Do not carry over friendly name with model is or op is

.chronus/changes/friendly-name-no-carry-over-2024-6-9-23-6-32.md

@@ -0,0 +1,18 @@
+---
+# Change versionKind to one of: internal, fix, dependencies, feature, deprecation, breaking
+changeKind: breaking
+packages:
+  - "@typespec/compiler"
+---
+
+Do not carry over `@friendlyName` with `model is` or `op is`
+
+  ```tsp
+  @friendlyName("Abc{T}", T)
+  model Foo<T> {}
+  
+  model Bar is Foo<string>;
+  
+  // This can be changed to
+  model Abcstring is Foo<string>;
+  ```

packages/compiler/src/lib/decorators.ts

@@ -80,15 +80,19 @@ import {
 import { createDiagnostic, reportDiagnostic } from "../core/messages.js";
 import { Program, ProjectedProgram } from "../core/program.js";
 import {
+  AugmentDecoratorStatementNode,
   DecoratorContext,
+  DecoratorExpressionNode,
   Enum,
   EnumMember,
   Interface,
   Model,
   ModelProperty,
   Namespace,
+  Node,
   Operation,
   Scalar,
+  SyntaxKind,
   Type,
   Union,
 } from "../core/types.js";
@@ -1019,6 +1023,27 @@ export const $friendlyName: FriendlyNameDecorator = (
   friendlyName: string,
   sourceObject: Type | undefined
 ) => {
+  // workaround for current lack of functionality in compiler
+  // https://github.com/microsoft/typespec/issues/2717
+  if (target.kind === "Model" || target.kind === "Operation") {
+    if ((context.decoratorTarget as Node).kind === SyntaxKind.AugmentDecoratorStatement) {
+      if (
+        ignoreDiagnostics(
+          context.program.checker.resolveTypeReference(
+            (context.decoratorTarget as AugmentDecoratorStatementNode).targetType
+          )
+        )?.node !== target.node
+      ) {
+        return;
+      }
+    }
+    if ((context.decoratorTarget as Node).kind === SyntaxKind.DecoratorExpression) {
+      if ((context.decoratorTarget as DecoratorExpressionNode).parent !== target.node) {
+        return;
+      }
+    }
+  }
+
   // If an object was passed in, use it to format the friendly name
   if (sourceObject) {
     friendlyName = replaceTemplatedStringFromProperties(friendlyName, sourceObject);

packages/compiler/test/decorators/decorators.test.ts

@@ -350,7 +350,7 @@ describe("compiler: built-in decorators", () => {
 
   describe("@friendlyName", () => {
     it("applies @friendlyName on model", async () => {
-      const { A, B, C } = await runner.compile(`
+      const { A, B } = await runner.compile(`
         @test
         @friendlyName("MyNameIsA")
         model A { }
@@ -363,13 +363,22 @@ describe("compiler: built-in decorators", () => {
         model Templated<T> {
           prop: T;
         }
+        `);
+      strictEqual(getFriendlyName(runner.program, A), "MyNameIsA");
+      strictEqual(getFriendlyName(runner.program, B), "BModel");
+    });
 
+    it(" @friendlyName doesn't carry over to derived models", async () => {
+      const { A, B } = await runner.compile(`
         @test
-        model C is Templated<B>{};
+        @friendlyName("MyNameIsA")
+        model A<T> { t: T; }
+
+        @test
+        model B is A<string> { }
         `);
       strictEqual(getFriendlyName(runner.program, A), "MyNameIsA");
-      strictEqual(getFriendlyName(runner.program, B), "BModel");
-      strictEqual(getFriendlyName(runner.program, C), "TemplatedB");
+      strictEqual(getFriendlyName(runner.program, B), undefined);
     });
   });