The problem:
Refer to workflow / action output without explicitly re-publishing the output
values. Why we want it: to reduce repetition, and to make modifications in the
place values are used, not where they are obtained (and not in multiple
places). E.g., as an editor of a workflow, when I just realized that I need a
value of some task down the line, I want to make change right here in the tasks
that consumes the data (and only those which need this data), without finding
and modifying the task that supplies the data.
Reasons:
We don't have a concept of workflow or action ‘results': it's the task which
produces and publishes results. Different tasks call same actions/workflows,
produce same output variables with diff values. We don't want to publish this
output with output name as a key, to the global context: they will conflict and
mess up. Instead, we can namespace them by the task (as specific values are the
attributes of the tasks, and we want to refer to tasks, not actions/workflows).
Solution:
To refer the output of a particular task (aka raw result of action execution
invoked by this task), use the_task prefix:
$_task.<taskname>.<path.to.variable>
$_task.my_task.my_task_result.foo.bar
Expanded example
my_sublfow:
output:
- foo # << declare output here
- bar
tasks:
my_task:
action: get_foo
publish:
foo: $foo # << define output in a task
bar: $bar
...
main_flow_with_explicit_publishing:
tasks:
t1:
workflow: my_subflow
publish:
# Today, you must explicitly publish to make data
# from action available for other tasks
foo: $foo # << re-plublish, else you can't use it
bar: $bar
t2:
action: echo output="$foo and $bar" # << use it from task t1
main_flow_with_implicit_publishing:
tasks:
t1:
workflow: my_subflow
t2:
action: echo output="$_task.t1.foo and $_task.t1.bar"
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