Fix stop running decorators on partially instantiated operations (#3227)

fix [#2619](#2619)

Author: timotheeguerin

.chronus/changes/fix-unfinished-partial-ops-2024-3-24-16-10-25.md

@@ -0,0 +1,8 @@
+---
+# Change versionKind to one of: internal, fix, dependencies, feature, deprecation, breaking
+changeKind: fix
+packages:
+  - "@typespec/compiler"
+---
+
+Stop running decorators on partially instantiated operations(When interface is instantiated but not the operation)

packages/compiler/src/core/checker.ts

@@ -2865,7 +2865,7 @@ export function createChecker(program: Program): Checker {
     }
 
     // Some of the mapper args are still template parameter so we shouldn't create the type.
-    return mapper.args.every((t) => t.kind !== "TemplateParameter");
+    return !mapper.partial && mapper.args.every((t) => t.kind !== "TemplateParameter");
   }
 
   function checkModelExpression(node: ModelExpressionNode, mapper: TypeMapper | undefined) {

packages/compiler/src/core/projector.ts

@@ -416,7 +416,9 @@ export function createProjector(
       projectedOp.namespace = projectedNamespaceScope();
     }
 
-    finishTypeForProgram(projectedProgram, projectedOp);
+    if (op.isFinished) {
+      finishTypeForProgram(projectedProgram, projectedOp);
+    }
     if (op.interface) {
       projectedOp.interface = projectType(op.interface) as Interface;
     }

packages/compiler/test/checker/interface.test.ts

@@ -1,5 +1,5 @@
 import { deepStrictEqual, notStrictEqual, ok, strictEqual } from "assert";
-import { beforeEach, describe, it } from "vitest";
+import { beforeEach, describe, expect, it, vi } from "vitest";
 import { isTemplateDeclaration } from "../../src/core/type-utils.js";
 import { Interface, Model, Operation, Type } from "../../src/core/types.js";
 import { getDoc } from "../../src/index.js";
@@ -410,6 +410,25 @@ describe("compiler: interfaces", () => {
       strictEqual(returnType.name, "int32");
     });
 
+    it("instantiating an templated interface doesn't finish template operation inside", async () => {
+      const $track = vi.fn();
+      testHost.addJsFile("dec.js", { $track });
+      testHost.addTypeSpecFile(
+        "main.tsp",
+        `
+        import "./dec.js";
+         
+         interface Base<A> {
+          @track bar<B>(input: A): B;
+        }
+
+        alias My = Base<string>;
+        `
+      );
+      await testHost.compile("./");
+      expect($track).not.toHaveBeenCalled();
+    });
+
     it("emit warning if shadowing parent templated type", async () => {
       const diagnostics = await runner.diagnose(`
       interface Base<A> {