Implement the Language Server Protocol (LSP) for Dex

[apaszke]

The Language Server Protocol (LSP) is a protocol used between languages and IDE-like tools to provide language-aware IDE features, like jump-to-definition, find-all-references, and code completion.

It would be great for Dex to have LSP support: this could be used to implement a Visual Studio Code extension or Emacs mode for Dex, or to augment dex web <file.dx> with language-aware features like hover tooltips showing the types of variables and all references of a variable.

We're brainstorming some grander ideas for redesigning the Dex compiler to be more query-evaluation-oriented and API-oriented, and an LSP implementation overlaps with that vision. There's more design work and discussion to do, so we're not ready to start any implementation yet.

References

• Language Server Protocol homepage: overview, specification, and implementations
• haskell-lsp library: for implementing LSP for languages written in Haskell
• Draft LSP implementation for the Koka language via haskell-lsp: <1000 lines in changes

Originally posted by @dan-zheng in #375

[general-rishkin]

What is the status of the LSP?
Is there a temporary alternative in the meantime, e.g., for vim or gedit, etc?

[apaszke]

@sharadmv wrote dex-vim, but it only does syntax highlighting

[general-rishkin]

Excellent. That something at least. Thanks.

[dan-zheng]

Subsumed by #1304: adding tooltips to dex web.