dhall-json: yaml-pre-0_11 does not build

[singpolyma]

Says it allows all the way down to yaml 0.5.0, but relies on features introduced in yaml 0.10.2.0 without CPP guards (namely, encodeWith and encoding options)

[quasicomputational]

Ah, that's annoying. It's been broken for a while, then: in #962, I tried to bump it to 0.11 across the board, but bounds rule it out on GHC 7.10. And 0.10.2.0 similarly requires GHC 8.0.

[Gabriella439]

@singpolyma: Do you need dhall-json to build for yaml versions earlier than 0.10.20 or would revising the lower bound to be 0.10.20.0 be an acceptable solution?

[jneira]

Mmm, if yaml-0.10.20.0 doesnt work with ghc-7.10.3, we'll have to remove dhall-json from the appveyor build.
Strangely, the appveyor build for the pr succeded for ghc-7.10.3, using yaml-0.8.21.1. 🤔

[jneira]

nvm, we dropped support for dhall-json with ghc-7.10.3 in #941 (it introduced encodeWith too). So bump up lower bound to 0.10.20.0 would be fine.

[singpolyma]

@singpolyma: Do you need `dhall-json` to build for `yaml` versions earlier than `0.10.20`

Yes. I am maintaining a small local patch for now that allows me to build it -- but it's not a "correct" patch since I just replace calls to encodeWith with calls to encode and ignore the options.

[Gabriella439]

@singpolyma: Note that the change I'm going to make is going to do the same thing (ignore the options for older versions of yaml), because as far as I know specifying the quoting for multi-line literals is not supported at all by older yaml versions. However, that's the only thing it affects and in the worst case scenario it will just generate a weirdly formatted but still valid string literal.

[Gabriella439]

Fix is up here: #981