MissingH 1.4.0.1 and parsec 3.1.12.0 are not compatible

[Rufflewind]

MissingH 1.4.0.1 and parsec 3.1.12.0 are not compatible because the Text.ParserCombinators.Parsec module is no longer Safe. It used to be Safe in version 3.1.11.

This incompatibility breaks upstream packages such as Gitit (see comment by cidig on 2018-02-04).

Issue in MissingH repo: haskell-hvr/missingh#42

src/Text/ParserCombinators/Parsec/Utils.hs:33:1: error:
    Text.ParserCombinators.Parsec: Can't be safely imported!
    The module itself isn't safe.
   |
33 | import Text.ParserCombinators.Parsec
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[hvr]

SafeHaskell strikes again... why do people keep relying on not-advertised module safety properties? :-/

PS: btw, I was wondering if anyone was still using the legacy Text.ParserCombinators.* namespace, as I was considering removing it at some point (we have a parsec2 package that would provide the legacy API).

PS2: This is gonna take a bit of time to figure out a way how to get this done w/o CPP; in the mean-time I've tweaked the preferred-versions on Hackage to discourage the solver from picking up parsec-3.1.12.0 unless forced to.

[hvr]

This should be resolved with the release of parsec-3.1.13.0 which is the first release to intentionally provide SafeHaskell support; iow, if your package breaks unless parsec has Safe/Trustworthy modules, then parsec-3.1.13.0 is the first version that actually guarantees this as part of its API contract; see also https://hackage.haskell.org/package/parsec-3.1.13.0/changelog

TLDR: if you require SafeHaskell, declare this API requirement by either specifying

build-depends: parsec >= 3.1.13.0 && < 3.2

or, starting with cabal-version:2.0 (c.f. cabal user guide), via

build-depends: parsec ^>= 3.1.13.0

[Rufflewind]

Thanks for the quick resolution!