Haskell-ide-engine: Full debugger support

[vavans]

I think we need a way to get access to main debugger features for a given program. I know the ghci debbuger but it would be nice if it could be run by a public API
An API wich provides:

• [ ] set a breakpoint (classic and conditional)
• [ ] step by step
• [ ] step into function
• [ ] step outside function
• [ ] watch a binding
• [ ] force evaluation
• [ ] current call stack visualization and exploration

You can have a good overview of IDE needs by looking at the VSCode debuging protocol:
https://github.com/Microsoft/vscode-debugadapter-node/blob/master/protocol/src/debugProtocol.ts

With more general explanation here:
https://code.visualstudio.com/docs/extensionAPI/api-debugging

[mgsloan]

ide-backend's debugger support never got very sophisticated, but it may be helpful to reference https://github.com/fpco/ide-backend/blob/master/ide-backend-server/Run.hs#L413

[alanz]

I've actually been looking at the vscode/omnisharp protocol again, with a view to building a HIE transport for it. Which brings in all the omnisharp-capable IDEs at one fell swoop.

[rvion]

Phoityne meets most some of above requirements

https://hackage.haskell.org/package/phoityne-vscode
https://marketplace.visualstudio.com/items?itemName=phoityne.phoityne-vscode

edit:

from readme:

supportsConfigurationDoneRequest : yes
supportsFunctionBreakpoints : yes
supportsConditionalBreakpoints : yes
supportsEvaluateForHovers : yes
exceptionBreakpointFilters : no
supportsStepBack : no
supportsSetVariable : no
supportsRestartFrame : no
supportsGotoTargetsRequest : no
supportsStepInTargetsRequest : no
supportsCompletionsRequest : yes

[nponeccop]

Some information from LSP4E (Eclipse LSP Client project): https://github.com/eclipse/lsp4j/issues/130

[alanz]

The Phoityne debugger uses this at the back https://hackage.haskell.org/package/haskell-dap which implements the vscode debug protocal, as I understand it.

Using a standard protocol makes sense to me, but it is not as widely implemented as LSP. See https://code.visualstudio.com/docs/extensionAPI/api-debugging

And there is a ticket asking for LSP4J support, it is a complex ecosystem.

[spacekitteh]

Any update on this?

[jneira]

more useful links:

• Prior job, debug support for atom editor using ghci executable: https://github.com/atom-haskell/haskell-debug
• Original paper: https://simonmar.github.io/bib/papers/ghci-debug.pdf
• ghc reference about debugger: https://downloads.haskell.org/ghc/latest/docs/html/users_guide/ghci.html#the-ghci-debugger

[alanz]

The standard is now DAP, I would say, supported in both emacs and vscode.

And as I said earlier, phoityne already supports it, maybe we should consider an integration with it.

Fundamentally this is about having a GHCI session at the same time, which has been considered quite a bit. See e.g https://gitlab.haskell.org/ghc/ghc/issues/15461