Dispatch declaration overrides in Experimental_ComponentOverrides

[Timothee Guerin (timotheeguerin)]

An override descriptor already accepted a declaration entry, but nothing ever dispatched to it — only reference was wired up. So an emitter could change how a type is referenced and had no say in how it is declared. The only way to customize a declaration was to copy the framework component into your own package and diverge from it, which is exactly what @typespec/http-server-csharp did for classes, properties and enums.

Experimental_OverridableComponent now dispatches declaration too, and the C# ClassDeclaration, Property and EnumDeclaration render through it. An override can replace the declaration outright, or re-render the default with different props:

const overrides = Experimental_ComponentOverridesConfig().forTypeKind("ModelProperty", {
  declaration: (props) =>
    isSecret(props.type) ? (
      <props.Declaration {...props.declarationProps} public={false} internal />
    ) : (
      props.default
    ),
});

props.Declaration is the unwrapped body, so re-rendering it does not recurse back through the override.

The declaration props type is generic and defaults to Record<string, any>, because the existing Experimental_CustomTypeToProps map is TypeScript-specific (VarDeclarationProps, ObjectPropertyProps) and means nothing for C#. Callers that want type safety pass the concrete props type: .forTypeKind<"ModelProperty", PropertyProps>(...).

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Independent — targets main and can merge on its own.

One of 7 PRs moving @typespec/http-server-csharp onto the emitter framework instead of its private forks: #11596, #11597, #11598, #11599, #11600, #11601, #11602.

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commit: b10f5fb

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• ✅ @typespec/emitter-framework

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@typespec/emitter-framework - feature ✏️

Support declaration overrides in Experimental_ComponentOverrides,> ,> Only reference overrides were dispatched, so an emitter could customize how a type is referenced but not how it is declared, forcing it to fork the framework's declaration components. The C# ClassDeclaration, Property and EnumDeclaration now render through the override point.,> ,> Override precedence is resolved per override kind, so a type-level override that only defines reference does not shadow a kind-level declaration override, and vice versa.,> ,> tsx,> const overrides = Experimental_ComponentOverridesConfig().forTypeKind("ModelProperty", {,> declaration: (props) =>,> props.type.name === "id" ? (,> <props.Declaration {...props.declarationProps} name="Identifier" />,> ) : (,> props.default,> ),,> });,>

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Pull request overview

This PR extends Experimental_ComponentOverrides so emitters can override declarations (not just references), and wires the C# declaration components (ClassDeclaration, Property, EnumDeclaration) through the overridable dispatch point. This unblocks customizing how types are declared without forking framework components, supporting the ongoing migration of @typespec/http-server-csharp onto the emitter framework.

Changes:

• Add declaration-override typing + dispatch support to Experimental_OverridableComponent and override config generics.
• Wrap C# ClassDeclaration, Property, and EnumDeclaration render paths with Experimental_OverridableComponent in declaration mode.
• Add C# tests covering declaration override behavior and add a Chronus changelog entry.

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Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

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File	Description
packages/emitter-framework/src/csharp/components/property/property.tsx	Routes property declarations through the overridable declaration dispatch.
packages/emitter-framework/src/csharp/components/enum/declaration.tsx	Routes enum declarations through the overridable declaration dispatch.
packages/emitter-framework/src/csharp/components/class/declaration.tsx	Routes class declarations through the overridable declaration dispatch.
packages/emitter-framework/src/csharp/components/class/declaration.test.tsx	Adds tests validating declaration overrides for class/property/enum declarations.
packages/emitter-framework/src/core/components/overrides/config.ts	Extends overrides config APIs to carry a generic declaration-props type parameter.
packages/emitter-framework/src/core/components/overrides/component-overrides.tsx	Adds declaration override types and dispatch logic to Experimental_OverridableComponent.
.chronus/changes/ef-declaration-overrides-2026-8-5.md	Changelog entry for declaration override support.

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Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated no new comments.