Stack 1.3.0 no longer notices system-installed ghc

[unhammer]

General summary/comments (optional)

Stack 1.3.0 on Ubuntu no longer notices system-installed ghc (worked fine on 1.2.0)

Steps to reproduce

On Ubuntu 16.04,

• Install ghc-7.8.4 happy-1.19.5 alex-3.1.4 from http://ppa.launchpad.net/hvr/ghc/ubuntu
• export PATH="/opt/ghc/7.8.4/bin:/opt/happy/1.19.5/bin:/opt/alex/3.1.4/bin:$PATH"
• Put resolver: lts-2.22 in stack.yaml
• stack build

Expected

build using system ghc

Actual

stack complains

$ stack build
No compiler found, expected minor version match with ghc-7.8.4 (x86_64) (based on resolver setting in /home/kiwibird/src/app/stack.yaml).
To install the correct GHC into /home/kiwibird/.stack/programs/x86_64-linux/, try running "stack setup" or use the "--install-ghc" flag. To use your system GHC installation, run "stack config set system-ghc --global true", or use the "--system-ghc" flag.

The verbose version also says

@(Data/Store/VersionTagged.hs:72:13)
2016-12-13 11:38:24.242953: [debug] Run process: /sbin/ldconfig -p
@(System/Process/Read.hs:306:3)
2016-12-13 11:38:24.261096: [debug] Process finished in 17ms: /sbin/ldconfig -p
@(System/Process/Read.hs:306:3)
2016-12-13 11:38:24.263701: [debug] Run process: /usr/bin/gcc -v
@(System/Process/Read.hs:306:3)
2016-12-13 11:38:24.267995: [debug] Process finished in 3ms: /usr/bin/gcc -v
@(System/Process/Read.hs:306:3)
2016-12-13 11:38:24.269052: [debug] PIE enabled
@(Stack/Setup.hs:574:17)
2016-12-13 11:38:24.271102: [debug] Found shared library libtinfo.so.5 in 'ldconfig -p' output
@(Stack/Setup.hs:550:29)
2016-12-13 11:38:24.272860: [debug] Did not find shared library libtinfo.so.6
@(Stack/Setup.hs:564:38)
2016-12-13 11:38:24.273324: [debug] Did not find shared library libncursesw.so.6
@(Stack/Setup.hs:564:38)
2016-12-13 11:38:24.273635: [debug] Found shared library libgmp.so.10 in 'ldconfig -p' output
@(Stack/Setup.hs:550:29)
2016-12-13 11:38:24.273980: [debug] Did not find shared library libgmp.so.3
@(Stack/Setup.hs:564:38)
2016-12-13 11:38:24.274057: [debug] Using standard GHC build
@(Stack/Setup.hs:597:9)
2016-12-13 11:38:24.274848: [debug] Run process: /opt/ghc/7.8.4/bin/ghc --info
@(System/Process/Read.hs:306:3)
2016-12-13 11:38:24.330140: [debug] Process finished in 55ms: /opt/ghc/7.8.4/bin/ghc --info

first.

Stack version

$ stack --version
Version 1.3.0, Git revision 99b910d3c8e183aa376cb1e6f0341d86aed6d00e (4372 commits) x86_64 hpack-0.15.0

Method of installation

• Official binary from fpcomplete's apt repo

[borsboom]

From the Major Changes section of the changelog:

Stack will now always use its own GHC installation, even when a suitable GHC installation is available on the PATH. To get the old behaviour, use the --system-ghc flag or run stack config set system-ghc --global true. Docker- and Nix-enabled projects continue to use the GHC installations in their environment by default.

NB: Scripts that previously used stack in combination with a system GHC installation should now include a stack setup line or use the --install-ghc flag. #2221

[unhammer]

I already tried this:

$ stack config set system-ghc --global true
No compiler found, expected minor version match with ghc-7.8.4 (x86_64) (based on resolver setting in /home/kiwibird/src/app/stack.yaml).
To install the correct GHC into /home/kiwibird/.stack/programs/x86_64-linux/, try running "stack setup" or use the "--install-ghc" flag. To use your system GHC installation, run "stack config set system-ghc --global true", or use the "--system-ghc" flag.

And I guess I gave up too early; I did get it compiling with stack build --system-ghc or manually setting system-ghc: true in ~/.stack/config.yaml.

Should I open a separate bug for the stack config set system-ghc --global true failure?

[borsboom]

@unhammer: yes, please open a new issue; it does seem like stack config should work without a compiler installed.