Hi All,

Warning output is squelched when referring to external locations. Warning output is produced on the console when -Werror is present. The following pair of projects demonstrates the problem on the latest version of stack (1.1.2).

STACK_TEST.zip

This pair of projects was produced and tested with the following sequence of actions.

Check your stack version.

$ stack --version
Version 1.1.2 x86_64 hpack-0.14.0

Create two new projects.

stack new stacktest
stack new stackdep

Edit the stack.yaml file in stacktest to match the following.

resolver: lts-6.14

packages:
- '.'
- location: ../stackdep

extra-deps: []

flags: {}

extra-package-dbs: []

Edit src/Lib.hs in stacktest to match the following.

module Lib
    ( someFunc
    ) where

thisShouldGenerateAWarning = undefined

someFunc :: IO ()
someFunc = putStrLn "someFunc"

Edit stacktest.cabal to resemble the following. Of note is the ghc-options line.

$ cat stacktest/stacktest.cabal
name:                stacktest
version:             0.1.0.0
synopsis:            Initial project template from stack
description:         Please see README.md
homepage:            https://github.com/sw17ch/stacktest#readme
license:             BSD3
license-file:        LICENSE
author:              John Van Enk
maintainer:          [email protected]
copyright:           2016 John Van Enk
category:            Web
build-type:          Simple
-- extra-source-files:
cabal-version:       >=1.10

library
  hs-source-dirs:      src
  exposed-modules:     Lib
  build-depends:       base >= 4.7 && < 5
  default-language:    Haskell2010
  ghc-options:         -Wall

EXPECTED: two warnings in the build output of src/Lib.hs when building stacktest.

    /Users/johnvanenk/STACK_TEST/stacktest/src/Lib.hs:5:1: Warning:
        Defined but not used: ‘thisShouldGenerateAWarning’

    /Users/johnvanenk/STACK_TEST/stacktest/src/Lib.hs:5:1: Warning:
        Top-level binding with no type signature:
          thisShouldGenerateAWarning :: forall t. t

ACTUAL: no warning output is emitted.

$ stack build
stackdep-0.1.0.0: unregistering (local file changes: src/StackDep.hs stackdep.cabal)
stacktest-0.1.0.0: configure
stacktest-0.1.0.0: build
stackdep-0.1.0.0: configure
stacktest-0.1.0.0: copy/register
stackdep-0.1.0.0: build
stackdep-0.1.0.0: copy/register
Completed 2 action(s).

Further notes.

The warnings are still present in the log files, but no indications that warnings exist in the build are present on the console.

$ grep -Irn Warning .
./.stack-work/logs/stacktest-0.1.0.0.log:5:src/Lib.hs:5:1: Warning:
./.stack-work/logs/stacktest-0.1.0.0.log:6:    Defined but not used: ‘thisShouldGenerateAWarning’
./.stack-work/logs/stacktest-0.1.0.0.log:8:src/Lib.hs:5:1: Warning:
./.stack-work/logs/stacktest-0.1.0.0.log:10:      thisShouldGenerateAWarning :: forall t. t

Furthermore, turning on -Werror produces the warning output as expected, but is sometimes awkward when doing large refactors.

This behavior does not appear to exist when using extra-deps without a package in some other location as specified by a location directive.