Efv2 to main (microsoft#5996)

# Efv2 Integration  

This PR introduces the work on **Emitter Framework v2** from the feature
branch into main. The existing emitter framework functionality remains
unchanged for now, the new framework is added as a new package
@typespec/emitter-framework

### **Core Changes**  

- **Compiler Alloy Support**  
- The compiler now detects if `$onEmit` returns an **Alloy component**.
If so, it loads Alloy and calls `render`.
  - This enables emitters to use Alloy components.  

- **New Package: `@typespec/emitter-framework`**  
- Wraps raw Alloy components to accept **TypeSpec types as props** and
automatically generate language elements.
- Currently includes a **subexport for TypeScript (`/typescript`)**,
with plans to extend support to other languages.
- Example: `ts.Interface` can take a `Model` or `Interface` and directly
render a TypeScript interface with model properties or operation
signatures.

- **New Package: `@typespec/http-client`**  
- Provides **TypeKits** for querying the **type graph** in the context
of an **HTTP client**.
- The goal is to eventually **power TCGC** and host decorators that make
sense in this context.
- Remains **decoupled from Azure**, but we may later introduce an
extension package (`@azure-tools/http-client-azure`) for Azure-specific
logic and decorators.

###  **Follow Up Work**  
- Deprecate EFv1
- A follow up API review and clean-up will be needed, specifically
around TypeKits

.chronus/changes/joheredi-efv2-main-2025-1-13-1-49-16.md

@@ -0,0 +1,11 @@
+---
+changeKind: feature
+packages:
+  - "@typespec/html-program-viewer"
+  - "@typespec/http-client-csharp"
+  - "@typespec/http-client-java"
+  - "@typespec/http-server-javascript"
+  - "@typespec/http"
+---
+
+Emitter Framework V2

.chronus/changes/joheredi-efv2-main-2025-1-13-21-57-25.md

@@ -0,0 +1,8 @@
+---
+changeKind: feature
+packages:
+  - "@typespec/emitter-framework"
+  - "@typespec/http-client"
+---
+
+Adding Emitter Framework and Http Client packages

.chronus/changes/joheredi-efv2-main-2025-1-13-5-45-17.md

@@ -0,0 +1,7 @@
+---
+changeKind: feature
+packages:
+  - "@typespec/compiler"
+---
+
+Add Typekits to support EFV2

.prettierrc.json

@@ -9,6 +9,7 @@
   "plugins": [
     "./packages/prettier-plugin-typespec/dist/index.js",
     "./node_modules/prettier-plugin-organize-imports/index.js",
+    "@alloy-js/prettier-plugin-alloy",
     "prettier-plugin-astro",
     "prettier-plugin-sh"
   ],
@@ -19,6 +20,18 @@
         "parser": "typespec"
       }
     },
+    {
+      "files": ["packages/http-client/**/*.tsx"],
+      "options": {
+        "parser": "alloy-ts"
+      }
+    },
+    {
+      "files": ["packages/emitter-framework/**/*.tsx"],
+      "options": {
+        "parser": "alloy-ts"
+      }
+    },
     {
       "files": "*.astro",
       "options": {

cspell.yaml

@@ -88,6 +88,7 @@ words:
   - imple
   - Infima
   - initcs
+  - Initializable
   - inlines
   - inmemory
   - instanceid

package.json

@@ -40,6 +40,7 @@
     "upload-manifest": "pnpm -r --filter=@typespec/http-specs run upload-manifest"
   },
   "devDependencies": {
+    "@alloy-js/prettier-plugin-alloy": "^0.1.0",
     "@chronus/chronus": "^0.14.1",
     "@chronus/github": "^0.4.7",
     "@eslint/js": "^9.18.0",

packages/compiler/src/experimental/typekit/define-kit.ts

@@ -32,6 +32,8 @@ export type StripGuards<T> = {
     : StripGuards<T[K]>;
 };
 
+export const TypekitNamespaceSymbol = Symbol.for("TypekitNamespace");
+
 /**
  * Defines an extension to the Typekit interface.
  *
@@ -43,6 +45,21 @@ export function defineKit<T extends Record<string, any>>(
   source: StripGuards<T> & ThisType<Typekit>,
 ): void {
   for (const [name, fnOrNs] of Object.entries(source)) {
-    TypekitPrototype[name] = fnOrNs;
+    let kits = fnOrNs;
+
+    if (TypekitPrototype[name] !== undefined) {
+      kits = { ...TypekitPrototype[name], ...fnOrNs };
+    }
+
+    // Tag top-level namespace objects with the symbol
+    if (typeof kits === "object" && kits !== null) {
+      Object.defineProperty(kits, TypekitNamespaceSymbol, {
+        value: true,
+        enumerable: false, // Keep the symbol non-enumerable
+        configurable: false,
+      });
+    }
+
+    TypekitPrototype[name] = kits;
   }
 }

packages/compiler/src/experimental/typekit/index.ts

@@ -1,6 +1,6 @@
 import { compilerAssert, Program } from "../../core/index.js";
 import { Realm } from "../realm.js";
-import { Typekit, TypekitPrototype } from "./define-kit.js";
+import { Typekit, TypekitNamespaceSymbol, TypekitPrototype } from "./define-kit.js";
 
 export * from "./define-kit.js";
 export * from "./kits/index.js";
@@ -32,14 +32,16 @@ export function createTypekit(realm: Realm): Typekit {
 
       const value = Reflect.get(target, prop, receiver);
 
+      // Wrap functions to set `this` correctly
       if (typeof value === "function") {
         return function (this: any, ...args: any[]) {
           return value.apply(proxy, args);
         };
       }
 
-      if (typeof value === "object" && value !== null) {
-        return new Proxy(value, handler);
+      // Only wrap objects marked as Typekit namespaces
+      if (typeof value === "object" && value !== null && isTypekitNamespace(value)) {
+        return new Proxy(value, handler); // Wrap namespace objects
       }
 
       return value;
@@ -50,6 +52,11 @@ export function createTypekit(realm: Realm): Typekit {
   return proxy;
 }
 
+// Helper function to check if an object is a Typekit namespace
+function isTypekitNamespace(obj: any): boolean {
+  return obj && !!obj[TypekitNamespaceSymbol];
+}
+
 // #region Default Typekit
 
 const CURRENT_PROGRAM = Symbol.for("TypeSpec.Typekit.CURRENT_PROGRAM");

packages/compiler/src/experimental/typekit/kits/array.ts

@@ -0,0 +1,56 @@
+import { isArrayModelType } from "../../../core/type-utils.js";
+import { Model, Type } from "../../../core/types.js";
+import { defineKit } from "../define-kit.js";
+
+/**
+ * @experimental
+ */
+export interface ArrayKit {
+  /**
+   * Check if a type is an array.
+   */
+  is(type: Type): boolean;
+  /**
+   * Get the element type of an array.
+   */
+  getElementType(type: Model): Type;
+  /**
+   * Create an array type.
+   */
+  create(elementType: Type): Model;
+}
+
+interface TypekitExtension {
+  /** @experimental */
+  array: ArrayKit;
+}
+
+declare module "../define-kit.js" {
+  interface Typekit extends TypekitExtension {}
+}
+
+defineKit<TypekitExtension>({
+  array: {
+    is(type) {
+      return (
+        type.kind === "Model" && isArrayModelType(this.program, type) && type.properties.size === 0
+      );
+    },
+    getElementType(type) {
+      if (!this.array.is(type)) {
+        throw new Error("Type is not an array.");
+      }
+      return type.indexer!.value;
+    },
+    create(elementType) {
+      return this.model.create({
+        name: "Array",
+        properties: {},
+        indexer: {
+          key: this.builtin.integer,
+          value: elementType,
+        },
+      });
+    },
+  },
+});