Proposal for 'after' keyword

[cjllanwarne]

Tidies up the call section, and introduces a proposed new after keyword to provide non-output-based dependencies

[geoffjentry]

I thought I was going to hate after but I quite like it.

Is there any harm in allowing after in cases where the outputs already provide a dependency?

[vdauwera]

Ooh I like this idea. I can see this being useful if I want to have a task write to a dB then another read from the db, if there’s no actual file outputs to use as dependencies.

[geoffjentry]

Yeah this is a fairly common complaint. Our stock answer is to wire in a fake output/input but that is horrible. Left to my own devices I’d probably have gone with the ‘dependsOn’ syntax from zamboni but ‘after’ reads so naturally with the call syntax

[cjllanwarne]

@geoffjentry I don't see any harm in allowing both. The after will be redundant if there's already an output-based dependency but it won't break anything. Maybe it even makes things more readable in some cases 🤷‍♂️

[orodeh]

Looks good to me.

[Horneth]

Totally ToL and personal opinion: I find something like andThen easier to reason about since the order of execution matches the left to right order of reading / writing.

[yfarjoun]

I think that if there are multiple dependencies the notation should be less redundant. Perhaps

call x after y and z

or

call x after y,z

[yfarjoun]

@Horneth your suggestion will make it harder to understand the flow of calls since to determine the dependence of call X one would need to examine all the call statements (to see if any of them have andThen X), while with the current proposal, you only need to examine the call X statement.

[geoffjentry]

Agree with @yfarjoun. I think the after syntax fits better into the WDL mantra of simplicity & clarity

[orodeh]

👍

[vdauwera]

👍

[geoffjentry]

👍

[geoffjentry]

This has officially passed on a vote of 3-0 (really 4-0, but I forgot to vote).

As there are no implementations, this will hang out until such time as it actually exists

[abaumann]

one plug for after with dependencies is this: #183

although i dont think this definition requires after to always run, only guaranteed ordering despite dependencies

[geoffjentry]

@abaumann At this point this PR is as-is, which is not to say that one couldn't open a subsequent PR

[geoffjentry]

@cjllanwarne It'd be good to update this to reflect it being against development and not draft-3

[geoffjentry]

Merging as there is an implementation (Cromwell) and there are no conflicts