fix: conditionally import param and requestBody in controller template

The OpenAPI controller template unconditionally imported `param` and
`requestBody` decorators from `@loopback/rest`, even when the
generated controller did not use any parameters or request bodies.

This caused ESLint errors with `no-unused-imports` rule and was
confusing for developers reading the generated code.

Changes:
- Track whether `@param` and `@requestBody` decorators are used
  in controller methods
- Conditionally import these decorators in the template only when needed

Fixes #3335

Author: mmustafasenoglu

packages/cli/generators/openapi/spec-helper.js

@@ -455,6 +455,13 @@ function buildControllerSpecs(operationsMapByController, options) {
     controllerSpec.methods = entry.operations.map(op =>
       buildMethodSpec(controllerSpec, op, options),
     );
+    // Track whether param and requestBody decorators are used
+    controllerSpec.usesParam = controllerSpec.methods.some(m =>
+      m.signature && m.signature.includes('@param('),
+    );
+    controllerSpec.usesRequestBody = controllerSpec.methods.some(m =>
+      m.signature && m.signature.includes('@requestBody('),
+    );
     controllerSpec.methodMappingObject = printSpecObject(
       controllerSpec.methodMapping,
     );

packages/cli/generators/openapi/templates/src/controllers/controller-template.ts.ejs

@@ -1,4 +1,4 @@
-import {api, operation, param, requestBody} from '@loopback/rest';<%if (withImplementation) { %>
+import {api, operation<% if (usesParam) { %>, param<% } %><% if (usesRequestBody) { %>, requestBody<% } %>} from '@loopback/rest';<%if (withImplementation) { %>
 import {inject} from '@loopback/core';
 
 import {<%- serviceClassName %>} from '../services';