Build error with stack (no cabal) and ghc-9.0.2

[jneira]

Hi, we are trying to add support for ghc-9.0.2 in hls here: https://github.com/haskell/haskell-language-server/pull/2567 The cabal build of ghc-lib-parser-ex-9.0.0.6 is succesful but the stack one is failing with several errors like:

ghc-lib-parser-ex                 > /tmp/stack-f10fe8295758b94c/ghc-lib-parser-ex-9.0.0.6/src/Language/Haskell/GhclibParserEx/GHC/Settings/Config.hs:59:20: error:
ghc-lib-parser-ex                 >     Ambiguous occurrence ‘PlatformMisc’
ghc-lib-parser-ex                 >     It could refer to
ghc-lib-parser-ex                 >        either ‘GHC.Settings.PlatformMisc’,
ghc-lib-parser-ex                 >               imported from ‘GHC.Settings’ at src/Language/Haskell/GhclibParserEx/GHC/Settings/Config.hs:19:1-19
ghc-lib-parser-ex                 >               (and originally defined in ‘ghc-boot-9.0.2:GHC.Platform’)
ghc-lib-parser-ex                 >            or ‘GHC.Platform.PlatformMisc’,
ghc-lib-parser-ex                 >               imported from ‘GHC.Platform’ at src/Language/Haskell/GhclibParserEx/GHC/Settings/Config.hs:18:1-19
ghc-lib-parser-ex                 >    |
ghc-lib-parser-ex                 > 59 |     platformMisc = PlatformMisc {}
ghc-lib-parser-ex                 >    |  

Errors are all related with platform* definitions.

It may be a error in out stack.yaml but i am not getting to identify it, thanks in advance

[shayne-fletcher]

can i see the stack.yaml please and i presume the build compiler is 9.0.2? does adding

flags:
  ghc-lib-parser-ex:
    auto: false
    no-ghc-lib: false

help?

[jneira]

thanks for the fast response yeah we are using compiler: ghc-9.0.2 in our stack.yaml (https://github.com/jneira/haskell-language-server/blob/ghc-9.0.2/stack-9.0.2.yaml) will try those flags, thanks for the tip!

[shayne-fletcher]

i've reproduced it. the issue is having ghc-boot-9.0.1 in the extra-deps. it conflicts perfectly with symbols in ghc-lib-parser-ex

[jneira]

Afair I had to use that cause I got errors with ghc-boot-9.2.1 and ghc-boot-9.0.2 was not available Otoh in the error it mentions ghc-boot-9.0.2 (and originally defined in ‘ghc-boot-9.0.2:GHC.Platform’) so I thought the build was using it somewhat

[shayne-fletcher]

i expect allow-newer:true is why ghc-boot is upgrading to ghc-9.0.2 (wrong - see below) but the point is the presence of this extra-dep is what is creating the problem.

(1) if you download https://hackage.haskell.org/package/ghc-lib-parser-ex-9.0.0.6/ghc-lib-parser-ex-9.0.0.6.tar.gz (2) then stack build with this stack.yaml

resolver: nightly-2022-01-10

packages:
  - .

extra-deps:
- ghc-boot-9.0.1

allow-newer: true

this conflict results. if instead you write

resolver: nightly-2022-01-10

packages:
  - .

it builds ok.

[shayne-fletcher]

i think i get it. auto is on by default and the build compiler is 9.0.2. so this stanza applies

  if flag(auto) && impl(ghc >= 9.0.0) && impl(ghc < 9.1.0)
    build-depends:
      ghc == 9.0.*,
      ghc-boot-th,
      ghc-boot

ghc-boot-9.0.2 is shipped with ghc-9.0.2 and linked in. extra-deps is injecting ghc-9.0.1 from hackage into the mix and they are in conflict somehow? anyway removing ghc-boot-9.0.1 from extra-deps fixes it and since that library (actually, ghc-boot-9.0.2) ships with the build compiler it begs the question of why it is there (in extra-deps) in the first place?

writing

flags:
  ghc-lib-parser-ex:
    auto: false
    no-ghc-lib: false

"fixes" it because now this is the stanza involved,

        build-depends:
          ghc-lib-parser

ghc-boot is not linked. ghc-lib-parser-ex is forced to bind to ghc-lib-parser for all versions of build compiler and never ghc-boot

[jneira]

Hi, i am trying again all the steps i did before reach ghc-boot-9.0.1:

• Same stack.yaml commenting out any ghc-boot entry (so equivalent to your working example?)

In the dependencies for ghc-lib-parser-ex-9.0.0.6:
    ghc-boot needed, but this GHC boot package has been pruned (issue #4510); you need to add the
             package explicitly to extra-deps  (latest matching version is 9.2.1)
needed due to hls-hlint-plugin-1.0.2.1 -> ghc-lib-parser-ex-9.0.0.6
....
Some different approaches to resolving this:

  * Recommended action: try adding the following to your extra-deps in D:\hls\stack-9.0.2.yaml:

- ghc-boot-9.2.1@sha256:a9360b160d72d567d06d0e4bac35f1d2866eeb4f13c83b61b02645dfbbf49848,2795

(stack asks me to add all boot packages, not only ghc-boot, also process, time,..)

now double checking add ghc-boot-9.2.1 as suggested (although does not make much sense imo):

[shayne-fletcher]

remove ghc-boot from extra-deps as before & try:

flags:
  hlint:
    ghc-lib: true
  ghc-lib-parser-ex:
    auto: false
    no-ghc-lib: false

this forces hlint & ghc-lib-parser-ex to not link ghc (ghc-boot) but rather ghc-lib-parser.

[shayne-fletcher]

for reference see https://blog.shaynefletcher.org/2021/02/configuring-cabal-build-flags.html

[shayne-fletcher]

hls-hlint-plugin-1.0.2.1

i'm relying on its cabal file supporting this flag in the same way hlint does?

[shayne-fletcher]

looks like we want to try

flags:
  hls-hlint-plugin:
    ghc-lib: true
  ghc-lib-parser-ex:
    auto: false
    no-ghc-lib: false

[shayne-fletcher]

this section of hls-hlint-plugin-1.0.2.1

  if (flag(hlint33))
    -- This mirrors the logic in hlint.cabal for hlint-3.3
    -- https://github.com/ndmitchell/hlint/blob/d3576de4529d8df6cca5a345f5b7e04474ff7bff/hlint.cabal#L79-L88
    -- so we can make sure that we do the same thing as hlint
    build-depends: hlint ^>=3.3
    if (!flag(ghc-lib) && impl(ghc >=9.0.1) && impl(ghc <9.1.0))
      build-depends: ghc ==9.0.*
    else
      build-depends:
        , ghc
        , ghc-lib            ^>=9.0
        , ghc-lib-parser-ex  ^>=9.0

      cpp-options:   -DHLINT_ON_GHC_LIB

  else
    -- This mirrors the logic in hlint.cabal for hlint-3.2
    -- https://github.com/ndmitchell/hlint/blob/c7354e473c7d09213c8adc3dc94bf50a6eb4a42d/hlint.cabal#L79-L88
    build-depends: hlint ^>=3.2
    if (!flag(ghc-lib) && impl(ghc >=8.10.1) && impl(ghc < 8.11.0))
      build-depends: ghc >=8.10 && <9.0
    else
      build-depends:
        , ghc
        , ghc-lib            ^>=8.10.7.20210828
        , ghc-lib-parser-ex  ^>=8.10

      cpp-options:   -DHLINT_ON_GHC_LIB

looks off. all build paths seem to include ghc that seems wrong. also, the comment indicates that it's consistent with hlint's cabal. it doesn't look like that to me

[shayne-fletcher]

to be clear, i think

      build-depends:
        , ghc
        , ghc-lib            ^>=9.0
        , ghc-lib-parser-ex  ^>=9.0

should read

      build-depends:
          ghc-lib            ^>=9.0
        , ghc-lib-parser-ex  ^>=9.0

for example

update: on second thoughts, this is probably intentional and fine.

[shayne-fletcher]

hmmm and we may need all of

flags:
  hlint:
    ghc-lib: true
  hls-hlint-plugin:
    ghc-lib: true
  ghc-lib-parser-ex:
    auto: false
    no-ghc-lib: false

i think this should work. please let me know.

[shayne-fletcher]

it's not very satisfying but with this patch ghc-lib-parser-ex builds

diff --git a/stack-9.0.2.yaml b/stack-9.0.2.yaml
index f5579777..e8c35cb1 100644
--- a/stack-9.0.2.yaml
+++ b/stack-9.0.2.yaml
@@ -69,6 +69,7 @@ extra-deps:
 - process-1.6.13.2
 - time-1.12.1
 - unix-2.7.2.2
+- hpc-0.6.0.3

 # currently needed for ghcide>extra, etc.
 allow-newer: true
@@ -85,6 +86,7 @@ configure-options:
     - --disable-library-for-ghci

 flags:
+
   haskell-language-server:
     pedantic: true

@@ -97,7 +99,13 @@ flags:
     BuildExecutable: false
   # Stack doesn't support automatic flags.
   hls-hlint-plugin:
+    ghc-lib: true
     hlint33: true
+  hlint:
+    ghc-lib: true
+  ghc-lib-parser-ex:
+    auto: false
+    no-ghc-lib: false
   hyphenation:
     embed: true

which maybe unblocks you a bit for now. the build later fails on ormolu though.

[shayne-fletcher]

i was able to build hs-lint-plugin with no boot libraries in extra deps and no cabal flags using https://gist.github.com/shayne-fletcher/9c2d5c1b0dd21b31a67673a5df084800#file-stack-yaml

i think that indicates that ghc-lib-parser-ex & hlint are sound and the problems start somewhere else in the build.

the converse build with the cabal flags forcing ghc-lib was unsuccessful.

[jneira]

Thanks a lot for take a look and the suggestions, will try. I wonder why this did not happened with ghc-9.0.1 (Afair).

i think that indicates that ghc-lib-parser-ex & hlint are sound and the problems start somewhere else in the build.

I see, the fact that cabal works somewhat suggested it

[shayne-fletcher]

you're welcome. i learned a lot. for the avoidance of doubt, please do not enable flags for hlint, ghc-lib-parser-ex, hls-hlint-plugin to use ghc-lib packages as i was suggesting above as a potential workaround. afaict, that it is not a valid build mode for this project. instead, i would start with the stack.yaml that builds hls-hlint-plugin and add back targets until you find the one that induces the breakage. good luck!

[jneira]

now double checking add ghc-boot-9.2.1 as suggested (although does not make much sense imo):

So it turns out that it throwed a Win32 related error locally which i get to fix using another version of the Win32 lib. So ghc-boot-9.2.1 seems to be the solution indeed 🤷

Well in any case it is clear it is not related with the lib itself, thanks again!