Upgrading Stack to Cabal 2.2

Tue Feb 20 18:02:11 UTC 2018

1. The InstalledPackageInfo license field is also `Either SPDX.License
License` [1] and you can get a list of IPIs conviently with `HcPkg.dump` [2]
2. It's up to you, if `Text` is enough, go for it. In the future you
might want to provide some license reports, where you'll need structured
license information, but then "reverting" `TextualLicense` will be a
type-directed, so it's up to you.

Oleg

-
https://github.com/haskell/cabal/blob/32fea06a1023a507d7dc16b29f542538c0b55e46/Cabal/Distribution/Types/InstalledPackageInfo.hs#L50
-
https://github.com/haskell/cabal/blob/32fea06a1023a507d7dc16b29f542538c0b55e46/Cabal/Distribution/Simple/Program/HcPkg.hs#L246

On 20.02.2018 19:45, Michael Snoyman wrote:
> I'm sorry, I'm not quite sure I understand your recommendation. Are
> you saying that I should ideally replace all usages of `License` in
> the Stack codebase with `Either SPDX.License License`? That _should_
> be possible, the only questions I'd have are:
>
> 1. We additionally grab license info from the GHC package dump. Would
> there be any problem parsing that license field into the old License
> data type and storing as Right?
> 2. If we're going to have to treat this as arbitrary text anyway, is
> there any reason not to represent it as `newtype TextualLicense =
> TextualLicense Text` or similar, and convert immediately with `display`?
>
> On Tue, Feb 20, 2018 at 6:12 PM, Oleg Grenrus <oleg.grenrus at iki.fi
> <mailto:oleg.grenrus at iki.fi>> wrote:
>
>     Hi Michael,
>
>     thanks for your comments!
>
>     - The allBuildInfo change is
>     https://github.com/haskell/cabal/commit/8fc10320a5dc4898927c84ad6a2dce7965ef30db
>     <https://github.com/haskell/cabal/commit/8fc10320a5dc4898927c84ad6a2dce7965ef30db>,
>     I agree with Herbert on this. New `allBuildInfo` implementation is
>     correct given the name. There was even a TODO to make that change.
>     `reallyAllBuildInfo` would been silly. I also didn't felt ok to change
>     the type to `Traversal` (we have lenses, please try out them too and
>     tell if something is missing!). We'll highlight the change in the
>     changelog, as it's easy to miss.
>
>     - The lack of SPDX changelog entry is my bad. It was a series of
>     patches, and the changelog + manual update is still not done. I try to
>     summarise:
>         - `cabal-version: 2.2` files use SPDX expression syntax for
>     `license: ` field. PackageDescription's licenseRaw will be Left expr,
>     expr :: Distribution.SPDX.License.License
>         - `cabal-version: 2.0` files still use old `License` syntax and
>     type, licenseRaw is `Right l`, l :: Distribution.License.License
>         - I recommend treating the field as opaque. You can `either
>     display
>     display` to show it
>            - Next best choice is to use `SPDX.License` as in that
>     direction
>     conversion is lossless (licenseToSPDX), but have to workaround lack of
>     e.g. `OtherLicense` as a concept (IIRC it's converted to
>     LicenseRef:OtherLicense which is valid SPDX-License-Id). This might be
>     necessary if you plan to read (human readable) text back.
>
>     Oleg
>
>     On 20.02.2018 15:47, Michael Snoyman wrote:
>     > Hi all,
>     >
>     > Oleg mentioned to me on Reddit that a 2.2 branch has been cut for
>     > Cabal, and recommended we try to upgrade Stack to it. I'm sharing
>     > information here on that process in case it's useful to others,
>     either
>     > as feedback on the API changes, or help for others going through
>     > similar upgrades. If anyone would rather that I do or do not
>     post such
>     > reports in the future, let me know.
>     >
>     > I've opened a PR for this change[1], which currently is a single
>     > commit[2]. As you can see from the change to stack.yaml[3], I needed
>     > to refer to the commit of Cabal in question, and turn on
>     `allow-newer`
>     > for some packages (cabal-doctest and http-api-data) with restrictive
>     > upper bounds on Cabal. Both of these packages compiled without
>     issue.
>     >
>     > No change was necessary to Stack's Setup.hs file.
>     >
>     > Most of the changes so far were compile-time errors, which is a Good
>     > Thing. Changes I had to make:
>     >
>     > * The build type is no longer a Maybe field. (As a user: this is a
>     > nice change, no longer a need to guess about what a Nothing
>     value means.)
>     > * There are now two License types, the original one and the SPDX
>     > variant. I don't understand what this change is about, some further
>     > explanation in the docs or the ChangeLog would definitely be
>     > appreciated. But hacking my way through the types seems to have
>     worked.
>     > * Parsing a package description now works on a ByteString
>     instead of a
>     > String. This allowed me to remove some UTF8 conversion and
>     > BOM-stripping code, which is very nice.
>     > * The new parsing API exposes the cabal file version when that
>     > prevented the parse (at least, that's my understanding). The changes
>     > to accommodate the new API were relatively trivial, so another
>     +1 here.
>     > * Also: getting file position information for warnings and errors is
>     > _very_ nice. +1
>     >
>     > I haven't done extensive testing yet, but I've so far only found one
>     > bug due to runtime changes: the behavior of allBuildInfo has changed
>     > to now include non-buildable components. This resulted in some
>     > confusion until I reviewed the changelog more closely. If I
>     could make
>     > a request, it would be that, in the future, new runtime behavior
>     come
>     > with a new function name, to convert runtime errors into compile
>     time
>     > errors. This was _not_ a particularly difficult issue to work around
>     > though, in large part thanks to the changelog.
>     >
>     > I'll continue testing this branch of Stack. Our plans are to merge
>     > this to master, and release Stack 1.7.0 close to the Cabal 2.2
>     release
>     > date.
>     >
>     > Michael
>     >
>     > [1] https://github.com/commercialhaskell/stack/pull/3878/files
>     <https://github.com/commercialhaskell/stack/pull/3878/files>
>     > [2]
>     >
>     https://github.com/commercialhaskell/stack/pull/3878/commits/a101341d04213d6dd8e0cf16d2f2fef8e7ed5cd5
>     <https://github.com/commercialhaskell/stack/pull/3878/commits/a101341d04213d6dd8e0cf16d2f2fef8e7ed5cd5>
>     > [3]
>     >
>     https://github.com/commercialhaskell/stack/pull/3878/commits/a101341d04213d6dd8e0cf16d2f2fef8e7ed5cd5#diff-fafd0cdcd559a7b124cc61c29413fb54
>     <https://github.com/commercialhaskell/stack/pull/3878/commits/a101341d04213d6dd8e0cf16d2f2fef8e7ed5cd5#diff-fafd0cdcd559a7b124cc61c29413fb54>
>     >
>     >
>     > _______________________________________________
>     > cabal-devel mailing list
>     > cabal-devel at haskell.org <mailto:cabal-devel at haskell.org>
>     > http://mail.haskell.org/cgi-bin/mailman/listinfo/cabal-devel
>     <http://mail.haskell.org/cgi-bin/mailman/listinfo/cabal-devel>
>
>
>
>     _______________________________________________
>     cabal-devel mailing list
>     cabal-devel at haskell.org <mailto:cabal-devel at haskell.org>
>     http://mail.haskell.org/cgi-bin/mailman/listinfo/cabal-devel
>     <http://mail.haskell.org/cgi-bin/mailman/listinfo/cabal-devel>
>
>

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 819 bytes
Desc: OpenPGP digital signature
URL: <http://mail.haskell.org/pipermail/cabal-devel/attachments/20180220/19c5ae5b/attachment.sig>