Custom setup breaks with ghcjs

[nomeata]

While having a recent ghcjs based on GHC-8.0 in my $PATH I tried to build a package that depends on gc (as an example for a package with a custom setup file) with the following cabal file:

name:                foo
version:             0.1.0.0
license:             BSD3
license-file:        LICENSE
author:              Joachim Breitner
maintainer:          mail@joachim-breitner.de
build-type:          Simple
extra-source-files:  ChangeLog.md
cabal-version:       >=1.10

library
  build-depends:       base >=4.9 && <4.10, gc
  default-language:    Haskell2010

and I got this:

/tmp/foo $ cabal new-build --ghcjs
Warning: don't know how to find change monitoring files for the installed
package databases for ghcjs
Resolving dependencies...
Warning: don't know how to find change monitoring files for the installed
package databases for ghcjs
In order, the following will be built (use -v for more details):
cabal-doctest-1.0.2
gc-0.0.2
foo-0.1.0.0
Configuring cabal-doctest-1.0.2...
Building cabal-doctest-1.0.2...
Preprocessing library cabal-doctest-1.0.2...
[1 of 1] Compiling Distribution.Extra.Doctest ( src/Distribution/Extra/Doctest.hs, dist/build/Distribution/Extra/Doctest.js_o )
Installing library in
/home/jojo/.cabal/store/ghcjs-0.2.1/cabal-doctest-1.0.2-b6c060cc4355571b3c7bde4854f8b4df7631e45f3e680c034a5d1e374280b376/lib
Creating package registration file:
/tmp/foo/dist-newstyle/tmp/package-registration-11015139291801979802
[1 of 1] Compiling Main             ( /tmp/foo/dist-newstyle/tmp/gc-17531/gc-0.0.2/dist/setup/setup.hs, /tmp/foo/dist-newstyle/tmp/gc-17531/gc-0.0.2/dist/setup/Main.js_o )
Linking /tmp/foo/dist-newstyle/tmp/gc-17531/gc-0.0.2/dist/setup/setup.jsexe (Main)
Configuring gc-0.0.2...
setup: The program 'ghcjs' version >=0.1 is required but the version of
/home/jojo/.bin/ghcjs could not be determined.

This happens both with cabal being 1.24 and today’s HEAD (2.1).

What can I do about this (without patching gc or so)?

[nomeata]

I think in both cases the ghcjs-provided Cabal-1.24 is used to build the custom setup program.

[nomeata]

I tried to force it to use a newer Cabal to build the custom setup program, but it seems that --constraint Cabal >=2.0 is being ignored when it comes to determining the dependencies for setup files. Is there a way I can make cabal use a newer Cabal when building gc’s setup?

(But it would not help anyways, if I patch gc to use Cabal-2.0, I still get this error.)

[nomeata]

The problem is not specific to new-build, the problem can be observed simply with

$ cabal-2.1 install gc --ghcjs
Resolving dependencies...
[1 of 1] Compiling Main             ( /tmp/cabal-tmp-21904/gc-0.0.2/dist/setup/setup.hs, /tmp/cabal-tmp-21904/gc-0.0.2/dist/setup/Main.js_o )
Linking /tmp/cabal-tmp-21904/gc-0.0.2/dist/setup/setup.jsexe (Main)
Configuring gc-0.0.2...
setup: The program 'ghcjs' version >=0.1 is required but the version of
/home/jojo/.bin/ghcjs could not be determined.
Failed to install gc-0.0.2
cabal-2.1: Error: some packages failed to install:
gc-0.0.2-AiSszylvpSAHDmEyMbsnAn failed during the configure step. The
exception was:
ExitFailure 1

[23Skidoo]

Is there a way I can make cabal use a newer Cabal when building gc’s setup?

Try using --constraint=setup.Cabal >=2 or --constraint=gc:setup.Cabal >=2. See here for more info about setup constraints.

[nomeata]

Not specific to cabal-install at all, purely a Cabal/ghcjs problem:

/tmp/gc-0.0.2 $ ghcjs --make Setup.lhs 
Linking Setup.jsexe (Main)
/tmp/gc-0.0.2 $ node Setup.jsexe/all.js configure --ghcjs
Configuring gc-0.0.2...
all.js: The program 'ghcjs' version >=0.1 is required but the version of
/home/jojo/.bin/ghcjs could not be determined.

[nomeata]

I might be hitting the problem described in commercialhaskell/stack#1496

[23Skidoo]

@nomeata Does compiling the setup script with 2.0 help?

[nomeata]

Nope. same problem, reproduced with:

$ cabal install --ghcjs Cabal-2.0.0.2
$ ghcjs --make Setup.lhs -v
-- checking that indeed `Cabal-2.0.0.2` is used
$ node Setup.jsexe/all.js configure --ghcjs 

[23Skidoo]

What is the output of /home/jojo/.bin/ghcjs --version?

[nomeata]

$ /home/jojo/.bin/ghcjs --version
The Glorious Glasgow Haskell Compilation System for JavaScript, version 0.2.1 (GHC 8.0.2)

[23Skidoo]

Does /home/jojo/.bin/ghcjs --numeric-ghcjs-version work? That's the method used by Cabal to determine GHCJS version.

[nomeata]

$ /home/jojo/.bin/ghcjs --numeric-ghcjs-version
0.2.1

[nomeata]

According to strace -e read,write,execve -f node Setup.jsexe/all.js configure --ghcjs -v3, ghcjs --numeric-ghcjs-version is not even called. I wonder if there is something severely wrong with GHCJS/node.

[23Skidoo]

/cc @luite

[nomeata]

Ah, I see something. With -v3 I get

Warning: cannot determine version of /home/jojo/.bin/ghcjs :
"Linking a.jsexe ()\n"

So somehow instead of the version number the Setup code is trying to parse this string. But where does it come from?

[23Skidoo]

-v3 should tell you what programs Cabal invoked.

[nomeata]

Full output:

/tmp/gc-0.0.2 $ node Setup.jsexe/all.js configure --ghcjs -v3
Configuring gc-0.0.2...
creating dist/build
Searching for ghcjs in path.
Found ghcjs at /home/jojo/.bin/ghcjs
/home/jojo/.bin/ghcjs --numeric-ghcjs-version
Warning: cannot determine version of /home/jojo/.bin/ghcjs :
"Linking a.jsexe ()\n"
CallStack (from HasCallStack):
  die', called at ./Distribution/Simple/Program/Db.hs:484:18 in Cabal-2.0.0.2-FM1cexNFvRMK0jH27C02s:Distribution.Simple.Program.Db
  requireProgramVersion, called at ./Distribution/Simple/GHCJS.hs:61:5 in Cabal-2.0.0.2-FM1cexNFvRMK0jH27C02s:Distribution.Simple.GHCJS
  configure, called at ./Distribution/Simple/Configure.hs:1592:14 in Cabal-2.0.0.2-FM1cexNFvRMK0jH27C02s:Distribution.Simple.Configure
  configCompilerEx, called at ./Distribution/Simple/Configure.hs:395:12 in Cabal-2.0.0.2-FM1cexNFvRMK0jH27C02s:Distribution.Simple.Configure
  configure, called at ./Distribution/Simple.hs:570:20 in Cabal-2.0.0.2-FM1cexNFvRMK0jH27C02s:Distribution.Simple
  confHook, called at ./Distribution/Simple/UserHooks.hs:67:5 in Cabal-2.0.0.2-FM1cexNFvRMK0jH27C02s:Distribution.Simple.UserHooks
  configureAction, called at ./Distribution/Simple.hs:174:19 in Cabal-2.0.0.2-FM1cexNFvRMK0jH27C02s:Distribution.Simple
  defaultMainHelper, called at ./Distribution/Simple.hs:119:27 in Cabal-2.0.0.2-FM1cexNFvRMK0jH27C02s:Distribution.Simple
  defaultMain, called at Setup.lhs:30:8 in main:Main
all.js: The program 'ghcjs' version >=0.1 is required but the version of
/home/jojo/.bin/ghcjs could not be determined.

[nomeata]

Fun fact:

$ /home/jojo/.bin/ghcjs ""
Linking a.jsexe ()

and indeed, it seems that ghcjs is called with an empty string as an argument

[pid 16650] execve("/home/jojo/.bin/ghcjs", ["/home/jojo/.bin/ghcjs", ""], [/* 55 vars */] <unfinished ...>

[23Skidoo]

Looks like the same happens when /home/jojo/.bin/ghcjs --numeric-ghcjs-version is invoked programmatically by Cabal.

[nomeata]

Ok, it is definitely a problem with ghcjs and/or node:

/tmp $ cat Test.hs 
import System.Process
main = rawSystem "ghcjs" ["--numeric-ghcjs-version"]
/tmp $ ghcjs -O Test.hs 
[1 of 1] Compiling Main             ( Test.hs, Test.js_o )
Linking Test.jsexe (Main)
/tmp $ node Test.jsexe/all.js
Linking a.jsexe ()

[23Skidoo]

I guess that this ticket can be closed then since this is not a bug in Cabal?