Fix #592

Author: mingyaulee

XmlSchemaClassGenerator.Tests/XmlTests.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.CodeDom;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
@@ -2269,6 +2269,85 @@ public void DoNotGenerateSamePropertiesInDerivedInterfacesClassTest()
 
     }
 
+    [Fact]
+    public void ChoiceWithDuplicateElementsInSequencesEmitsCorrectOrder()
+    {
+        const string xsd = 
+            """
+            <?xml version="1.0" encoding="UTF-8"?>
+            <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
+                elementFormDefault="qualified" attributeFormDefault="unqualified">
+
+                <xs:element name="Root">
+                    <xs:complexType>
+                        <xs:choice>
+                            <xs:sequence>
+                                <xs:element name="FirstChoiceElement1" type="xs:string"/>
+                                <xs:element name="FirstChoiceElement2" type="xs:string"/>
+                                <xs:element name="SharedElement1" type="xs:string"/>
+                                <xs:element name="FirstChoiceElement3" type="xs:string"/>
+                                <xs:element name="FirstChoiceElement4" type="xs:string"/>
+                                <xs:element name="SharedElement2" type="xs:string"/>
+                                <xs:element name="FirstChoiceElement5" type="xs:string"/>
+                                <xs:element name="FirstChoiceElement6" type="xs:string"/>
+                            </xs:sequence>
+                            <xs:sequence>
+                                <xs:element name="SecondChoiceElement1" type="xs:string"/>
+                                <xs:element name="SharedElement1" type="xs:string"/>
+                                <xs:element name="SecondChoiceElement2" type="xs:string"/>
+                                <xs:element name="SharedElement2" type="xs:string"/>
+                                <xs:element name="SecondChoiceElement3" type="xs:string"/>
+                            </xs:sequence>
+                        </xs:choice>
+                    </xs:complexType>
+                </xs:element>
+
+            </xs:schema>
+            """;
+        string[] expectedPropertiesInOrder =
+        [
+            "FirstChoiceElement1",
+            "FirstChoiceElement2",
+            "SecondChoiceElement1",
+            "SharedElement1",
+            "FirstChoiceElement3",
+            "FirstChoiceElement4",
+            "SecondChoiceElement2",
+            "SharedElement2",
+            "FirstChoiceElement5",
+            "FirstChoiceElement6",
+            "SecondChoiceElement3",
+        ];
+        var writer = new MemoryOutputWriter();
+        var gen = new Generator
+        {
+            OutputWriter = writer,
+            NamespaceProvider = new NamespaceProvider
+            {
+                GenerateNamespace = key => "Test"
+            },
+            AssemblyVisible = true,
+            EmitOrder = true,
+            // xs:choice branches sharing the same xs:element name violate UPA (Unique Particle Attribution),
+            EnableUpaCheck = false
+        };
+        gen.Generate([new StringReader(xsd)]);
+
+        var content = Assert.Single(writer.Content);
+
+        var assembly = Compiler.Compile(nameof(ChoiceWithDuplicateElementsInSequencesEmitsCorrectOrder), content);
+
+        var rootType = assembly.GetType("Test.Root");
+        Assert.NotNull(rootType);
+
+        var actualPropertiesInOrder = rootType.GetProperties()
+            .Where(property => Attribute.IsDefined(property, typeof(XmlElementAttribute)))
+            .OrderBy(property => property.GetCustomAttribute<XmlElementAttribute>().Order)
+            .Select(property => property.Name)
+            .ToArray();
+        Assert.Equal(expectedPropertiesInOrder, actualPropertiesInOrder);
+    }
+
     [Fact]
     public void NillableWithDefaultValueTest()
     {

XmlSchemaClassGenerator/ModelBuilder.cs

@@ -985,9 +985,22 @@ private IEnumerable<PropertyModel> CreatePropertiesForElements(Uri source, TypeM
         Substitute substitute = null, int order = 0, bool passProperties = true)
     {
         var properties = new List<PropertyModel>();
+        var initialOrder = order;
+        XmlSchemaObject prevParent = null;
+        int batchStart = -1;
 
         foreach (var item in items)
         {
+            // Track parent changes to detect transitions between choice branches.
+            // When elements from a new branch are encountered, batchStart marks where
+            // the new branch's properties begin in the list.
+            if (item.XmlParent != prevParent)
+            {
+                if (prevParent != null)
+                    batchStart = properties.Count;
+                prevParent = item.XmlParent;
+            }
+
             PropertyModel property = null;
 
             switch (item.XmlParticle)
@@ -1023,20 +1036,44 @@ private IEnumerable<PropertyModel> CreatePropertiesForElements(Uri source, TypeM
             // Discard duplicate property names. This is most likely due to:
             // - Choice or
             // - Element and attribute with the same name
-            if (property != null && !properties.Exists(p => p.Name == property.Name))
+            if (property != null)
             {
-                var itemDocs = GetDocumentation(item.XmlParticle);
-                property.Documentation.AddRange(itemDocs);
-
-                if (_configuration.EmitOrder)
-                    property.Order = order++;
+                var existingIndex = properties.FindIndex(p => p.Name == property.Name);
+                if (existingIndex >= 0)
+                {
+                    // Duplicate found in a choice branch - move the current batch of
+                    // new-branch properties to just before the duplicate's position
+                    // so that the interleaved order across branches is preserved.
+                    if (batchStart >= 0 && batchStart < properties.Count)
+                    {
+                        var count = properties.Count - batchStart;
+                        var segment = properties.GetRange(batchStart, count);
+                        properties.RemoveRange(batchStart, count);
+                        var adjustedIndex = existingIndex >= batchStart ? existingIndex - count : existingIndex;
+                        properties.InsertRange(adjustedIndex, segment);
+                    }
+                    batchStart = properties.Count;
+                }
+                else
+                {
+                    var itemDocs = GetDocumentation(item.XmlParticle);
+                    property.Documentation.AddRange(itemDocs);
 
-                property.IsDeprecated = itemDocs.Exists(d => d.Text.StartsWith("DEPRECATED"));
+                    property.IsDeprecated = itemDocs.Exists(d => d.Text.StartsWith("DEPRECATED"));
 
-                properties.Add(property);
+                    properties.Add(property);
+                }
             }
         }
 
+        // Reassign Order values based on final property positions,
+        // accounting for any reordering due to choice branch interleaving.
+        if (_configuration.EmitOrder)
+        {
+            for (var i = 0; i < properties.Count; i++)
+                properties[i].Order = initialOrder + i;
+        }
+
         return properties;
     }