"malformed string" when passing a non-array input from a workflow into an action parameter of type array

SUMMARY

With an action that takes a parameter of type array, I can run the action from the command line and I can even pass a regular string to it, and it seems to figure it out. However if I do the same thing from a workflow (either mistral or orquesta, it doesn't matter, they both fail) and pass a string into an array parameter for an action, things error out badly without a good error message. Improving the error message would be a sufficient remedy; in fact getting the parameter/input field name into the error message would be good too.

ISSUE TYPE

• Bug Report

STACKSTORM VERSION

st2 3.0dev (3438b7c), on Python 2.7.6 (also happens on 2.9.0)

OS / ENVIRONMENT / INSTALL METHOD

st2-docker

STEPS TO REPRODUCE

Install the pack I made that demonstrates the issue:

st2 pack install https://github.com/jeking3/st2-issue-badtype.git

Run the action and pass in a string, see that it works even though the input is of type array - this is because the presence of just one argument is still handled as an array:

root@f34287ba9aa8:/# st2 run badtype.take_array value=hello
.
id: 5bb60780668fd406fff4d76f
status: succeeded
parameters:
  value:
  - hello
result:
  exit_code: 0
  result:
  - hello
  stderr: ''
  stdout: ''

Now run the bad_workflow which attempts to feed the same input from a workflow:

    input:
      value: hello

and the result:

root@f34287ba9aa8:/# st2 run badtype.bad_workflow
.
id: 5bb609d5668fd406fff4d781
action.ref: badtype.bad_workflow
parameters: None
status: failed
start_timestamp: Thu, 04 Oct 2018 12:38:45 UTC
end_timestamp: Thu, 04 Oct 2018 12:38:46 UTC
result:
  errors:
  - message: malformed string
    task_id: task1
  output: null

Do the same thing with good_workflow which sends in:

    input:
      value: [hello]

and the result:

root@f34287ba9aa8:/# st2 run badtype.good_workflow
..
id: 5bb60adc668fd406fff4d78a
action.ref: badtype.good_workflow
parameters: None
status: succeeded
start_timestamp: Thu, 04 Oct 2018 12:43:08 UTC
end_timestamp: Thu, 04 Oct 2018 12:43:11 UTC
result:
  output: null
+--------------------------+------------------------+-------+--------------------+-------------------------------+
| id                       | status                 | task  | action             | start_timestamp               |
+--------------------------+------------------------+-------+--------------------+-------------------------------+
| 5bb60add668fd407a23a2d0e | succeeded (1s elapsed) | task1 | badtype.take_array | Thu, 04 Oct 2018 12:43:09 UTC |
+--------------------------+------------------------+-------+--------------------+-------------------------------+

The workflow log shows:

2018-10-04 12:41:15,293 140443043906416 INFO workflows [-] [5bb60a6a668fd406fff4d784] Requesting execution for task "task1".
2018-10-04 12:41:15,293 140443043906416 INFO workflows [-] [5bb60a6a668fd406fff4d784] Processing task execution request for "task1".
2018-10-04 12:41:15,301 140443043906416 INFO workflows [-] [5bb60a6a668fd406fff4d784] Task execution "5bb60a6b668fd407a23a2d0a" created for task "task1".
2018-10-04 12:41:15,316 140443043906416 DEBUG config_loader [-] Attempting to get config
2018-10-04 12:41:15,317 140443043906416 DEBUG config_loader [-] Config: {}
2018-10-04 12:41:15,318 140443043906416 ERROR workflows [-] [5bb60a6a668fd406fff4d784] Failed task execution for task "task1".
Traceback (most recent call last):
  File "/opt/stackstorm/st2/local/lib/python2.7/site-packages/st2common/services/workflows.py", line 434, in request_task_execution
    ac_ex_ctx
  File "/opt/stackstorm/st2/local/lib/python2.7/site-packages/st2common/util/param.py", line 298, in render_live_params
    live_params = _cast_params_from(params, context, [action_parameters, runner_parameters])
  File "/opt/stackstorm/st2/local/lib/python2.7/site-packages/st2common/util/param.py", line 232, in _cast_params_from
    result[name] = _cast(context[name], param_schema)
  File "/opt/stackstorm/st2/local/lib/python2.7/site-packages/st2common/util/param.py", line 75, in _cast
    return cast(v)
  File "/opt/stackstorm/st2/local/lib/python2.7/site-packages/st2common/util/casts.py", line 39, in _cast_object
    return ast.literal_eval(x)
  File "/usr/lib/python2.7/ast.py", line 80, in literal_eval
    return _convert(node_or_string)
  File "/usr/lib/python2.7/ast.py", line 79, in _convert
    raise ValueError('malformed string')
ValueError: malformed string
2018-10-04 12:41:15,336 140443043906416 DEBUG workflows [-] [5bb60a6a668fd406fff4d784] Updating task execution from state "requested" to "failed".
2018-10-04 12:41:15,354 140443043906416 ERROR workflows [-] [5bb60a6a668fd406fff4d784] Failed task execution for "task1".
Traceback (most recent call last):
  File "/opt/stackstorm/st2/local/lib/python2.7/site-packages/st2actions/workflows/workflows.py", line 145, in handle_workflow_execution
    wf_svc.request_task_execution(wf_ex_db, task_id, task_spec, task_ctx, st2_ctx)
  File "/opt/stackstorm/st2/local/lib/python2.7/site-packages/st2common/services/workflows.py", line 460, in request_task_execution
    raise e
ValueError: malformed string
2018-10-04 12:41:15,373 140443043906416 DEBUG extension [-] found extension EntryPoint.parse('native = orquesta.composers.native:WorkflowComposer')
2018-10-04 12:41:15,374 140443043906416 DEBUG extension [-] found extension EntryPoint.parse('mock = orquesta.composers.mock:WorkflowComposer')
2018-10-04 12:41:15,374 140443043906416 DEBUG extension [-] found extension EntryPoint.parse('mistral = orquesta.composers.mistral:WorkflowComposer')
2018-10-04 12:41:15,375 140443043906416 INFO workflows [-] [5bb60a6a668fd406fff4d784] Updating workflow execution from state "running" to "failed".
2018-10-04 12:41:15,418 140443043906416 ERROR workflows [-] [5bb60a6a668fd406fff4d784] Workflow execution completed with errors. (task_id=u'task1',message=u'malformed string')

EXPECTED RESULTS

I expected to either have it "just work" like the direct action run works, or to have it error out with a message indicating the parameter name that was bad, and why it was bad. In this case saying, "not an array" perhaps instead of "malformed string". I guess the command line argument processing is smart enough to convert all instances of value into array members, but this doesn't happen from a workflow.

ACTUAL RESULTS

See steps to reproduce.

Start with st2common/util/param.py and st2common/util/casts.py, following the traceback through parameter rendering and array casting. Reproduce the failure with the badtype pack and compare it with bad_workflow and good_workflow. Done means the invalid workflow input produces a useful error that identifies the parameter and why its value is invalid.