Migrate to OsPath

[kokobd]

We have a better alternative to FilePath now. See: https://hasufell.github.io/posts/2022-06-29-fixing-haskell-filepaths.html

What we should do:

1. Change NormalizedFilePath to NormalizedOsPath after the issue in lsp to support OsPath Migrate to OsPath lsp#445 is solved. Profiling it to make sure the performance improves.
2. Change other usages of FilePath to OsPath

However, this can not be done until ghc-9.6 is released (ships the new filepath library), or all ghc shipped libraries are available on Hackage.

Many GHC bundled libraries do not have new versions released to Hackage (for example ghci and hpc, their versions on hackage is very old). Thus, cabal solver fails if I add filepath ^>= 1.4.100.0 to a project that depends on ghc, which then depends on ghci. The installed ghci links against filepath-1.4.2.2 in this case, and cabal can not rebuild a ghci with filepath ^>= 1.4.100.0, as the source code is not found on hackage.

[pepeiborra]

Thus, cabal solver fails if I add filepath ^>= 1.4.100.0 to a project that depends on ghc, which then depends on ghci.

Oh bummer. Well, if we really want to, it should be ok to embed OsPath and combinators in a filepath-compat package.

[hasufell]

https://gitlab.haskell.org/ghc/ghc/-/issues/21887#note_443922

It may be possible to provide updated GHC releases that include new filepath. But this is still in discussion.

[kokobd]

I don't know why, but the overall memory usage decreased from 1.5G to 700M
The data is collected by launching haskell-language-server from the command line in the HLS source repo with profiling RTS options enabled.

[hasufell]

@kokobd you mean between String and OsPath?

[kokobd]

@kokobd you mean between String and OsPath?

@hasufell Yes. But when loading HLS executable into VSCode, I no longer witness such a big difference. I'm still investigating the reason.

[pepeiborra]

Can you run cabal bench ghcide and share the contents of the ghcide/bench-results folder minus the binaries ?

[kokobd]

cabal bench ghcide is failing with master & ghc 9.2.3. Verified by creating a fresh new Gitpod workspace from master.

[pepeiborra]

I'll take a look, but in the meantime CI shows that it works fine on 8.10.7. Would you be able to run it there?

EDIT: nevermind, I see that 8.10.7 won't do
EDIT2: #3069 should help

[pepeiborra]

Ran the edit benchmark on Cabal 3.6.3.0, results seem quite promising: