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Unify C# model base type provider resolution #11262

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905d80a
refactor(http-client-csharp): unify base type provider resolution
live1206 Jul 15, 2026
5b41ad0
refactor(http-client-csharp): make base provider resolution private
live1206 Jul 15, 2026
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4 changes: 2 additions & 2 deletions ...nerator.ClientModel/test/Providers/Definitions/ModelReaderWriterContextDefinitionTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1183,7 +1183,7 @@ public DuplicateDerivedProvider(InputModelType inputModelType, ModelProvider bas
_baseProvider = baseProvider;
}

protected override ModelProvider? BuildBaseModelProvider() => _baseProvider;
internal override TypeProvider? BaseTypeProvider => _baseProvider;

protected override string BuildName() => "DerivedModel";
}
Expand All @@ -1196,7 +1196,7 @@ public CyclicBaseProvider(InputModelType inputModelType, bool includeFrameworkPr

public ModelProvider? BaseProvider { get; set; }

protected override ModelProvider? BuildBaseModelProvider() => BaseProvider;
internal override TypeProvider? BaseTypeProvider => BaseProvider;
}

public class FrameworkTypeImplementingOtherFrameworkType : ComplexFrameworkType
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5 changes: 4 additions & 1 deletion ...tor.ClientModel/test/Providers/MrwSerializationTypeDefinitions/ModelCustomizationTests.cs
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Expand Up @@ -320,7 +320,10 @@ public async Task CanCustomizeBaseType(bool declareBaseTypeInCustomCode, bool ca
inputModels: () => [inputModel, baseModel],
compilation: async () => await Helpers.GetCompilationFromDirectoryAsync(declareBaseTypeInCustomCode.ToString()));

var modelProvider = mockGenerator.Object.OutputLibrary.TypeProviders.Single(t => t.Name == "MockInputModel");
var modelProvider = (ModelProvider)mockGenerator.Object.OutputLibrary.TypeProviders.Single(t => t.Name == "MockInputModel");

Assert.IsNotNull(modelProvider.BaseTypeProvider);
Assert.AreSame(modelProvider.BaseModelProvider, modelProvider.BaseTypeProvider);

// should not have the additionalProperties dictionary
Assert.AreEqual(0, modelProvider.Fields.Count);
Expand Down
6 changes: 2 additions & 4 deletions ...del/test/Providers/MrwSerializationTypeDefinitions/SystemObjectModelSerializationTests.cs
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Expand Up @@ -16,9 +16,7 @@ namespace Microsoft.TypeSpec.Generator.ClientModel.Tests.Providers.MrwSerializat
{
/// <summary>
/// Tests that serialization methods use correct modifiers when a model's base is
/// <see cref="SystemObjectModelProvider"/>. This validates behavior that would be
/// impossible with <see cref="SystemObjectTypeProvider"/> (which cannot serve as
/// <see cref="ModelProvider.BaseModelProvider"/>).
/// <see cref="SystemObjectModelProvider"/>.
/// </summary>
internal class SystemObjectModelSerializationTests
{
Expand Down Expand Up @@ -358,7 +356,7 @@ private class DelayedBaseModelProvider(InputModelType inputModel) : ModelProvide
{
public ModelProvider? BaseModel { get; set; }

protected override ModelProvider? BuildBaseModelProvider() => BaseModel;
internal override TypeProvider? BaseTypeProvider => BaseModel;

protected override CSharpType? BuildBaseType() => BaseModel?.Type;
}
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120 changes: 54 additions & 66 deletions .../http-client-csharp/generator/Microsoft.TypeSpec.Generator/src/Providers/ModelProvider.cs
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Expand Up @@ -62,7 +62,6 @@ protected override FormattableString BuildDescription()
private bool _buildingRawDataField;
private List<FieldProvider>? _additionalPropertyFields;
private List<PropertyProvider>? _additionalPropertyProperties;
private ModelProvider? _baseModelProvider;
private ConstructorProvider? _fullConstructor;
internal PropertyProvider? DiscriminatorProperty { get; private set; }
private ValueExpression DiscriminatorLiteral => Literal(_inputModel.DiscriminatorValue ?? "");
Expand Down Expand Up @@ -124,57 +123,77 @@ private IReadOnlyList<ModelProvider> BuildDerivedModels()

return [.. derivedModels];
}
internal override TypeProvider? BaseTypeProvider => _baseTypeProvider ??= BuildBaseTypeProvider();
internal override TypeProvider? BaseTypeProvider => _baseTypeProvider ??= ResolveBaseTypeProvider();
private TypeProvider? _baseTypeProvider;

private TypeProvider? BuildBaseTypeProvider()
private TypeProvider? ResolveBaseTypeProvider()
{
// First check if there's a generated base model
if (BaseModelProvider != null)
var baseType = BaseType;
if (baseType is null)
{
return null;
}

var hasExistingProvider = CodeModelGenerator.Instance.TypeFactory.CSharpTypeMap.TryGetValue(baseType, out var existingProvider);
if (existingProvider is ModelProvider)
{
return BaseModelProvider;
return existingProvider;
}

// If there's a custom base type that's not a generated model, create a provider for it
if (CustomCodeView?.BaseType != null && !string.IsNullOrEmpty(CustomCodeView.BaseType.Namespace))
if (CustomCodeView?.BaseType is null)
{
var baseType = CustomCodeView.BaseType;
return existingProvider;
}

// Try to find it in the CSharpTypeMap first
if (CodeModelGenerator.Instance.TypeFactory.CSharpTypeMap.TryGetValue(baseType, out var existingProvider))
// Prefer a mapped model over a symbol provider for a custom base that names a generated model.
var matchingModel = CodeModelGenerator.Instance.TypeFactory.CSharpTypeMap
.FirstOrDefault(entry =>
entry.Value is ModelProvider &&
entry.Key.Name == baseType.Name &&
entry.Key.Namespace == baseType.Namespace)
.Value;
if (matchingModel is null)
{
// Ensure visitor-renamed input models have been registered before falling back to a symbol provider.
foreach (var model in CodeModelGenerator.Instance.InputLibrary.InputNamespace.Models)
{
return existingProvider;
CodeModelGenerator.Instance.TypeFactory.CreateModel(model);
}

// Try to find the type in the customization compilation. Referenced assemblies are
// included so custom bases from framework or external packages are represented by
// normal symbol-backed providers.
var baseTypeProvider = CodeModelGenerator.Instance.SourceInputModel.FindForTypeInCustomization(
baseType.Namespace,
baseType.Name,
baseType.DeclaringType?.Name,
includeReferencedAssemblies: true);
matchingModel = CodeModelGenerator.Instance.TypeFactory.CSharpTypeMap
.FirstOrDefault(entry =>
entry.Value is ModelProvider &&
entry.Key.Name == baseType.Name &&
entry.Key.Namespace == baseType.Namespace)
.Value;
}

if (matchingModel is not null)
{
CodeModelGenerator.Instance.TypeFactory.CSharpTypeMap[baseType] = matchingModel;
return matchingModel;
}

if (baseTypeProvider != null)
{
// Cache it in CSharpTypeMap for future lookups
CodeModelGenerator.Instance.TypeFactory.CSharpTypeMap[baseType] = baseTypeProvider;
return baseTypeProvider;
}
if (hasExistingProvider || string.IsNullOrEmpty(baseType.Namespace))
{
return existingProvider;
}

var matchingProvider = CodeModelGenerator.Instance.SourceInputModel.FindForTypeInCustomization(
baseType.Namespace,
baseType.Name,
baseType.DeclaringType?.Name,
includeReferencedAssemblies: true);

// If we couldn't find the type symbol, create a SystemObjectTypeProvider that
// represents the external type without member metadata.
var systemObjectTypeProvider = new SystemObjectTypeProvider(baseType);
// Cache it in CSharpTypeMap for future lookups
CodeModelGenerator.Instance.TypeFactory.CSharpTypeMap[baseType] = systemObjectTypeProvider;
return systemObjectTypeProvider;
if (matchingProvider is not null)
{
CodeModelGenerator.Instance.TypeFactory.CSharpTypeMap[baseType] = matchingProvider;
}

return null;
return matchingProvider;
}

public ModelProvider? BaseModelProvider
=> _baseModelProvider ??= BuildBaseModelProvider();
public ModelProvider? BaseModelProvider => BaseTypeProvider as ModelProvider;

/// <inheritdoc/>
public override void Reset()
Expand Down Expand Up @@ -384,37 +403,6 @@ private static bool IsDiscriminator(InputProperty property)
return property is InputModelProperty modelProperty && modelProperty.IsDiscriminator;
}

protected virtual ModelProvider? BuildBaseModelProvider()
{
var baseType = BaseType;
if (baseType is null)
{
return null;
}

if (CodeModelGenerator.Instance.TypeFactory.CSharpTypeMap.TryGetValue(baseType, out var provider)
&& provider is ModelProvider modelProvider)
{
return modelProvider;
}

if (CustomCodeView?.BaseType != null && !string.IsNullOrEmpty(baseType.Namespace))
{
foreach (var (mapKey, mapValue) in CodeModelGenerator.Instance.TypeFactory.CSharpTypeMap)
{
if (mapValue is ModelProvider model
&& mapKey.Name == baseType.Name
&& mapKey.Namespace == baseType.Namespace)
{
CodeModelGenerator.Instance.TypeFactory.CSharpTypeMap[baseType] = model;
return model;
}
}
}

return null;
}

private List<FieldProvider> BuildAdditionalPropertyFields()
{
var fields = new List<FieldProvider>();
Expand Down
3 changes: 1 addition & 2 deletions ...-csharp/generator/Microsoft.TypeSpec.Generator/src/Providers/SystemObjectModelProvider.cs
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Expand Up @@ -9,8 +9,7 @@ namespace Microsoft.TypeSpec.Generator.Providers
{
/// <summary>
/// Represents a model type from an external assembly (system or referenced assembly) that is mapped
/// from an input model type. Unlike <see cref="SystemObjectTypeProvider"/> which extends <see cref="TypeProvider"/>,
/// this class extends <see cref="ModelProvider"/> so it can serve as a <see cref="ModelProvider.BaseModelProvider"/>
/// from an input model type. This class can serve as a <see cref="ModelProvider.BaseModelProvider"/>
/// for derived models that inherit from system types.
/// <para>
/// This is used when a code generator maps an input model (e.g., an ARM Resource type) to an existing
Expand Down
61 changes: 0 additions & 61 deletions ...t-csharp/generator/Microsoft.TypeSpec.Generator/src/Providers/SystemObjectTypeProvider.cs
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This file was deleted.

2 changes: 1 addition & 1 deletion packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/src/TypeFactory.cs
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Expand Up @@ -180,7 +180,7 @@ protected internal TypeFactory()
}

// Add sentinel before construction to prevent re-entrant creation of the same model
// (e.g., when BuildBaseModelProvider triggers CreateModel for all input models).
// (e.g., when base type resolution triggers CreateModel for all input models).
InputTypeToModelProvider[model] = null;

// A model marked as external maps to a type that already exists in a framework or
Expand Down
3 changes: 2 additions & 1 deletion ...enerator/Microsoft.TypeSpec.Generator/test/Providers/ModelProviders/ModelProviderTests.cs
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Expand Up @@ -503,6 +503,7 @@ public void OverridingBuildBaseType_AutoResolvesBaseModelProviderToNullForNonMod

Assert.IsNotNull(actualDerived);
Assert.AreEqual(nonModelTypeProvider.Type, actualDerived!.BaseType);
Assert.AreSame(nonModelTypeProvider, actualDerived.BaseTypeProvider);
Assert.IsNull(actualDerived.BaseModelProvider);
}

Expand Down Expand Up @@ -565,7 +566,7 @@ public CyclicBaseModelProvider(InputModelType inputModel) : base(inputModel)

public ModelProvider? CyclicBase { get; set; }

protected override ModelProvider? BuildBaseModelProvider() => CyclicBase;
internal override TypeProvider? BaseTypeProvider => CyclicBase;
}

[Test]
Expand Down
23 changes: 2 additions & 21 deletions ...p/generator/Microsoft.TypeSpec.Generator/test/Providers/SystemObjectModelProviderTests.cs
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Expand Up @@ -13,15 +13,9 @@
namespace Microsoft.TypeSpec.Generator.Tests.Providers
{
/// <summary>
/// Tests for <see cref="SystemObjectModelProvider"/> that demonstrate capabilities
/// missing from the existing <see cref="SystemObjectTypeProvider"/>.
/// <para>
/// <see cref="SystemObjectTypeProvider"/> extends <see cref="TypeProvider"/> and cannot
/// serve as a <see cref="ModelProvider.BaseModelProvider"/>. <see cref="SystemObjectModelProvider"/>
/// extends <see cref="ModelProvider"/> to fill this gap — enabling derived models to inherit
/// Tests for <see cref="SystemObjectModelProvider"/>, which enables derived models to inherit
/// from framework/system types while getting proper property deduplication, raw data field, and
/// serialization handling.
/// </para>
/// </summary>
public class SystemObjectModelProviderTests
{
Expand Down Expand Up @@ -53,19 +47,8 @@ public void SystemObjectModelProvider_IsModelProvider()
Assert.IsInstanceOf<ModelProvider>(provider);
}

[Test]
public void SystemObjectTypeProvider_IsNotModelProvider()
{
var systemType = CreateSystemCSharpType("ResourceData", "TestFramework");
var provider = new SystemObjectTypeProvider(systemType);

Assert.IsNotInstanceOf<ModelProvider>(provider);
Assert.IsInstanceOf<TypeProvider>(provider);
}

// -------------------------------------------------------------------
// 2. Can serve as BaseModelProvider for derived models
// (SystemObjectTypeProvider cannot because it's not a ModelProvider)
// -------------------------------------------------------------------

[Test]
Expand Down Expand Up @@ -93,7 +76,6 @@ public void CanServeAsBaseModelProvider()
var derivedProvider = CodeModelGenerator.Instance.TypeFactory.CreateModel(derivedInputModel) as ModelProvider;
Assert.IsNotNull(derivedProvider);

// The base should be a SystemObjectModelProvider — impossible with SystemObjectTypeProvider
Assert.IsNotNull(derivedProvider!.BaseModelProvider);
Assert.IsInstanceOf<SystemObjectModelProvider>(derivedProvider.BaseModelProvider);
}
Expand Down Expand Up @@ -385,8 +367,7 @@ public void Constructor_ThrowsOnNullSystemType()

// -------------------------------------------------------------------
// 9. A derived discriminated model forwards its discriminator value to a
// SystemObjectModelProvider base constructor. This is impossible with
// SystemObjectTypeProvider because it cannot serve as a BaseModelProvider.
// SystemObjectModelProvider base constructor.
// -------------------------------------------------------------------

[Test]
Expand Down
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