--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libervia/server/tasks/implicit/task_js_modules.py	Wed Apr 29 17:39:11 2020 +0200
@@ -0,0 +1,71 @@
+#!/ur/bin/env python3
+
+import json
+from pathlib import Path
+from sat.core.i18n import _
+from sat.core.log import getLogger
+from sat.core import exceptions
+from libervia.server.constants import Const as C
+from libervia.server.tasks import task
+
+
+log = getLogger(__name__)
+
+
+class Task(task.Task):
+
+    async def prepare(self):
+        if "js" not in self.resource.browser_modules:
+            raise exceptions.CancelError(f"No JS module needed")
+
+    async def start(self):
+        js_data = self.resource.browser_modules['js']
+        package = js_data.get('package', {})
+        package_path = self.build_path / 'package.json'
+        with package_path.open('w') as f:
+            json.dump(package, f)
+
+        try:
+            cmd = self.findCommand('yarn')
+        except exceptions.NotFound:
+            cmd = self.findCommand('npm')
+        await self.runCommand(cmd, 'install', path=str(self.build_path))
+
+        try:
+            brython_map = js_data['brython_map']
+        except KeyError:
+            pass
+        else:
+            log.info(_("creating JS modules mapping for Brython"))
+            js_modules_path = self.build_path / 'js_modules'
+            js_modules_path.mkdir(exist_ok=True)
+            init_path = js_modules_path / '__init__.py'
+            init_path.touch()
+
+            for module_name, module_data in brython_map.items():
+                log.debug(f"generating mapping for {module_name}")
+                if ' ' in module_name:
+                    raise ValueError(
+                        f"module {module_name!r} has space(s), it must not!")
+                module_path = js_modules_path / f"{module_name}.py"
+                if isinstance(module_data, str):
+                    module_data = {'path': module_data}
+                try:
+                    js_path = module_data.pop('path')
+                except KeyError:
+                    raise ValueError(
+                        f'module data for {module_name} must have a "path" key')
+                module_data['path'] = Path('node_modules') / js_path.strip(' /')
+                export = module_data.get('export') or [module_name]
+                export_objects = '\n'.join(f'{e} = window.{e}' for e in export)
+
+                with module_path.open('w') as f:
+                    f.write(f"""\
+#!/usr/bin/env python3
+from browser import window, load
+{module_data.get('extra_import', '')}
+
+load("{Path('/').joinpath(C.BUILD_DIR, module_data['path'])}")
+{export_objects}
+{module_data.get('extra_init', '')}
+""")