I can take a stab at this, but could someone point to me to a historical example where we changed the type of a field? (ex: from str to list[str]) I'm grepped around before and feel like I'm missing something obvious? https://pantsbuild.slack.com/archives/C046T6T9U/p1708710290210289

I don’t know of an example… But, potentially side stepping the question, I’d be wondering about adding list as a possibility in addition to existing behaviour, rather than switching to only a list. Thoughts? (Also, I’ve asked to see if Tyler is interested in contributing, before I saw this, sorry about that.)

hmm, like a

StrListOrMaybeJustStrOption

? No problem, we virtually sit next to each other.

Yeah, something like that; I don’t know if we have existing examples though. Like, physically sit? Cool

Hmm, i'd forgotten that cache-from supports multiple image sources when I added it. To be fair, it's not well documented. I think changing to a list makes sense. Though I also can't find an example of an existing target field like that - should we add a new one

ListOfDictStringToStringField

?

A list-valued option supports

--option=foo

as shorthand for

--option="+['foo']"

(and similarly for config and env vars), so switching to a list-valued option usually doesn't break existing configs or cmd-lines that assumed a scalar of the same type

(I think this is a BUILD field)

We'd want something like this:

docker_image(
    name="with-local-cache-backend",
    cache_to={
        "type": "local",
        "dest": "/tmp/docker-cache/pants-example"
    },
    cache_from=[
    {
        "type": "local",
        "src": "/tmp/docker-cache/pants-example"
    },
    {
        "type": "local",
        "src": "/tmp/docker-cache/pants-example2"
    },
]
)