Fix ArgumentNullException in IronPython forms designer when a form has a button, a timer and only the timer's Tick event handler is specified.

src/AddIns/BackendBindings/Python/PythonBinding/Project/Src/PythonComponentWalker.cs

@@ -165,7 +165,7 @@ namespace ICSharpCode.PythonBinding
 			
 			MemberExpression eventExpression = node.Left as MemberExpression;
 			string eventName = eventExpression.Name.ToString();
-			PythonControlFieldExpression field = PythonControlFieldExpression.Create(eventExpression);
+			fieldExpression = PythonControlFieldExpression.Create(eventExpression);
 			
 			MemberExpression eventHandlerExpression = node.Right as MemberExpression;
 			string eventHandlerName = eventHandlerExpression.Name.ToString();

src/AddIns/BackendBindings/Python/PythonBinding/Test/Designer/LoadFormWithButtonFollowedByTimerTestFixture.cs

@@ -0,0 +1,108 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Drawing;
+using System.IO;
+using System.Windows.Forms;
+
+using ICSharpCode.PythonBinding;
+using ICSharpCode.Scripting.Tests.Utils;
+using NUnit.Framework;
+using PythonBinding.Tests.Utils;
+
+namespace PythonBinding.Tests.Designer
+{
+	/// <summary>
+	/// Fix ArgumentNullException when form has a button followed by a timer and the
+	/// first timer statement is the setting of the event handler.
+	/// </summary>
+	[TestFixture]
+	public class LoadFormWithButtonFollowedByTimerTestFixture : LoadFormTestFixtureBase
+	{
+		MockPropertyDescriptor mockTickPropertyDescriptor;
+		
+		public override string PythonCode {
+			get {
+				return
+					"import System.Drawing\r\n" +
+					"import System.Windows.Forms\r\n" +
+					"\r\n" +
+					"from System.Drawing import *\r\n" +
+					"from System.Windows.Forms import *\r\n" +
+					"\r\n" +
+					"class MainForm(Form):\r\n" +
+					"    def __init__(self):\r\n" +
+					"        self.InitializeComponent()\r\n" +
+					"\r\n" +
+					"    def InitializeComponent(self):\r\n" +
+					"        self._components = System.ComponentModel.Container()\r\n" +
+					"        self._button1 = System.Windows.Forms.Button()\r\n" +
+					"        self._timer1 = System.Windows.Forms.Timer(self._components)\r\n" +
+					"        self.SuspendLayout()\r\n" +
+					"        # \r\n" +
+					"        # button1\r\n" +
+					"        # \r\n" +
+					"        self._button1.Location = System.Drawing.Point(37, 29)\r\n" +
+					"        self._button1.Name = \"button1\"\r\n" +
+					"        self._button1.Size = System.Drawing.Size(75, 23)\r\n" +
+					"        self._button1.TabIndex = 0\r\n" +
+					"        self._button1.Text = \"button1\"\r\n" +
+					"        self._button1.UseVisualStyleBackColor = True\r\n" +
+					"        # \r\n" +
+					"        # timer1\r\n" +
+					"        # \r\n" +
+					"        self._timer1.Tick += self.Timer1Tick\r\n" +
+					"        # \r\n" +
+					"        # MainForm\r\n" +
+					"        # \r\n" +
+					"        self.ClientSize = System.Drawing.Size(284, 264)\r\n" +
+					"        self.Controls.Add(self._button1)\r\n" +
+					"        self.Name = \"MainForm\"\r\n" +
+					"        self.Text = \"PyWinTest\"\r\n" +
+					"        self.ResumeLayout(False)\r\n" +
+					"\r\n" +
+					"\r\n" +
+					"    def Timer1Tick(self, sender, e):\r\n" +
+					"        pass";
+			}
+		}
+		
+		public override void BeforeSetUpFixture()
+		{
+			mockTickPropertyDescriptor = new MockPropertyDescriptor("Tick", null, false);
+			ComponentCreator.SetEventPropertyDescriptor(mockTickPropertyDescriptor);
+		}
+		
+		[Test]
+		public void EventDescriptorUsedToGetEventProperty()
+		{
+			Assert.IsNotNull(ComponentCreator.EventDescriptorPassedToGetEventProperty);
+		}
+		
+		[Test]
+		public void EventDescriptorNameUsedToGetEventPropertyIsTick()
+		{
+			Assert.AreEqual("Tick", ComponentCreator.EventDescriptorPassedToGetEventProperty.Name);
+		}
+		
+		[Test]
+		public void GetPropertyValueSetForTimer()
+		{
+			string value = mockTickPropertyDescriptor.GetValue(null) as String;
+			Assert.AreEqual("Timer1Tick", value);
+		}
+		
+		[Test]
+		public void GetComponentUsedWhenSettingTickHandler()
+		{
+			IComponent expectedComponent = ComponentCreator.GetComponent("timer1");
+			
+			object component = mockTickPropertyDescriptor.GetSetValueComponent();
+			
+			Assert.AreEqual(expectedComponent, component);
+		}
+	}
+}

src/AddIns/BackendBindings/Python/PythonBinding/Test/PythonBinding.Tests.csproj

@@ -265,6 +265,7 @@
     <Compile Include="Designer\LoadFontTestFixture.cs" />
     <Compile Include="Designer\LoadFormTestFixtureBase.cs" />
     <Compile Include="Designer\LoadFormWithBooleanPropertiesSetTestFixture.cs" />
+    <Compile Include="Designer\LoadFormWithButtonFollowedByTimerTestFixture.cs" />
     <Compile Include="Designer\LoadFormWithSysPathAppendStatementTestFixture.cs" />
     <Compile Include="Designer\LoadInheritedProtectedPanelFormTestFixture.cs" />
     <Compile Include="Designer\LoadInheritedPublicPanelFormTestFixture.cs" />