Coq LSP

The coq-lsp project aims to provide a lightweight, pure Language Server Protocol server implementation for the Coq proof assistant, as well as to serve as a framework for interface experimentation.

Warning: This project is at an early stage, and it has known bugs, see the issue tracker for more information.

Contributions are very welcome, but please first coordinate with the dev team in Zulip before writing any code, as the code evolves pretty quickly.

Development Channel

Our development channel can be found at Coq's Zulip, don't hesitate to stop by.

Installation

• coq-lsp server: opam install coq-lsp

Clients

• Visual Studio Code: https://marketplace.visualstudio.com/items?itemName=ejgallego.coq-lsp
• GNU Emacs: M-x eglot [Enter] coq-lsp [Enter]

FAQ

See our list of frequently-asked questions.

Troubleshooting

• Most problems can be resolved by restarting coq-lsp, in Visual Studio Code, Ctrl+Shift+P will give you access to the coq-lsp.restart command.
• In VSCode, the "Output" window will have a "Coq LSP Server Events" channel which should contain some important information.
• As of today, coq-lsp may have trouble when more than one file is open at the same time, this is a problem upstream. For now, you are advised to work on a single file if this problem appears.

Features

Incremental compilation and continuous document checking:

Edit your file, and coq-lsp will try to re-check only what is necessary, continuously. No more dreaded Ctrl-C Ctrl-N! Rechecking tries to be smart, and will ignore whitespace changes.

In a future release, coq-lsp will save its document cache to disk, so you can restart your proof session where you left it at the last time.

Incremental support is undergoing refinement, if coq-lsp rechecks when it should not, please file a bug!

Smart, Cache-aware Error recovery

coq-lsp won't stop checking on errors, but supports (and encourages) working with proof documents that are only partially working. Moreover, error recovery integrates with the incremental cache, and will recognize proof structure.

You can edit without fear inside a Proof. ... Qed., the rest of the document won't be rechecked, unless the proof is completed.

Whole-Document Goal Display

Press Alt+Enter (or Cmd+Enter in Mac) to show goals at point in a side panel.

Markdown support

Open a markdown file with a .mv extension, coq-lsp will check the code parts! coq-lsp places human-friendly documents at the core of its design ideas.

Document outline:

coq-lsp supports document outline and code folding, allowing you to jump directly to definitions in the document.

Detailed timing and memory stats

Hover over any Coq sentence, coq-lsp will display detailed memory and timing statistics.

Client-side configuration options

coq-lsp is configurable, and tries to adapt to your own workflow. What to do when a proof doesn't check, admit or ignore? You decide!

See the coq-lsp extension configuration in VSCode for options available.

Reusability, standards, modularity

The incremental document checking library of coq-lsp has been designed to be reusable by other projects written in OCaml and with needs for document validation UI, as well as by other Coq projects such as jsCoq.

Moreover, we are strongly based on standards, aiming for the least possible extensions.

A Platform for Research !

A key coq-lsp goal is to serve as central platform for researchers in Human-Computer-Interaction, Machine Learning, and Software Engineering willing to interact with Coq.

Towards this goal, coq-lsp extends and will eventually replace coq-serapi, which has been used by many to that purpose.

Planned features

Jump to definition

In progress, pending on coq/coq#16261

Proof skipping

Configure which proofs to skip or delay, to make your document workflow more reactive.

Contextual continuous checking

Check only what is visible, à la Isabelle.

Server-side Completion Help

"Semantic" goal and document printing

LaTeX document support

Workspace Integration

Don't worry about ever having to build your project again, coq-lsp will detect your workspace and build setup, and will keep everything up to date automatically.

Responsible elaboration and refinement

Supporting inlays and Lean-style info view.

"Computational", Jupyter-style Documents

Suggestions / Search panel

Protocol Notes

coq-lsp mostly implements the LSP Standard, plus some extensions specific to Coq.

Check the coq-lsp protocol documentation for more details.

Development / Building from sources

Server:

To build the server, you'll need and environment with the dependencies stated in coq-lsp.opam. Opam users can do opam install --deps-only ..

Once you have done that, do make, and the server will be build under _build/install/default/bin/

Nix

We have a Nix flake that you can use. For development, simply run nix develop.

If you wish to do nix build or compose this flake from another project, you will need to use the .?submodules=1` trick, since we use submodules here for vendoring. For example, building requires:

nix build .?submodules=1

You can use this flake in other flakes or Nix derviations.

Visual Studio Code:

Run npm install && npm run compile in editor/code.

(cd editor/code && npm i && npm run compile)

Now you can launch VS Code through dune exec -- code -n, this will setup the right environment variables such as PATH and OCAMLPATH.

Now, run the extension normally using the left "Run and Debug" panel in Visual Studio Code.

Emacs

You can use this mode with eglot with $path_to_server --std. Note that --std is needed otherwise eglot may choke due to extra messages.

Roadmap

For now the main focus of the project to write clean and maintainable code, and to provide a smooth user experience.

A core goal at this stage is to provide feedback upstream so the Coq API can be tailored to provide a good interactive experience.

For the planned first release, we hope to provide a reasonable implementation of core LSP features, editor support in VS Code.

Code organization

coq-lsp consists of several components:

• coq-serapi: [vendored] improved utility functions to handle Coq AST
• coq: Utility library / abstracted Coq API. This is the main entry point for communication with Coq.
• fleche: incremental document processing backend. Exposes a generic API, but closely modelled to match LSP methods
• lsp: small generic LSP utilities, at some point to be replaced by a generic lib
• controller: LSP controller, a thin layer translating LSP transport layer to flèche surface API.

Licensing information

The license for this project is LGPL 2.1 (or GPL 3+ as stated in the LGPL 2.1).

• This server forked from our previous LSP implementation in for the Lambdapi by Emilio J. Gallego Arias, Frédéric Blanqui, Rodolphe Lepigre, and others.

• Syntax files in editor/code are partially derived from VSCoq by Christian J. Bell, distributed under the terms of the MIT license (see ./vsc-galinas/License-vscoq.text).

Team

• Ali Caglayan (co-coordinator)
• Emilio J. Gallego Arias (Inria Paris, co-coordinator)
• Shachar Itzhaky (Technion)
• Ramkumar Ramachandra

Acknowledgments

Work on this server has been made possible thanks to many discussions, inspirations, and sharing of ideas from colleagues. In particular, we'd like to thank Rudi Grinberg, Andrey Mokhov, Clément Pit-Claudel, and Makarius Wenzel for their help and advice.

As noted above, the original implementation was based on the Lambdapi LSP server, thanks to all our collaborators in that project!