Re: Cabal woe

I think Simon has a point. I really do not enjoy creating a new throwaway project for every small reproducer I want to test.

My (clearly faulty) mental model is this. - I have a particular stage2 compiler, say $(GHC). Maybe built in my build tree, maybe installed. - If I say `$(GHC) -package primitive`, it right says "I don't know about primitiver" - I expect to be able to say `cabal install primitive --with-compiler=$(GHC)`, to extend my $(GHC) with the package `primitive`. - Thereafter I expect `$(GHC) -package primitive` to work -- after all, I have extended GHC to know about it. If I'm in a cabal project then these installed-by-default packages shouldn't make any difference; cabal will control everything. I'm sure it used to be like this, but something has changed, and I'm not sure why. Clearly my model of cabal is faulty, but I don't know how to get an accurate one. Is there a writeup I can read? e.g. What is the "environments" file? Why does it fail to find Prelude? Would it be possible to support the simple story above, as well? Simon On Tue, 9 Jul 2024 at 13:23, Sebastian Graf wrote:

Hi Simon, Hi Matt,

I think Simon has a point. I really do not enjoy creating a new throwaway project for every small reproducer I want to test. A cabal project means that I can't simply pass `-fforce-recomp -ddump-simpl -O` to a GHC invocation, for example. Instead I have to create a cabal file and remember all the fields that need to be set. (Or <enter> myself through a perceived 30 step wizard with `cabal new`, only to find that I have to open the file anyway to tweak build-depends...)

Stupid as it may be, that subconsciously really affects my willingness to tackle an issue.

Presumably this can be solved through some amount of automation/scripting. Perhaps it would be enough to share these scripts in a prominent location, for example the Wiki. Alternatively, I think I would enjoy something like `nix-shell -p`, where I can just fire up a temporary shell with all the deps in a locally visible package db. That way I could keep calling `ghc` directly.

(Not that I suffer *much* from this issue at the moment anyway.)

Sebastian

Am Di., 9. Juli 2024 um 11:21 Uhr schrieb Matthew Pickering < matthewtpickering@gmail.com>:

...

`cabal install --lib` is very hard to use properly. I would advise against it.

It is much easier to create a simple cabal project and use normal cabal build commands. I packaged things in a repo for you.

https://github.com/mpickering/t25064

``` cabal build -w ghc-9.6.2 (fails) cabal build -w /path/to/devel/compiler (fails with error message) ```

Matt

On Tue, Jul 9, 2024 at 9:58 AM Simon Peyton Jones wrote:

...

Friends

I'm trying to repro #25064 with my development build of GHC. The test

case depends on packages `primitive` and `hashtables`. So I try this (see below).

...

Alas, apparently after the `cabal install`, it can't find Prelude.

What should I do? I tried removing the "environments" file, whatever

that is, which then meant it could find Prelude -- but the libraries were no longer installed.

...

I lack a decent model of what is going on with installing packages for

my development builds. Is there a write up anywhere?

...

Thanks

Simon

bash$ cabal install --lib hashtables primitive --with-compiler

$HOME/code/HEAD/$s2

...

Warning: Unknown/unsupported 'ghc' version detected (Cabal 3.10.1.0 supports 'ghc' version < 9.8): /home/simonpj/code/HEAD/_build/stage1/bin/ghc is version 9.11.20240517 Warning: Unknown/unsupported 'ghc' version detected (Cabal 3.10.1.0 supports 'ghc' version < 9.8): /home/simonpj/code/HEAD/_build/stage1/bin/ghc is version 9.11.20240517 Resolving dependencies... bash$ ~/code/HEAD/$s2 -c T25064.hs Loaded package environment from T25064.hs:1:8: error: [ ]8;; https://errors.haskell.org/messages/GHC-87110 \GHC-87110 ]8;; \] Could not load module ‘Prelude’. It is a member of the hidden package ‘base-4.20.0.0’. Use -v to see a list of the files searched for. | 1 | module Bug where | ^^^

bash$ rm /home/simonpj/.ghc/x86_64-linux-9.11.20240517/environments/default bash$ ~/code/HEAD/$s2 -c T25064.hs T25064.hs:3:1: error: [ ]8;; https://errors.haskell.org/messages/GHC-61948 \GHC-61948 ]8;; \] Could not find module ‘Control.Monad.Primitive’. Perhaps you meant Control.Monad.Writer (from mtl-2.3.1) Use -v to see a list of the files searched for. | 3 | import Control.Monad.Primitive | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

T25064.hs:4:1: error: [ ]8;; https://errors.haskell.org/messages/GHC-87110 \GHC-87110 ]8;; \] Could not find module ‘Data.HashTable.ST.Basic’. Use -v to see a list of the files searched for. | 4 | import qualified Data.HashTable.ST.Basic as H | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

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