hashicorp/packer-plugin-sdk incompatible with zclconf/go-cty v1.11.0 about go-cty

[apparentlymart]

Hi @mschuchard,

It seems like the Packer SDK is internally relying on the encoding/gob library for its wire serialization. Older versions of cty had some leftover support for gob which I added as a concession to HashiCorp Terraform before the Terraform team realized that gob wasn't going to work anyway, and so I recently removed that concession from cty because it was hampering ongoing maintenance.

It seems unfortunate that HashiCorp Packer was quietly relying on this behavior. I think the best thing to do here is first to see if there's some way that Packer can take responsibility for its own wire encoding concerns (that is: implement the gob encoding itself rather than relying on me to maintain it upstream.) If that isn't possible for some reason then I may consider adding back gob support, but if it comes to that then I'll likely have some design work to figure out how to reintroduce it in a way that doesn't make it so inconvenient to maintain other parts of this library.

I'll wait to see what the Packer team thinks before taking any action here.

[mschuchard]

I see now this overlaps with #132, which was also dual-reported on both trackers (which is how I discovered it). The chosen resolution was to downgrade to go-cty v1.10.0 for use with the packer-sdk.

I believe that this will probably not be acted upon in the packer-sdk, and therefore probably the path forward will be to lock to v1.10.0 for Packer moving forward. Hopefully that is not the case though.

[dbast]

Dependabot update proposals to v1.11.0 score with a compatibility of 3%, see e.g. mkaczanowski/packer-builder-arm#211 That maybe indicates lots of users relying on the packer-plugin-sdk compatibility.