
@@ -241,7 +243,10 @@ public CoverageResult GetCoverageResult()
         }
 
         modules.Add(Path.GetFileName(result.ModulePath), documents);
-        _instrumentationHelper.RestoreOriginalModule(result.ModulePath, Identifier);
+        if (!unloadedModules.Contains(result.ModulePath))
+        {
+          UnloadModule(result.ModulePath);
+        }
       }
 
       // In case of anonymous delegate compiler generate a custom class and passes it as type.method delegate.
@@ -326,6 +331,16 @@ public CoverageResult GetCoverageResult()
       return coverageResult;
     }
 
+    /// <summary>
+    /// Manually invoke the unloading of modules and restoration of the original assembly files
+    /// </summary>
+    /// <param name="modulePath"></param>
+    public void UnloadModule(string modulePath)
+    {
+      unloadedModules.Add(modulePath);
+      _instrumentationHelper.RestoreOriginalModule(modulePath, Identifier);
+    }
+
     private bool BranchInCompilerGeneratedClass(string methodName)
     {
       foreach (InstrumenterResult instrumentedResult in _results)