Add npm generator for Emscripten and WebAssembly builds

Introduce a new npm generator in the Conan extensions for deploying to NPM when building for Emscripten and WebAssembly architectures. This generator copies JavaScript and TypeScript declaration files to a distribution directory and creates a package.json file using configuration information from the root package.

Contribute to NP-637

extensions/generators/npm.py

@@ -0,0 +1,27 @@
+import json
+
+from conan import ConanFile
+from conan.tools.files import copy, mkdir, save
+from pathlib import Path
+
+
+class npm:
+    def __init__(self, conanfile: ConanFile):
+        self._conanfile = conanfile
+
+    def generate(self):
+        if self._conanfile.settings.os != "Emscripten":
+            self._conanfile.output.error("Can only deploy to NPM when build for Emscripten")
+            return
+
+        root_package = [dep for dep in self._conanfile.dependencies.direct_host.values()][0]
+        dist_path = Path(self._conanfile.generators_folder, "dist")
+        mkdir(self._conanfile, str(dist_path))
+
+        # Copy the *.js and *.d.ts
+        copy(self._conanfile, "*.js", src=root_package.package_folder, dst=str(dist_path))
+        copy(self._conanfile, "*.d.ts", src=root_package.package_folder, dst=str(dist_path))
+
+        # Create the package.json
+        save(self._conanfile, str(Path(dist_path.parent, "package.json")),
+             json.dumps(root_package.conf_info.get(f"user.{root_package.ref.name.lower()}:package_json")))