create template-info.yaml

[eriknstevenson]

As suggested here and in support of stack pull request #1988.

[3noch]

Shouldn't the descriptions be part of the template itself? This seems like recipe for confusion, having to do the mapping manually.

[eriknstevenson]

It would be nice to have the descriptions as part of the template files themselves, but would that not require downloading and parsing every template file, every time a user runs stack templates? Granted, they're small files, but I don't see that as being very desirable.

[3noch]

I guess I assumed stack already did download all the templates anyway. I don't actually know either way.

[mgsloan]

Yeah, cloning the template repo would be sensible for many reasons - commercialhaskell/stack#1595.

I don't see much of a problem with having a metadata file like this, though. It might make things clearer if something like template inheritance gets added commercialhaskell/stack#1994

[3noch]

@mgsloan You have a much better sense of what's good in this case. I just like to keep things DRY and having to join these two "tables" adds complexity.

[mgsloan]

@3noch Yeah, the main issue with adding it to the template itself is that it'd be best to have compatibility with older stack versions. So either way, we'll need to add new files. We can either have a template-info file like this, or add a description file per template.

[3noch]

it'd be best to have compatibility with older stack versions.

@mgsloan For how young stack is, this requirement seems a bit hard to believe (again, you know better than I). I would imagine that stack's adoption rate is very good too.

[mgsloan]

We can't just silently make stack new fail for old stack versions. There is no "template repo version check". So our only option would be to make a new repo or a subdir or something.

Overall our backwards / forwards compatibility is extremely good, and we have no reason to sacrifice this.

[3noch]

There is no "template repo version check". So our only option would be to make a new repo or a subdir or something.

Hmm...perhaps that's the main problem? Without any way to describe changes, you can't safely make any!

I.e. perhaps now's a good time to start something like that so that in the future we're not up a creek again?

I'm just offering thoughts. You guys are doing an amazing job already.

[mgsloan]

Yes, something like that would be good for our various sources of data. PRs appreciated

Even with something like that, it seems extreme to flip a switch and disable a feature in all-but-the-newest stack

[eriknstevenson]

As discussed here, testing will now fail if there is any discrepancy between templates listed in template-info.yaml and the actual templates present in the repository.

[3noch]

@Narrative Now that is a good idea!

[mgsloan]

Oops, forgot to merge this after the stack changes got merged. Thanks again!