Add opt-in SortSwitchSections setting (#3749). (#3750)

When enabled, switch sections are ordered by their case label value
instead of by the underlying branch's IL offset. Default is false to
keep existing output unchanged. Useful when diffing decompiler output
across rebuilds of obfuscated assemblies, where IL block layout is
unstable but the case-to-value mapping is not.

Includes an ILPretty test that exercises a hand-written switch whose
table targets are placed at non-monotonic IL offsets (simulating
obfuscator block shuffling) and verifies the cases come out in
label-value order with the setting enabled. Also adds the
Resources.resx / Resources.Designer.cs entry so the WPF settings UI
shows a proper label instead of the raw key.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ICSharpCode.Decompiler.Tests/ILPrettyTestRunner.cs

@@ -339,6 +339,12 @@ namespace ICSharpCode.Decompiler.Tests
 			await Run();
 		}
 
+		[Test]
+		public async Task SortSwitchSections()
+		{
+			await Run(settings: new DecompilerSettings { SortSwitchSections = true, FileScopedNamespaces = false });
+		}
+
 		async Task Run([CallerMemberName] string testName = null, DecompilerSettings settings = null,
 			AssemblerOptions assemblerOptions = AssemblerOptions.Library)
 		{

ICSharpCode.Decompiler.Tests/TestCases/ILPretty/SortSwitchSections.cs

@@ -0,0 +1,35 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy of this
+// software and associated documentation files (the "Software"), to deal in the Software
+// without restriction, including without limitation the rights to use, copy, modify, merge,
+// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
+// to whom the Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all copies or
+// substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
+// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
+// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+namespace ICSharpCode.Decompiler.Tests.TestCases.ILPretty
+{
+	public static class SortSwitchSections
+	{
+		public static int PickValue(int n)
+		{
+			return n switch {
+				0 => 100,
+				1 => 200,
+				2 => 300,
+				3 => 400,
+				4 => 500,
+				_ => -1,
+			};
+		}
+	}
+}

ICSharpCode.Decompiler.Tests/TestCases/ILPretty/SortSwitchSections.il

@@ -0,0 +1,64 @@
+// Test fixture for the SortSwitchSections decompiler setting.
+//
+// The IL `switch` table targets are placed at non-monotonic offsets,
+// simulating obfuscator block-reordering. With SortSwitchSections=false
+// (default) the decompiler would emit cases in IL-offset order (3, 0, 4, 1, 2);
+// with the setting enabled they are emitted in label-value order (0..4).
+// The matching .cs file is the expected output with the setting enabled.
+
+.assembly extern mscorlib
+{
+  .publickeytoken = (B7 7A 5C 56 19 34 E0 89 )
+  .ver 4:0:0:0
+}
+.assembly SortSwitchSections
+{
+  .ver 1:0:0:0
+}
+.module SortSwitchSections.dll
+.imagebase 0x10000000
+.file alignment 0x00000200
+.stackreserve 0x00100000
+.subsystem 0x0003       // WINDOWS_CUI
+.corflags 0x00000001    //  ILONLY
+
+.class public auto ansi abstract sealed beforefieldinit ICSharpCode.Decompiler.Tests.TestCases.ILPretty.SortSwitchSections
+    extends [mscorlib]System.Object
+{
+    .method public hidebysig static int32 PickValue(int32 n) cil managed
+    {
+        .maxstack 1
+        IL_0000: ldarg.0
+        IL_0001: switch (
+            LBL_0,
+            LBL_1,
+            LBL_2,
+            LBL_3,
+            LBL_4)
+        IL_001a: br.s LBL_DEFAULT
+
+    LBL_3:
+        IL_001c: ldc.i4 400
+        IL_0021: ret
+
+    LBL_0:
+        IL_0022: ldc.i4 100
+        IL_0027: ret
+
+    LBL_4:
+        IL_0028: ldc.i4 500
+        IL_002d: ret
+
+    LBL_1:
+        IL_002e: ldc.i4 200
+        IL_0033: ret
+
+    LBL_2:
+        IL_0034: ldc.i4 300
+        IL_0039: ret
+
+    LBL_DEFAULT:
+        IL_003a: ldc.i4.m1
+        IL_003b: ret
+    }
+}

ICSharpCode.Decompiler/DecompilerSettings.cs

@@ -2375,6 +2375,26 @@ namespace ICSharpCode.Decompiler
 			}
 		}
 
+		bool sortSwitchSections = false;
+
+		/// <summary>
+		/// Sort switch sections by their label value instead of by IL offset.
+		/// Useful when diffing decompiler output across rebuilds of obfuscated assemblies,
+		/// where IL block layout is unstable but the case-to-value mapping is not.
+		/// </summary>
+		[Category("DecompilerSettings.Other")]
+		[Description("DecompilerSettings.SortSwitchSections")]
+		public bool SortSwitchSections {
+			get { return sortSwitchSections; }
+			set {
+				if (sortSwitchSections != value)
+				{
+					sortSwitchSections = value;
+					OnPropertyChanged();
+				}
+			}
+		}
+
 		bool checkForOverflowUnderflow = false;
 
 		/// <summary>

ICSharpCode.Decompiler/IL/ControlFlow/SwitchDetection.cs

@@ -208,7 +208,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 
 				controlFlowGraph = null; // control flow graph is no-longer valid
 				blockContainerNeedsCleanup = true;
-				SortSwitchSections(sw);
+				SortSwitchSections(sw, context);
 			}
 			else
 			{
@@ -249,10 +249,16 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 					return false;
 				});
 			AdjustLabels(sw, context);
-			SortSwitchSections(sw);
+			SortSwitchSections(sw, context);
 		}
 
-		static void SortSwitchSections(SwitchInstruction sw)
+		static void SortSwitchSections(SwitchInstruction sw, ILTransformContext context)
+		{
+			if (context.Settings.SortSwitchSections)
+			{
+				sw.Sections.ReplaceList(sw.Sections.OrderBy(s => s.Labels.Values.FirstOrDefault()));
+			}
+			else
 			{
 				sw.Sections.ReplaceList(sw.Sections.OrderBy(s => s.Body switch {
 					Branch b => b.TargetILOffset,
@@ -260,6 +266,7 @@ namespace ICSharpCode.Decompiler.IL.ControlFlow
 					_ => (int?)null
 				}).ThenBy(s => s.Labels.Values.FirstOrDefault()));
 			}
+		}
 
 		static void AdjustLabels(SwitchInstruction sw, ILTransformContext context)
 		{

ILSpy/Properties/Resources.Designer.cs

@@ -1424,6 +1424,15 @@ namespace ICSharpCode.ILSpy.Properties {
             }
         }
 
+        /// <summary>
+        ///   Looks up a localized string similar to Sort switch sections by case label value.
+        /// </summary>
+        public static string DecompilerSettings_SortSwitchSections {
+            get {
+                return ResourceManager.GetString("DecompilerSettings.SortSwitchSections", resourceCulture);
+            }
+        }
+
         /// <summary>
         ///   Looks up a localized string similar to Detect switch on integer even if IL code does not use a jump table.
         /// </summary>

ILSpy/Properties/Resources.resx

@@ -504,6 +504,9 @@ Are you sure you want to continue?</value>
   <data name="DecompilerSettings.SortCustomAttributes" xml:space="preserve">
     <value>Sort custom attributes</value>
   </data>
+  <data name="DecompilerSettings.SortSwitchSections" xml:space="preserve">
+    <value>Sort switch sections by case label value</value>
+  </data>
   <data name="DecompilerSettings.SparseIntegerSwitch" xml:space="preserve">
     <value>Detect switch on integer even if IL code does not use a jump table</value>
   </data>