Show errors when a dependency fails to build with new-build

[oliver-batchelor]

Currently if a dependency fails to build you get no indication of what went wrong, it just stops and I'm left wondering why my project didn't try to build. The option to use -v and find the build log is there of course, but it's not obvious which dependency failed and it's not obvious that is the problem to begin with. I've run into this several times, so I'm guessing it's confused others, too.

cabal new-build
In order, the following will be built (use -v for more details):
elm-bridge-0.4.0
elm-annotate-0.1.0.0
Configuring elm-bridge-0.4.0...
Building elm-bridge-0.4.0...

If I run with verbose I see (still no sign of failure):

Building elm-bridge-0.4.0...
/opt/cabal/1.24/bin/cabal act-as-setup --build-type=Simple -- build
--verbose=2 --builddir=dist
Redirecting build log to {handle:
/home/oliver/.cabal/logs/elm-bridge-0.4.0.log}

Then finally I look into the build log for elm-bridge and I see:

> 
> src/Elm/Derive.hs:43:18: error:
>     Not in scope: data constructor ‘A.Options’
>     Module ‘Data.Aeson.TH’ does not export ‘Options’.
> 

[fgaz]

Judging by the output you are using a pre-2.0 version of cabal-install. I think this is fixed in 2.0