Traceback with a workflow with only cwlVersion, class, and empty inputs and outputs

[kinow]

I am writing workflows for the initial sections of the user guide, trying to find the simplest workflow possible to run and validate (Java anecdote: an empty Test.java file is a valid Java file and can be used with javac, being the simplest Java file).

An IndexError traceback was raised for the following workflow:

cwlVersion: v1.2
class: CommandLineTool
inputs: []
outputs: []

(venv) kinow@ranma:~/Development/python/workspace/user_guide$ cwltool /tmp/wf.cwl 
INFO /home/kinow/Development/python/workspace/user_guide/venv/bin/cwltool 3.1.20220406080846
INFO Resolved '/tmp/wf.cwl' to 'file:///tmp/wf.cwl'
INFO [job wf.cwl] /tmp/wf0urglt$ 
ERROR Exception while running job
Traceback (most recent call last):
  File "/home/kinow/Development/python/workspace/user_guide/venv/lib/python3.9/site-packages/cwltool/job.py", line 348, in _execute
    rcode = _job_popen(
  File "/home/kinow/Development/python/workspace/user_guide/venv/lib/python3.9/site-packages/cwltool/job.py", line 986, in _job_popen
    sproc = subprocess.Popen(
  File "/home/kinow/Development/python/miniconda3/lib/python3.9/subprocess.py", line 951, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
  File "/home/kinow/Development/python/miniconda3/lib/python3.9/subprocess.py", line 1691, in _execute_child
    executable = args[0]
IndexError: list index out of range
WARNING [job wf.cwl] completed permanentFail
{}
WARNING Final process status is permanentFail

Expected Behavior

A better error message (assuming this is not a valid CWL Workflow).

Actual Behavior

A traceback.

Workflow Code

cwlVersion: v1.2
class: CommandLineTool
inputs: []
outputs: []

Full Traceback

INFO /home/kinow/Development/python/workspace/user_guide/venv/bin/cwltool 3.1.20220406080846
INFO Resolved '/tmp/wf.cwl' to 'file:///tmp/wf.cwl'
DEBUG Parsed job order from command line: {
    "id": "/tmp/wf.cwl"
}
DEBUG [job wf.cwl] initializing from file:///tmp/wf.cwl
DEBUG [job wf.cwl] {}
DEBUG [job wf.cwl] path mappings is {}
DEBUG [job wf.cwl] command line bindings is []
DEBUG [job wf.cwl] initial work dir {}
INFO [job wf.cwl] /tmp/vuvihs02$ 
ERROR Exception while running job
Traceback (most recent call last):
  File "/home/kinow/Development/python/workspace/user_guide/venv/lib/python3.9/site-packages/cwltool/job.py", line 348, in _execute
    rcode = _job_popen(
  File "/home/kinow/Development/python/workspace/user_guide/venv/lib/python3.9/site-packages/cwltool/job.py", line 986, in _job_popen
    sproc = subprocess.Popen(
  File "/home/kinow/Development/python/miniconda3/lib/python3.9/subprocess.py", line 951, in __init__
    self._execute_child(args, executable, preexec_fn, close_fds,
  File "/home/kinow/Development/python/miniconda3/lib/python3.9/subprocess.py", line 1691, in _execute_child
    executable = args[0]
IndexError: list index out of range
WARNING [job wf.cwl] completed permanentFail
DEBUG [job wf.cwl] outputs {}
DEBUG [job wf.cwl] Removing input staging directory /tmp/1c33c7tl
DEBUG [job wf.cwl] Removing temporary directory /tmp/wbvodmo6
DEBUG Removing intermediate output directory /tmp/vuvihs02
{}
WARNING Final process status is permanentFail

Your Environment

• cwltool version: cwltool 3.1.20220406080846
  Check using cwltool --version