feat(core): adds node-js detection for rerun/update

README.rst

@@ -84,6 +84,11 @@ Renku commands with the `-S` flag, as in `renku -S <command>`.  More
 information on Git LFS usage in renku can be found in the `Data in Renku
 <https://renku.readthedocs.io/en/latest/user/data.html>`_ section of the docs.
 
+Renku uses CWL to execute recorded workflows when calling `renku update`
+or `renku rerun`. CWL depends on NodeJs to execute the workflows, so installing
+`NodeJs <https://nodejs.org/en/download/package-manager/>`_ is required if
+you want to use those features.
+
 
 .. _pipx-before-reference:
 

renku/core/commands/rerun.py

@@ -24,7 +24,7 @@
 
 def rerun_workflows():
     """Recreate files generated by a sequence of ``run`` commands."""
-    return Command().command(_rerun_workflows).require_migration().require_clean().with_commit()
+    return Command().command(_rerun_workflows).require_migration().require_clean().with_commit().require_nodejs()
 
 
 def _rerun_workflows(client, revision, roots, siblings, inputs, paths):

renku/core/commands/update.py

@@ -37,7 +37,7 @@
 
 def update_workflows():
     """Update existing files by rerunning their outdated workflow."""
-    return Command().command(_update_workflows).require_migration().require_clean().with_commit()
+    return Command().command(_update_workflows).require_migration().require_clean().with_commit().require_nodejs()
 
 
 def _update_workflows(client, revision, no_output, update_all, siblings, paths):

renku/core/errors.py

@@ -462,3 +462,15 @@ class RenkuSaveError(RenkuException):
 
 class DatasetImageError(RenkuException):
     """Raised when a local dataset image is not accessible."""
+
+
+class NodeNotFoundError(RenkuException):
+    """Raised when NodeJs is not installed on the system."""
+
+    def __init__(self):
+        """Build a custom message."""
+        msg = (
+            "NodeJs could not be found on this system\n"
+            "Please install it, for details see https://nodejs.org/en/download/package-manager/"
+        )
+        super(NodeNotFoundError, self).__init__(msg)

renku/core/incubation/command.py

@@ -19,6 +19,7 @@
 
 import contextlib
 import functools
+import shutil
 from collections import defaultdict
 
 import click
@@ -251,6 +252,11 @@ def require_clean(self):
         """Check that the repository is clean."""
         return RequireClean(self)
 
+    @check_finalized
+    def require_nodejs(self):
+        """Ensure nodejs is installed."""
+        return RequireNodeJs(self)
+
     @check_finalized
     def with_communicator(self, communicator):
         """Create a communicator."""
@@ -407,6 +413,28 @@ def build(self):
         return self._builder.build()
 
 
+class RequireNodeJs(Command):
+    """Check that node.js is installed and available on the system."""
+
+    DEFAULT_ORDER = 3
+
+    def __init__(self, builder):
+        """__init__ of DatasetLock."""
+        self._builder = builder
+
+    def _pre_hook(self, builder, context, *args, **kwargs):
+        """Check node is available."""
+        if not shutil.which("nodejs") and not shutil.which("node"):
+            raise errors.NodeNotFoundError()
+
+    @check_finalized
+    def build(self):
+        """Build the command."""
+        self._builder.add_pre_hook(self.DEFAULT_ORDER, self._pre_hook)
+
+        return self._builder.build()
+
+
 class Communicator(Command):
     """Hook for logging and interaction with user."""
 

renku/core/incubation/graph.py

@@ -173,7 +173,7 @@ def _status(client):
 def update():
     """Return a command for generating the graph."""
     command = Command().command(_update).lock_project()
-    return command.require_migration().with_commit(commit_if_empty=False).require_clean()
+    return command.require_migration().with_commit(commit_if_empty=False).require_clean().require_nodejs()
 
 
 def _update(client, dry_run):