[generator] Revert change to use auto-properties in EventArgs classes (#736)

In ee7afee, properties in generated EventArgs classes were changed
from regular properties:

	int param1;
	public int Param1 {
	    get { return param1; }
	}

to instead emit auto-properties:

	public int Param1 { get; }

However, this is technically a source breaking change, since users
could have hand written code that references the backing field.
Although the usage is likely rare, we have decided to revert the
auto-property change for compatibility reasons.

Author: jpobst

tests/generator-Tests/Unit-Tests/CodeGeneratorExpectedResults/Common/WriteDuplicateInterfaceEventArgs.txt

@@ -123,24 +123,37 @@ internal partial class AnimatorListenerInvoker : global::Java.Lang.Object, Anima
 
 // event args for java.code.AnimatorListener.OnAnimationEnd
 public partial class AnimationEndEventArgs : global::System.EventArgs {
+	bool handled;
+
+	public bool Handled {
+		get { return handled; }
+		set { handled = value; }
+	}
+
 	public AnimationEndEventArgs (bool handled, int param1)
 	{
-		this.Handled = handled;
-		this.Param1 = param1;
+		this.handled = handled;
+		this.param1 = param1;
+	}
+
+	int param1;
+
+	public int Param1 {
+		get { return param1; }
 	}
 
 	public AnimationEndEventArgs (bool handled, int param1, int param2)
 	{
-		this.Handled = handled;
-		this.Param1 = param1;
-		this.Param2 = param2;
+		this.handled = handled;
+		this.param1 = param1;
+		this.param2 = param2;
 	}
 
-	public bool Handled { get; set; }
+	int param2;
 
-	public int Param1 { get; private set; }
-
-	public int Param2 { get; private set; }
+	public int Param2 {
+		get { return param2; }
+	}
 
 }
 

tests/generator-Tests/expected.ji/GenericArguments/Com.Google.Android.Exoplayer.Drm.IExoMediaDrm.cs

@@ -123,22 +123,42 @@ public unsafe void OnEvent (global::Com.Google.Android.Exoplayer.Drm.IExoMediaDr
 	public partial class ExoMediaDrmOnEventEventArgs : global::System.EventArgs {
 		public ExoMediaDrmOnEventEventArgs (global::Com.Google.Android.Exoplayer.Drm.IExoMediaDrm p0, byte[] p1, int p2, int p3, byte[] p4)
 		{
-			this.P0 = p0;
-			this.P1 = p1;
-			this.P2 = p2;
-			this.P3 = p3;
-			this.P4 = p4;
+			this.p0 = p0;
+			this.p1 = p1;
+			this.p2 = p2;
+			this.p3 = p3;
+			this.p4 = p4;
 		}
 
-		public global::Com.Google.Android.Exoplayer.Drm.IExoMediaDrm P0 { get; private set; }
+		global::Com.Google.Android.Exoplayer.Drm.IExoMediaDrm p0;
 
-		public byte[] P1 { get; private set; }
+		public global::Com.Google.Android.Exoplayer.Drm.IExoMediaDrm P0 {
+			get { return p0; }
+		}
+
+		byte[] p1;
+
+		public byte[] P1 {
+			get { return p1; }
+		}
+
+		int p2;
 
-		public int P2 { get; private set; }
+		public int P2 {
+			get { return p2; }
+		}
+
+		int p3;
 
-		public int P3 { get; private set; }
+		public int P3 {
+			get { return p3; }
+		}
 
-		public byte[] P4 { get; private set; }
+		byte[] p4;
+
+		public byte[] P4 {
+			get { return p4; }
+		}
 
 	}
 

tools/generator/SourceWriters/InterfaceEventArgsClass.cs

@@ -18,18 +18,12 @@ public InterfaceEventArgsClass (InterfaceGen iface, Method method)
 			IsPublic = true;
 			IsPartial = true;
 
+			UsePriorityOrder = true;
+
 			Comments.Add ($"// event args for {iface.JavaName}.{method.JavaName}");
 
-			// Add: public bool Handled { get; set; }
 			if (method.IsEventHandlerWithHandledProperty)
-				Properties.Add (new PropertyWriter {
-					Name = "Handled",
-					PropertyType = TypeReferenceWriter.Bool,
-					IsPublic = true,
-					HasGet = true,
-					HasSet = true,
-					IsAutoProperty = true
-				});
+				Properties.Add (new HandledProperty ());
 		}
 
 		public void AddMembersFromMethod (InterfaceGen iface, Method method, CodeGenerationOptions opt)
@@ -47,15 +41,15 @@ void AddConstructor (InterfaceGen iface, Method method, CodeGenerationOptions op
 
 			if (method.IsEventHandlerWithHandledProperty) {
 				ctor.Parameters.Add (new MethodParameterWriter ("handled", TypeReferenceWriter.Bool));
-				ctor.Body.Add ("this.Handled = handled;");
+				ctor.Body.Add ("this.handled = handled;");
 			}
 
 			foreach (var p in method.Parameters) {
 				if (p.IsSender)
 					continue;
 
 				ctor.Parameters.Add (new MethodParameterWriter (p.Name, new TypeReferenceWriter (opt.GetTypeReferenceName (p))));
-				ctor.Body.Add ($"this.{p.PropertyName} = {opt.GetSafeIdentifier (p.Name)};");
+				ctor.Body.Add ($"this.{opt.GetSafeIdentifier (p.Name)} = {opt.GetSafeIdentifier (p.Name)};");
 			}
 
 			Constructors.Add (ctor);
@@ -71,18 +65,47 @@ void AddProperties (Method method, CodeGenerationOptions opt)
 				if (Properties.Any (prop => prop.Name == p.PropertyName))
 					continue;
 
+				Fields.Add (new FieldWriter {
+					Name = opt.GetSafeIdentifier (p.Name),
+					Type = new TypeReferenceWriter (opt.GetTypeReferenceName (p))
+				});
+
 				var prop = new PropertyWriter {
 					Name = p.PropertyName,
 					PropertyType = new TypeReferenceWriter (opt.GetTypeReferenceName (p)),
 					IsPublic = true,
-					HasGet = true,
-					HasSet = true,
-					IsAutoProperty = true,
-					AutoSetterVisibility = Visibility.Private
+					HasGet = true
 				};
 
+				prop.GetBody.Add ($"return {opt.GetSafeIdentifier (p.Name)};");
+
 				Properties.Add (prop);
 			}
 		}
 	}
+
+	public class HandledProperty : PropertyWriter
+	{
+		public HandledProperty ()
+		{
+			Name = "Handled";
+			PropertyType = TypeReferenceWriter.Bool;
+
+			IsPublic = true;
+
+			HasGet = true;
+			GetBody.Add ("return handled;");
+
+			HasSet = true;
+			SetBody.Add ("handled = value;");
+		}
+
+		public override void Write (CodeWriter writer)
+		{
+			writer.WriteLine ("bool handled;");
+			writer.WriteLine ();
+
+			base.Write (writer);
+		}
+	}
 }