Add Null static field to handles

microsoft · Aug 5, 2022 · cdee3e4 · cdee3e4
1 parent 39757ab
commit cdee3e4
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Showing 2 changed files with 17 additions and 0 deletions.
diff --git a/src/Microsoft.Windows.CsWin32/Generator.cs b/src/Microsoft.Windows.CsWin32/Generator.cs
@@ -3885,6 +3885,12 @@ private IEnumerable<MemberDeclarationSyntax> CreateCommonTypeDefMembers(Identifi
         // If this typedef struct represents a pointer, add an IsNull property.
         if (fieldType is IdentifierNameSyntax { Identifier: { Value: nameof(IntPtr) or nameof(UIntPtr) } })
         {
+            // public static readonly IntPtr Null;
+            yield return FieldDeclaration(VariableDeclaration(structName.WithTrailingTrivia(TriviaList(Space)))
+                .AddVariables(VariableDeclarator(IdentifierName("Null").Identifier)))
+                .AddModifiers(TokenWithSpace(SyntaxKind.PublicKeyword), TokenWithSpace(SyntaxKind.StaticKeyword), TokenWithSpace(SyntaxKind.ReadOnlyKeyword)) // operators MUST be public
+                .WithSemicolonToken(SemicolonWithLineFeed);
+
             // internal static bool IsNull => value == default;
             yield return PropertyDeclaration(PredefinedType(TokenWithSpace(SyntaxKind.BoolKeyword)), "IsNull")
                 .AddModifiers(TokenWithSpace(this.Visibility))

diff --git a/test/Microsoft.Windows.CsWin32.Tests/GeneratorTests.cs b/test/Microsoft.Windows.CsWin32.Tests/GeneratorTests.cs
@@ -587,6 +587,17 @@ public void HandleStructsHaveIsNullProperty(string handleName)
         this.AssertGeneratedMember(handleName, "IsNull", "internal bool IsNull => Value == default;");
     }
 
+    [Theory]
+    [InlineData("HANDLE")]
+    [InlineData("HGDIOBJ")]
+    [InlineData("HINSTANCE")]
+    public void HandleStructsHaveStaticNullField(string handleName)
+    {
+        // A null HGDIOBJ has a specific meaning beyond just the concept of an invalid handle:
+        // https://docs.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-selectobject#return-value
+        this.AssertGeneratedMember(handleName, "Null", "Null");
+    }
+
     [Theory]
     [InlineData("HANDLE")]
     [InlineData("HGDIOBJ")]