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[XSG] Fix OnPlatform to generate default values for missing platforms #32778

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Merged
StephaneDelcroix merged 9 commits into from
Nov 25, 2025
Merged

[XSG] Fix OnPlatform to generate default values for missing platforms #32778

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f1c462d
Initial plan
Copilot Nov 20, 2025
df2dbc4
Fix OnPlatform SourceGen to use default value instead of removing pro…
Copilot Nov 20, 2025
9f48d25
Add runtime test to verify OnPlatform default value behavior
Copilot Nov 20, 2025
1cadffd
Address PR review feedback - move runtime test to shared inflator test
Copilot Nov 20, 2025
facc2a1
Improve assertion
simonrozsival Nov 21, 2025
dee492a
Simplify test setup
simonrozsival Nov 21, 2025
a7be478
Fix test
simonrozsival Nov 21, 2025
ca683e0
Apply suggestions from code review
simonrozsival Nov 24, 2025
0f8ff25
Remove custom constructors in test
simonrozsival Nov 24, 2025
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22 changes: 20 additions & 2 deletions src/Controls/src/Xaml/SimplifyOnPlatformVisitor.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -86,6 +86,16 @@ public void Visit(ElementNode node, INode parentNode)
INode keyNode = null;
bool hasKey = node.Properties.TryGetValue(XmlName.xKey, out keyNode);

// If no value found for target platform and no Default,
// create a default value node if we have x:TypeArguments
if (onNode == null && node.XmlType.TypeArguments != null && node.XmlType.TypeArguments.Count > 0)
{
// Create default value for the type (to match OnPlatform<T> runtime behavior)
var typeArg = node.XmlType.TypeArguments[0];
var elementNode = new ElementNode(typeArg, typeArg.NamespaceUri, node.NamespaceResolver, node.LineNumber, node.LinePosition);
onNode = elementNode;
}

// If OnPlatform has x:Key but the replacement node is a ValueNode,
// check if we have x:TypeArguments to create a proper ElementNode
if (hasKey && onNode is ValueNode valueNode)
Expand Down Expand Up @@ -123,7 +133,11 @@ public void Visit(ElementNode node, INode parentNode)
parentEnode.Properties[name] = onNode;
}
else
parentEnode.Properties.Remove(name);
{
// No value and no x:TypeArguments - skip simplification
// This maintains consistency with runtime OnPlatform<T> behavior
return;
}
return;
}

Expand All @@ -141,7 +155,11 @@ public void Visit(ElementNode node, INode parentNode)
parentEnode2.CollectionItems[index] = onNode;
}
else
parentEnode2.CollectionItems.RemoveAt(index);
{
// No value and no x:TypeArguments - skip simplification
// This maintains consistency with runtime OnPlatform<T> behavior
return;
}
}
}
}
Expand Down
55 changes: 55 additions & 0 deletions src/Controls/tests/SourceGen.UnitTests/InitializeComponent/SimplifyOnPlatform.cs
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Expand Up @@ -352,4 +352,59 @@ public TestPage()
Assert.Contains("Red", generated, StringComparison.Ordinal);
Assert.DoesNotContain("Blue", generated, StringComparison.Ordinal);
}

[Fact]
public void OnPlatformWithMissingTargetPlatformShouldUseDefault()
{
// Reproduces Bugzilla39636: When MacCatalyst is not defined in OnPlatform,
// SourceGen should use default(T) instead of throwing an exception
var xaml =
"""
<?xml version="1.0" encoding="UTF-8"?>
<ContentPage
xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
x:Class="Test.TestPage">
<ContentPage.Resources>
<OnPlatform x:Key="SizeMedium" x:TypeArguments="x:Double">
<On Platform="iOS" Value="40"/>
<On Platform="Android" Value="30"/>
<On Platform="UWP" Value="60"/>
</OnPlatform>
</ContentPage.Resources>
<Label Text="Test" WidthRequest="{StaticResource SizeMedium}" />
</ContentPage>
""";

var code =
"""
using System;
using Microsoft.Maui.Controls;
using Microsoft.Maui.Controls.Xaml;

namespace Test;

[XamlProcessing(XamlInflator.SourceGen)]
public partial class TestPage : ContentPage
{
public TestPage()
{
InitializeComponent();
}
}
""";

// Test with MacCatalyst where platform is not defined
var (result, generated) = RunGenerator(xaml, code, targetFramework: "net10.0-maccatalyst");

// Should not have any errors (no TargetInvocationException)
Assert.False(result.Diagnostics.Any(d => d.Severity == Microsoft.CodeAnalysis.DiagnosticSeverity.Error));

// Should generate SetValue with default(double) for the WidthRequest property
// The generated code should look like: label.SetValue(global::Microsoft.Maui.Controls.VisualElement.WidthRequestProperty, double1);
// where double1 is assigned from double0 which is: double double0 = default;
Assert.Contains("double double0 = default;", generated, StringComparison.Ordinal);
Assert.Contains("var double1 = double0;", generated, StringComparison.Ordinal);
Assert.Contains("label.SetValue(global::Microsoft.Maui.Controls.VisualElement.WidthRequestProperty, double1);", generated, StringComparison.Ordinal);
}
}
14 changes: 14 additions & 0 deletions src/Controls/tests/Xaml.UnitTests/Issues/Bugzilla39636.xaml
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Original file line number Diff line number Diff line change
@@ -0,0 +1,14 @@
<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:local="clr-namespace:Microsoft.Maui.Controls.Xaml.UnitTests"
x:Class="Microsoft.Maui.Controls.Xaml.UnitTests.Bugzilla39636">
<ContentPage.Resources>
<OnPlatform x:Key="SizeMedium" x:TypeArguments="x:Double">
<On Platform="iOS" Value="40"/>
<On Platform="Android" Value="30"/>
<On Platform="UWP" Value="60"/>
</OnPlatform>
</ContentPage.Resources>
<Label x:Name="testLabel" Text="Test" WidthRequest="{StaticResource SizeMedium}" />
</ContentPage>
39 changes: 39 additions & 0 deletions src/Controls/tests/Xaml.UnitTests/Issues/Bugzilla39636.xaml.cs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,39 @@
using Microsoft.Maui.Controls.Core.UnitTests;
using Microsoft.Maui.Devices;
using NUnit.Framework;

namespace Microsoft.Maui.Controls.Xaml.UnitTests;

public partial class Bugzilla39636 : ContentPage
{
[TestFixture]
class Tests
{
MockDeviceInfo mockDeviceInfo;

[SetUp]
public void Setup()
{
Application.SetCurrentApplication(new MockApplication());
DeviceInfo.SetCurrent(mockDeviceInfo = new MockDeviceInfo());
}

[TearDown] public void TearDown() => DeviceInfo.SetCurrent(null);

[Test]
public void OnPlatformWithMissingTargetPlatformShouldUseDefault([Values] XamlInflator inflator)
{
// Reproduces Bugzilla39636: When MacCatalyst is not defined in OnPlatform,
// all inflators should use default(T) instead of throwing an exception

// Test with MacCatalyst where platform is not defined
mockDeviceInfo.Platform = DevicePlatform.MacCatalyst;
var page = new Bugzilla39636(inflator);

// Should use default value (0.0 for double) instead of throwing
Assert.That(page.testLabel, Is.Not.Null);
Assert.That(page.testLabel.WidthRequest, Is.EqualTo(0.0));
}
}
}

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