Handle custom external model bases by live1206 · Pull Request #11183 · microsoft/typespec

live1206 · 2026-07-07T06:40:43Z

Summary

Represent external model mappings with SystemObjectModelProvider so generated models can inherit from resolved framework or referenced C# types without emitting the external model itself.
Preserve model inheritance behavior across custom/external bases:
- propagate the resolved base type and interface metadata, including generic interface arguments;
- avoid regenerating members owned by the external type;
- control whether external-base constructor parameters flow into derived constructors.
Improve model reader/writer serialization for custom and external base hierarchies:
- centralize MRW interface detection, provider resolution, hierarchy traversal, and overridability checks in shared internal helpers;
- resolve mapped and referenced type providers when method metadata is available;
- conservatively avoid overrides when an external type cannot be resolved.
Tighten XML serialization override detection so XmlModelWriteCore only overrides a compatible, accessible, overridable base method:
- retain XML-specific signature and internal-only accessibility validation;
- account for customized generated bases and method replacement;
- reject JSON-only, wrong-signature, non-virtual, protected/public, sealed, and shadowed ancestor methods.
Keep MRW create-core return types rooted at the meaningful custom base type and only participate in override chains supported by that base.
Keep management-plane wire-path deduplication out of MTG; downstream generators remain responsible for management-specific attributes and behavior.

Validation

npm run build
npm run format
npm run cop
dotnet test ./generator/Microsoft.TypeSpec.Generator/test/Microsoft.TypeSpec.Generator.Tests.csproj --no-restore
dotnet test ./generator/Microsoft.TypeSpec.Generator.ClientModel/test/Microsoft.TypeSpec.Generator.ClientModel.Tests.csproj --no-restore
Azure SDK for .NET management generator validation: no regeneration diff.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

pkg-pr-new · 2026-07-07T06:42:50Z

npm i https://pkg.pr.new/@typespec/http-client-csharp@11183

commit: 0ba934f

github-actions · 2026-07-07T06:43:41Z

No changes needing a change description found.

Use the system object model provider's base model chain for inheritance and expose customization-only properties through a TypeProvider hook instead of storing inherited properties separately. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Populate synthetic system object input models with referenced type properties so existing ModelProvider inheritance handles inherited property filtering. Skip constructor forwarding for synthetic custom-base providers so external constructor surfaces are not generated into derived models. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Cover canonical generated duplicate removal when a custom system object base exposes the same wire path through a differently named property. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Stop storing a base model provider on SystemObjectModelProvider. Seed the CSharpTypeMap for external base types and let the existing BaseType/BuildBaseModelProvider path resolve inheritance normally. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Remove the ModelProvider-local custom base helper and centralize synthetic SystemObjectModelProvider creation in TypeFactory. ModelProvider now only asks TypeFactory to create/register a model provider for a custom external base, then uses the existing BaseType/CSharpTypeMap lookup path for inheritance. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

The root cause is fixed in microsoft/typespec#11183, so this SDK PR should not carry generator changes. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

This reverts commit 6f3c763.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

This PR refines how the C# generator models and serializes types that derive from custom/external base classes, removing reliance on a synthetic base-provider path and instead using existing type metadata and hierarchy-aware detection (especially for MRW XML serialization). It also adds test coverage around external base chains and canonical wire-path deduplication.

Changes:

Extend model/provider plumbing to better represent external/custom base type chains (base type + constructor-parameter propagation behavior).
Improve MRW serialization override decisions (JSON root return type discovery; XML override detection with signature/accessibility/overridability checks).
Add tests + test data for external base behaviors and canonical duplicate wire-path filtering.

Reviewed changes

Copilot reviewed 19 out of 19 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/test/Providers/SystemObjectModelProviderTests.cs	Adds coverage for representing an external base chain via type metadata without duplicating inherited properties.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/test/Providers/ModelProviders/TestData/ModelCustomizationTests/CanFilterCanonicalDuplicateWirePathFromSystemObjectModelProviderBase/MockInputModel.cs	Adds test customization source defining a framework-like base (`ResourceData`) and a derived partial model.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/test/Providers/ModelProviders/ModelCustomizationTests.cs	Adds test ensuring canonical duplicate wire-path properties are filtered when a system/custom base already maps that wire path.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/src/Writers/CodeWriter.cs	Adds `sealed` emission support for method/property signatures.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/src/Providers/TypeProvider.cs	Enhances customized-member filtering to consider canonical duplicate wire paths (not just names).
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/src/Providers/SystemObjectModelProvider.cs	Adds base-type propagation and derived-constructor parameter behavior control for wrapped system types.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/src/Providers/NamedTypeSymbolProvider.cs	Adds interface list materialization and propagates `sealed` into method signature modifiers.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/src/Providers/ModelProvider.cs	Gates base-constructor parameter propagation based on the base provider’s preference.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/src/Primitives/MethodSignatureModifiers.cs	Adds `Sealed` to the modifier bitflags.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/XmlSerializationCustomizationTests.cs	Adds extensive XML override-detection tests across multiple base scenarios.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/XmlSerializationCustomizationTests/XmlModelWriteCoreOverridesGeneratedBaseWithCustomReplacement/BaseModel.cs	Adds test data for a generated base with a compatible virtual XML core method.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/XmlSerializationCustomizationTests/XmlModelWriteCoreDoesNotOverrideProtectedCustomExternalBase/MockInputModel.cs	Adds test data for a protected XML base method that must not be overridden by an internal method.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/XmlSerializationCustomizationTests/XmlModelWriteCoreDoesNotOverrideJsonOnlyCustomBase/MockInputModel.cs	Adds test data for a JSON-only base to ensure XML methods are not overridden incorrectly.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/XmlSerializationCustomizationTests/XmlModelWriteCoreDoesNotOverrideGeneratedBaseWithSealedCustomMethod/BaseModel.cs	Adds test data ensuring a sealed override in a customized base prevents derived overrides.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/XmlSerializationCustomizationTests/XmlModelWriteCoreDoesNotOverrideGeneratedBaseWithProtectedCustomMethod/BaseModel.cs	Adds test data ensuring protected custom methods don’t trigger internal overrides.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/TestData/XmlSerializationCustomizationTests/XmlModelWriteCoreDoesNotOverrideGeneratedBaseWithNonVirtualCustomMethod/BaseModel.cs	Adds test data ensuring non-virtual methods don’t trigger overrides.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/test/Providers/MrwSerializationTypeDefinitions/SystemObjectModelSerializationTests.cs	Adjusts system-base MRW tests to explicitly model interface implementation via a specialized provider.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/src/Providers/MrwSerializationTypeDefinition.Xml.cs	Reworks XML override detection to be XML-specific and hierarchy-aware.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator.ClientModel/src/Providers/MrwSerializationTypeDefinition.cs	Improves MRW override decisions and root-type discovery for models with custom/external bases.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 81a9ead3-77ac-498f-ae8f-d9f4e69ce052

jorgerangel-msft

Can you share the regen preview please?

Copilot

Pull request overview

Copilot reviewed 21 out of 21 changed files in this pull request and generated 1 comment.

…tom-base-mrw

- Fix WriteProperty emitting 'protected private' instead of 'private protected' - Replace null-forgiving BaseType access with an explicit null check - Rename TryGet* helpers that return nullable to Get* - Narrow ShouldUseFullConstructorInDerivedTypes to private protected - Reuse TestTypeProvider for the inherited-interface test Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 81a9ead3-77ac-498f-ae8f-d9f4e69ce052

… those methods A hand-authored base class was unconditionally used as the return type of the generated JsonModelCreateCore/PersistableModelCreateCore methods. When such a base does not take part in MRW serialization (for example Azure.AI.VoiceLive's VoiceProvider, a plain abstract grouping class), the generated base declared a wider return type than its derived overrides. That produces covariant returns, which fail to compile on netstandard2.0 with CS8830, and changes the signature of protected virtual members that are part of the shipped public API. Defer to the custom base only when it actually declares the *Core creation methods, in which case the signatures must match for the override to be valid. This also removes two unreachable fallbacks and the now unused GetRootBaseType/IsFrameworkRootType helpers. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 38fbad13-07b0-42dd-ae90-b5243c7b1d85

@typespec/http-client-csharp is excluded from the pnpm workspace, so chronus rejects change entries that reference it. The emitter package does not use chronus for changelogs. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 38fbad13-07b0-42dd-ae90-b5243c7b1d85

azure-sdk-automation · 2026-07-28T07:22:57Z

You can try these changes here

🛝 Playground	🌐 Website	🛝 VSCode Extension

A custom base was previously matched on method name alone, so a base whose JsonModelWriteCore is non-virtual, sealed, not protected, or declared with a different signature still caused the generated method to be emitted as `override`, producing CS0506/CS0115/CS0507. Mirror the validation the XML path performs: exact signature, protected accessibility, and overridability. Also fix InterfaceTests order dependency by initializing the mock generator in [SetUp] so the tests pass in isolation. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 38fbad13-07b0-42dd-ae90-b5243c7b1d85

live1206 · 2026-07-28T09:34:30Z

Can you share the regen preview please?

latest regen: Azure/azure-sdk-for-net#61461

GetCustomMrwBaseRootType delegated to GetCustomBaseMethodReturnType, which in turn delegated to GetMethodReturnTypeInHierarchy; each had exactly one caller. Inline the chain into a single method. Also restore the ShouldSkipDerivedSerializationMethodOverrides doc comment, which was left attached to GetCustomSerializationBaseType. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 38fbad13-07b0-42dd-ae90-b5243c7b1d85

Handle custom external model bases

bd4a53f

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

microsoft-github-policy-service Bot added the emitter:client:csharp Issue for the C# client emitter: @typespec/http-client-csharp label Jul 7, 2026

live1206 mentioned this pull request Jul 7, 2026

Fix mgmt custom base duplicate wire properties Azure/azure-sdk-for-net#60685

Closed

live1206 and others added 6 commits July 7, 2026 06:54

Add wire path duplicate filtering test

cb4ab51

Cover canonical generated duplicate removal when a custom system object base exposes the same wire path through a differently named property. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Use base type providers for custom base serialization

929133e

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

live1206 and others added 11 commits July 7, 2026 09:44

Keep base hierarchy helpers internal

6f3c763

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Revert "Keep base hierarchy helpers internal"

41b0d05

This reverts commit 6f3c763.

Avoid public TypeProvider helper APIs

b7815f6

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

fix(http-client-csharp): use xml-specific serialization override check

801b710

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

fix(http-client-csharp): detect customized xml base serialization

7344f89

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

fix(http-client-csharp): validate custom xml core override signature

b64a332

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

fix(http-client-csharp): require internal custom xml core overrides

d48bfd9

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

fix(http-client-csharp): validate external xml core overrides

92343e0

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

fix(http-client-csharp): ignore reflected external xml core hooks

7606827

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

fix(http-client-csharp): reject sealed xml core overrides

9434c3a

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

fix(http-client-csharp): stop xml core lookup at incompatible overrides

15757c7

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

live1206 marked this pull request as ready for review July 8, 2026 07:01

live1206 requested review from JoshLove-msft, ShivangiReja, jorgerangel-msft, joseharriaga, jsquire and m-nash as code owners July 8, 2026 07:01

Copilot AI reviewed Jul 9, 2026

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jorgerangel-msft reviewed Jul 9, 2026

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live1206 and others added 2 commits July 10, 2026 01:25

Fix custom base review feedback

6e556ff

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Avoid exposing base type provider

8169c69

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

jorgerangel-msft reviewed Jul 10, 2026

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live1206 added 3 commits July 27, 2026 07:40

Merge origin/main into fix/system-object-custom-base-mrw

5738549

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 81a9ead3-77ac-498f-ae8f-d9f4e69ce052

test(http-client-csharp): align delayed XML base coverage

eee4d55

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 81a9ead3-77ac-498f-ae8f-d9f4e69ce052

fix(http-client-csharp): address custom base review feedback

523b60f

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 81a9ead3-77ac-498f-ae8f-d9f4e69ce052

jorgerangel-msft reviewed Jul 27, 2026

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jorgerangel-msft requested a review from Copilot July 27, 2026 17:05

Copilot started reviewing on behalf of jorgerangel-msft July 27, 2026 17:06 View session

Copilot AI reviewed Jul 27, 2026

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Comment thread packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/src/Writers/CodeWriter.cs

live1206 and others added 2 commits July 28, 2026 02:49

Merge remote-tracking branch 'origin/main' into fix/system-object-cus…

a0d58fe

…tom-base-mrw

JoshLove-msft reviewed Jul 28, 2026

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Comment thread ...tor/Microsoft.TypeSpec.Generator.ClientModel/src/Providers/MrwSerializationTypeDefinition.cs Outdated

JoshLove-msft reviewed Jul 28, 2026

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Comment thread ...rator/Microsoft.TypeSpec.Generator/test/Providers/NamedTypeSymbolProviders/InterfaceTests.cs

live1206 and others added 2 commits July 28, 2026 07:09

jorgerangel-msft approved these changes Jul 28, 2026

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Comment thread ...tor/Microsoft.TypeSpec.Generator.ClientModel/src/Providers/MrwSerializationTypeDefinition.cs

JoshLove-msft approved these changes Jul 29, 2026

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live1206 enabled auto-merge July 29, 2026 02:00

live1206 added this pull request to the merge queue Jul 29, 2026

Merged via the queue into microsoft:main with commit d320a53 Jul 29, 2026
29 checks passed

live1206 deleted the fix/system-object-custom-base-mrw branch July 29, 2026 02:45

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