Change PS to load the assembly with 'Assembly.LoadFrom' before 'Assembly.Load' when the file path is given (PowerShell#4196)

It's to solve a side-by-side problem we have with powershell core. If a .NET Core version assembly has the same name as it's .NET ancestor in GAC, then even if you specify the file path to `Import-Module`, powershell core will still load the one in GAC because it tries 'Assembly.Load' first.
Now we change it to use `Assembly.LoadFrom` first when a file path is given, so it works for modules that have side-by-side assemblies.

Author: chunqingchen

src/System.Management.Automation/engine/ExecutionContext.cs

@@ -1322,110 +1322,72 @@ internal void RemoveAssembly(string name)
         [SuppressMessage("Microsoft.Reliability", "CA2001:AvoidCallingProblematicMethods", MessageId = "System.Reflection.Assembly.LoadFrom")]
         internal static Assembly LoadAssembly(string name, string filename, out Exception error)
         {
-            // First we try to load the assembly based on the given name
-
-            Assembly loadedAssembly = null;
-            error = null;
-
-            string fixedName = null;
-            if (!String.IsNullOrEmpty(name))
-            {
-                // Remove the '.dll' if it's there...
-                fixedName = name.EndsWith(".dll", StringComparison.OrdinalIgnoreCase)
-                                ? Path.GetFileNameWithoutExtension(name)
-                                : name;
-
-                var assemblyString = Utils.IsPowerShellAssembly(fixedName)
-                                         ? Utils.GetPowerShellAssemblyStrongName(fixedName)
-                                         : fixedName;
-
-                try
-                {
-                    loadedAssembly = Assembly.Load(new AssemblyName(assemblyString));
-                }
-                catch (FileNotFoundException fileNotFound)
-                {
-                    error = fileNotFound;
-                }
-                catch (FileLoadException fileLoadException)
-                {
-                    error = fileLoadException;
-                    // this is a legitimate error on CoreCLR for a newly emited with Add-Type assemblies
-                    // they cannot be loaded by name, but we are only interested in importing them by path
-                }
-                catch (BadImageFormatException badImage)
-                {
-                    error = badImage;
-                    return null;
-                }
-                catch (SecurityException securityException)
-                {
-                    error = securityException;
-                    return null;
-                }
-            }
-
-            if (loadedAssembly != null)
-                return loadedAssembly;
-
-            if (!String.IsNullOrEmpty(filename))
-            {
-                error = null;
-
-                try
-                {
-                    loadedAssembly = Assembly.LoadFrom(filename);
-                    return loadedAssembly;
-                }
-                catch (FileNotFoundException fileNotFound)
-                {
-                    error = fileNotFound;
-                }
-                catch (FileLoadException fileLoadException)
-                {
-                    error = fileLoadException;
-                    return null;
-                }
-                catch (BadImageFormatException badImage)
-                {
-                    error = badImage;
-                    return null;
-                }
-                catch (SecurityException securityException)
-                {
-                    error = securityException;
-                    return null;
-                }
-            }
-
-#if !CORECLR// Assembly.LoadWithPartialName is not in CoreCLR. In CoreCLR, 'LoadWithPartialName' can be replaced by Assembly.Load with the help of AssemblyLoadContext.
-            // Finally try with partial name...
-            if (!String.IsNullOrEmpty(fixedName))
-            {
-                try
-                {
-                    // This is a deprecated API, use of this API needs to be
-                    // reviewed periodically.
-#pragma warning disable 0618
-                    loadedAssembly = Assembly.LoadWithPartialName(fixedName);
-
-                    if (loadedAssembly != null)
-                    {
-                        // In the past, LoadWithPartialName would just return null in most cases when the assembly could not be found or loaded.
-                        // In addition to this, the error was always cleared. So now, clear the error variable only if the assembly was loaded.
-                        error = null;
-                    }
-                    return loadedAssembly;
-                }
-
-                // Expected exceptions are ArgumentNullException and BadImageFormatException. See https://msdn.microsoft.com/en-us/library/12xc5368(v=vs.110).aspx
-                catch (BadImageFormatException badImage)
-                {
-                    error = badImage;
-                }
-            }
-#endif
-            return null;
+            // First we try to load the assembly based on the filename
+
+            Assembly loadedAssembly = null;
+            error = null;
+
+            if (!String.IsNullOrEmpty(filename))
+            {
+                try
+                {
+                    loadedAssembly = Assembly.LoadFrom(filename);
+                }
+                catch (FileNotFoundException fileNotFound)
+                {
+                    error = fileNotFound;
+                }
+                catch (FileLoadException fileLoadException)
+                {
+                    error = fileLoadException;
+                }
+                catch (BadImageFormatException badImage)
+                {
+                    error = badImage;
+                }
+                catch (SecurityException securityException)
+                {
+                    error = securityException;
+                }
+            }
+            else if (!String.IsNullOrEmpty(name))
+            {
+                string fixedName = null;
+                // Remove the '.dll' if it's there...
+                fixedName = name.EndsWith(".dll", StringComparison.OrdinalIgnoreCase)
+                                ? Path.GetFileNameWithoutExtension(name)
+                                : name;
+
+                var assemblyString = Utils.IsPowerShellAssembly(fixedName)
+                                         ? Utils.GetPowerShellAssemblyStrongName(fixedName)
+                                         : fixedName;
+
+                try
+                {
+                    loadedAssembly = Assembly.Load(new AssemblyName(assemblyString));
+                }
+                catch (FileNotFoundException fileNotFound)
+                {
+                    error = fileNotFound;
+                }
+                catch (FileLoadException fileLoadException)
+                {
+                    error = fileLoadException;
+                    // this is a legitimate error on CoreCLR for a newly emited with Add-Type assemblies
+                    // they cannot be loaded by name, but we are only interested in importing them by path
+                }
+                catch (BadImageFormatException badImage)
+                {
+                    error = badImage;
+                }
+                catch (SecurityException securityException)
+                {
+                    error = securityException;
+                }
+            }
+
+            // We either return the loaded Assembly, or return null.
+            return loadedAssembly;
         }
 
         /// <summary>

test/powershell/Modules/Microsoft.PowerShell.Core/Import-Module.Tests.ps1

@@ -94,3 +94,33 @@ Describe "Import-Module for Binary Modules in GAC" -Tags 'CI' {
         }
     }
 }
+
+Describe "Import-Module for Binary Modules" -Tags 'CI' {
+
+    It "PS should try to load the assembly from file path first" {
+ $src = @"
+using System.Management.Automation;           // Windows PowerShell namespace.
+
+namespace ModuleCmdlets
+{
+  [Cmdlet(VerbsDiagnostic.Test,"BinaryModuleCmdlet1")]   
+  public class TestBinaryModuleCmdlet1Command : Cmdlet
+  {
+    protected override void BeginProcessing()
+    {
+      WriteObject("BinaryModuleCmdlet1 exported by the ModuleCmdlets module.");
+    }
+  }
+}
+"@
+
+    Add-Type -TypeDefinition $src -OutputAssembly $TESTDRIVE\System.dll
+    $results = powershell -noprofile -c "`$module = Import-Module $TESTDRIVE\System.dll -Passthru; `$module.ImplementingAssembly.Location; Test-BinaryModuleCmdlet1"
+
+    #Ignore slash format difference under windows/Unix
+    $path = (Get-ChildItem $TESTDRIVE\System.dll).FullName
+    $results[0] | Should Be $path
+    $results[1] | Should BeExactly "BinaryModuleCmdlet1 exported by the ModuleCmdlets module."
+    }
+ }
+