Support .NET language features: init only setter (#619)

Author: huangmin-ms

mdoc/Consts.cs

@@ -50,5 +50,6 @@ public static class Consts
         public const string IsReadOnlyAttribute = "System.Runtime.CompilerServices.IsReadOnlyAttribute";
         public const string InAttribute = "System.Runtime.InteropServices.InAttribute";
         public const string TupleElementNamesAttribute = "System.Runtime.CompilerServices.TupleElementNamesAttribute";
+        public const string IsExternalInit = "System.Runtime.CompilerServices.IsExternalInit";
     }
 }

mdoc/Mono.Documentation/Updater/Formatters/CSharpFullMemberFormatter.cs

@@ -725,7 +725,14 @@ protected override string GetPropertyDeclaration (PropertyDefinition property)
             {
                 if (set_visible != visibility)
                     buf.Append (' ').Append (set_visible);
-                buf.Append (" set;");
+                if (property.SetMethod.ReturnType is RequiredModifierType returnType && returnType.ModifierType.FullName == Consts.IsExternalInit)
+                {
+                    buf.Append(" init;");
+                }
+                else
+                {
+                    buf.Append(" set;");
+                }
             }
             buf.Append (" }");
 

mdoc/mdoc.Test/FormatterTests.cs

@@ -453,6 +453,17 @@ public void CSharpTupleNamesMethodTest(string methodName, string expectedSignatu
             Assert.AreEqual(expectedSignature, methodSignature);
         }
 
+        [TestCase("Property1", "public int Property1 { get; set; }")]
+        [TestCase("Property2", "public int Property2 { get; init; }")]
+        [TestCase("Property3", "public int Property3 { get; protected init; }")]
+        [TestCase("Item", "public int this[int index] { get; init; }")]
+        public void CSharpInitOnlySetterTest(string propertyName, string expectedSignature)
+        {
+            var property = GetProperty(typeof(SampleClasses.InitOnlySetter), p => p.Name == propertyName);
+            var propertySignature = formatter.GetDeclaration(property);
+            Assert.AreEqual(expectedSignature, propertySignature);
+        }
+
         #region Helper Methods
         string RealTypeName(string name){
             switch (name) {

mdoc/mdoc.Test/SampleClasses/InitOnlySetter.cs

@@ -0,0 +1,20 @@
+namespace mdoc.Test.SampleClasses
+{
+    public class InitOnlySetter
+    {
+        public int Property1 { get; set; }
+        public int Property2 { get; init; }
+        public int Property3 { get; protected init; }
+        public int this[int index]
+        {
+            get
+            {
+                throw null;
+            }
+            init
+            {
+                throw null;
+            }
+        }
+    }
+}

mdoc/mdoc.Test/SampleClasses/IsExternalInit.cs

@@ -0,0 +1,7 @@
+using System.ComponentModel;
+
+namespace System.Runtime.CompilerServices
+{
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    internal class IsExternalInit { }
+}