Follow definitions across local packages

[JosephLucas]

Does ghcide plan to implement a feature to follow definitions across local packages ? That would be really helpful for projects built with obelisk (reflex-frp).

[cocreature]

In principle we have the logic for that already if there are .hie files for dependencies. But to make it usable for Haskell (we use it for DAML) there are however a few open questions here:

1. How do we locate .hie files for a dependency?
2. How do we locate source files for a dependency?
3. Do we want to load the source file of a dependency? If so, which flags do we use?

I think 1 and 2 probably need to come from hie-bios since that is definitely specific to each build tool. For 3 I don’t really have a great answer. At least initially the most sensible solution seems to be to just not load the source file at least not unless it’s a “local” package (e.g. for cabal that would mean that it’s listed in packagesin cabal.project).

[jneira]

I've just checked this one in haskell-lsp and it is not implemented yet.
I guess @wz1000 work about using a database to store the needed info could enable this

[jneira]

Hi, i've tested it out again with haskell-lsp and haskell-lsp-types and it works. However you must open a file from the dependant package (haskell-lsp-types in this case) before being able to jump from the dependent package (haskell-lsp).
@JosephLucas could you try in that order to check if it works for you?

[JosephLucas]

No success with ob init, ob shell, vscode with haskell plugin.

I also tried to write a minimal multi-project setup, but the feature does not work and I get this error:

Failed to parse result of calling cabal
Resolving dependencies...

Warning: The package list for 'hackage.haskell.org' is 148 days old.
Run 'cabal update' to get the latest list of available packages.
cabal: Could not resolve dependencies:
[__0] trying: B-0.0.0 (user goal)
[__1] unknown package: p1 (dependency of B)
[__1] fail (backjumping, conflict set: B, p1)
After searching the rest of the dependency tree exhaustively, these were the
goals I've had most trouble fulfilling: B, p1

Since I am a bit lost in the haskell packaging, it is very probable that my fixture is wrong though.

---

Steps to reproduce my attempt:

1. Download, decompress, and cd into, the attached fixture folder minimal_fixture_multi_projects.zip

2. use a shell env with cabal v3, ghc 8.8.4 and appropriate packages thanks to shell.nix using the unstable tested branch

nix-shell

3. Use the haskell plugin of vscode (default config).

[jneira]

@JosephLucas i am not using nix, but i will try to reproduce in my env with that zip

[jneira]

With the inclusion of hiedb go to definition has been improved (see #704)
@JosephLucas had you the opportunity of thrying hls-1.0 to see if it fixes the issue for you?

[JosephLucas]

I just did it with my fixture and I keep getting the same error, while using haskell-language-server-1.0.0-linux-8.6.5.