Weird behaviour with loading custom GHCI config

[georgefst]

This is with cabal-install 3.6.2.0, GHC 8.10.7, Manjaro Linux.

I have the following in my ~/.ghc/ghci.conf:

:add /home/gthomas/.ghc/ghci.hs
:set -interactive-print ghciInteractivePrint
:set prompt-function ghciPromptFunction

And in ~/.ghc/ghci.hs (obviously this isn't my real config, it's much simplified):

ghciInteractivePrint :: Show a => a -> IO ()
ghciInteractivePrint x = putStrLn "printing..."

ghciPromptFunction :: [String] -> Int -> IO String
ghciPromptFunction modules _lineno = pure "prompt> "

In plain ghci, everything works as expected:

GHCi, version 8.10.7: https://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling Main             ( /home/gthomas/.ghc/ghci.hs, interpreted )
Ok, one module loaded.
Loaded GHCi configuration from /home/gthomas/.ghc/ghci.conf
prompt> 1
printing...
prompt>

Running cabal repl within a cabal project directory, somehow ghciPromptFunction is loaded but not ghciInteractivePrint:

Build profile: -w ghc-8.10.7 -O1
In order, the following will be built (use -v for more details):
 - hello-hs-0.1.0.0 (exe:hello-hs) (file app/Main.hs changed)
Preprocessing executable 'hello-hs' for hello-hs-0.1.0.0..
GHCi, version 8.10.7: https://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling Main             ( /home/gthomas/.ghc/ghci.hs, interpreted )
Ok, one module loaded.
Loaded GHCi configuration from /home/gthomas/.ghc/ghci.conf
[1 of 1] Compiling Main             ( app/Main.hs, interpreted )
Ok, one module loaded.
prompt> 1
1
prompt>

Running cabal repl outside of a project directory, everything fails to load, but there are at least visible errors (possibly only due to setcwd.ghci, which I can't find any mention of anywhere - what's the purpose of it?):

Resolving dependencies...
Build profile: -w ghc-8.10.7 -O1
In order, the following will be built (use -v for more details):
 - fake-package-0 (lib) (first run)
Configuring library for fake-package-0..
Preprocessing library for fake-package-0..
Warning: No exposed modules
GHCi, version 8.10.7: https://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling Main             ( /home/gthomas/.ghc/ghci.hs, interpreted )
Ok, one module loaded.

<interactive>:1:1: error: Not in scope: ‘ghciInteractivePrint’

<interactive>:1:2: error:
    Variable not in scope:
      ghciPromptFunction :: [String] -> Int -> IO String
Loaded GHCi configuration from /home/gthomas/.ghc/ghci.conf
Warning: changing directory causes all loaded modules to be unloaded,
because the search path has changed.
Loaded GHCi configuration from /tmp/cabal-repl.-171000/setcwd.ghci
Prelude> 1
1
Prelude>

[fgaz]

Thanks for the bug report.

The second case can be explained by

Warning: changing directory causes all loaded modules to be unloaded,
because the search path has changed.
Loaded GHCi configuration from /tmp/cabal-repl.-171000/setcwd.ghci

setcwd.ghci is a configuration file generated by cabal repl that sets the working directory to a dummy temporary project (related: #6977). it may be that it causes /home/gthomas/.ghc/ghci.hs to be unloaded too.

---

i get a different but still problematic output in the project case

[...]
[1 of 1] Compiling Main             ( /home/fgaz/.ghc/ghci.hs, interpreted )
Ok, one module loaded.

<interactive>:1:1: error: Not in scope: ‘ghciInteractivePrint’

<interactive>:1:2: error:
    Variable not in scope:
      ghciPromptFunction :: [String] -> Int -> IO String
Loaded GHCi configuration from /home/fgaz/.ghc/ghci.conf
[...]

Weird indeed!

[georgefst]

Ah, so presumably without setcwd.ghci, we'd end up in /tmp or something? Oh well, all the more reason to look forward to the removal of fake-package.

The in-project case is the one I'm more interested in anyway.

[jneira]

#1471 suggested to directly make cabal don load .ghci, but it seems that does not fit all workflows so it would need at least a flag