Add a code action provider for the eval plugin (existing code lens)

[michaelpj]

At the moment it's only a code lens, but it could be a code action too.

In lsp-mode this means it shows up when you explicitly show code lenses, but not in the sideline that shows code actions. So I actually thought it was broken (although arguably this just shows that I don't know lsp-mode well enough 😅).

[jmorag]

emacs-lsp/lsp-haskell#89

This also means that the eval plugin doesn't work with emacs lsp-mode

[michaelpj]

It does work, it just only works as a code lens. So you need to run lsp-lens-show to make the lenses show up. That's the way lsp-mode does code lenses vs code actions. Maybe we should open an issue there about improving the discoverability of code lenses.

[jmorag]

When I click the code lens, it doesn't insert the value of the evaluation, it just crashes with

(error "BadDependency "GhcSessionDeps"")
LSP :: Please open an issue in lsp-mode for implementing `21444:eval:evalCommand'.

@michaelpj does it insert the evaluation for you?

[michaelpj]

Yes, it works fine. I think you have a server issue that's unrelated to this one, I suggest opening another issue with the reproduction instructions.

[jneira]

There is other issue asking to have code lenses as code actions: #550

[michaelpj]

I think it would be nice if all code lens providers also provided equivalent code actions.

[jneira]

we could do it generically in hls-plugin-api, i hope