Raise exception for non-Emscripten deployments in npm.py

Replace error logging with an exception to ensure that the code explicitly fails when attempting to deploy to NPM without Emscripten. This change enhances error handling by providing a clearer indication of incorrect deployment conditions.

Contribute to NP-637

extensions/generators/npm.py

@@ -1,7 +1,8 @@
 import json
 
 from conan import ConanFile
-from conan.tools.files import copy, mkdir, save
+from conan.errors import ConanException
+from conan.tools.files import copy, save
 from pathlib import Path
 
 
@@ -12,7 +13,7 @@ class npm:
     def generate(self):
         if self._conanfile.settings.os != "Emscripten":
             self._conanfile.output.error("Can only deploy to NPM when build for Emscripten")
-            return
+            raise ConanException("Can only deploy to NPM when build for Emscripten")
 
         root_package = [dep for dep in self._conanfile.dependencies.direct_host.values()][0]