Upgrading Stack to Cabal 2.2
Michael Snoyman
michael at snoyman.com
Tue Feb 20 18:28:26 UTC 2018
Alright, I've updated the PR to use `Either SPDX.License License`:
https://github.com/commercialhaskell/stack/pull/3878/commits/6679aafe99a087dd6aac341fce965f4067e1be77
The only difference from your description that I ran into is that there's
no Text instance for SPDX.License, meaning instead of:
either display display
I ended up with
display . either licenseFromSPDX id
Is it intentional that there is no Text instance for SPDX.License?
On Tue, Feb 20, 2018 at 8:02 PM, Oleg Grenrus <oleg.grenrus at iki.fi> wrote:
> 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/32fea06a1023a507d7dc16b29f5425
> 38c0b55e46/Cabal/Distribution/Types/InstalledPackageInfo.hs#L50
> -
> https://github.com/haskell/cabal/blob/32fea06a1023a507d7dc16b29f5425
> 38c0b55e46/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>
> > >
> > >
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