[release/v7.4.2] Fix PowerShell class to support deriving from an abstract class with abstract properties (#21331) (#21422)

src/System.Management.Automation/engine/parser/PSType.cs

@@ -276,7 +276,7 @@ namespace System.Management.Automation.Language
             internal readonly TypeBuilder _staticHelpersTypeBuilder;
             private readonly Dictionary<string, PropertyMemberAst> _definedProperties;
             private readonly Dictionary<string, List<Tuple<FunctionMemberAst, Type[]>>> _definedMethods;
-            private HashSet<Tuple<string, Type>> _interfaceProperties;
+            private HashSet<Tuple<string, Type>> _abstractProperties;
             internal readonly List<(string fieldName, IParameterMetadataProvider bodyAst, bool isStatic)> _fieldsToInitForMemberFunctions;
             private bool _baseClassHasDefaultCtor;
 
@@ -446,9 +446,9 @@ namespace System.Management.Automation.Language
 
             private bool ShouldImplementProperty(string name, Type type)
             {
-                if (_interfaceProperties == null)
+                if (_abstractProperties == null)
                 {
-                    _interfaceProperties = new HashSet<Tuple<string, Type>>();
+                    _abstractProperties = new HashSet<Tuple<string, Type>>();
                     var allInterfaces = new HashSet<Type>();
 
                     // TypeBuilder.GetInterfaces() returns only the interfaces that was explicitly passed to its constructor.
@@ -467,12 +467,23 @@ namespace System.Management.Automation.Language
                     {
                         foreach (var property in interfaceType.GetProperties())
                         {
-                            _interfaceProperties.Add(Tuple.Create(property.Name, property.PropertyType));
+                            _abstractProperties.Add(Tuple.Create(property.Name, property.PropertyType));
+                        }
+                    }
+
+                    if (_typeBuilder.BaseType.IsAbstract)
+                    {
+                        foreach (var property in _typeBuilder.BaseType.GetProperties())
+                        {
+                            if (property.GetAccessors().Any(m => m.IsAbstract))
+                            {
+                                _abstractProperties.Add(Tuple.Create(property.Name, property.PropertyType));
+                            }
                         }
                     }
                 }
 
-                return _interfaceProperties.Contains(Tuple.Create(name, type));
+                return _abstractProperties.Contains(Tuple.Create(name, type));
             }
 
             public void DefineMembers()

test/powershell/Language/Classes/scripting.Classes.inheritance.tests.ps1

@@ -628,3 +628,47 @@ class Derived : Base
         $sb.Invoke() | Should -Be 200
     }
 }
+
+Describe 'Base type has abstract properties' -Tags "CI" {
+    It 'can derive from `FileSystemInfo`' {
+        ## FileSystemInfo has 3 abstract members that a derived type needs to implement
+        ##  - public abstract bool Exists { get; }
+        ##  - public abstract string Name { get; }
+        ##  - public abstract void Delete ();
+
+        class myFileSystemInfo : System.IO.FileSystemInfo
+        {
+            [string] $Name
+            [bool] $Exists
+
+            myFileSystemInfo([string]$path)
+            {
+                # ctor
+                $this.Name = $path
+                $this.Exists = $true
+            }
+
+            [void] Delete()
+            {
+            }
+        }
+
+        $myFile = [myFileSystemInfo]::new('Hello')
+        $myFile.Name | Should -Be 'Hello'
+        $myFile.Exists | Should -BeTrue
+    }
+
+    It 'deriving from `FileSystemInfo` will fail when the abstract property `Exists` is not implemented' {
+        $script = [scriptblock]::Create('class WillFail : System.IO.FileSystemInfo { [string] $Name }')
+        $failure = $null
+        try {
+            & $script
+        } catch {
+            $failure = $_
+        }
+
+        $failure | Should -Not -BeNullOrEmpty
+        $failure.FullyQualifiedErrorId | Should -BeExactly "TypeCreationError"
+        $failure.Exception.Message | Should -BeLike "*'get_Exists'*"
+    }
+}