package coq-lsp

Coq LSP

coq-lsp is a Language Server and Visual Studio Code extension for the Coq Proof Assistant.

Key features of coq-lsp are continuous and incremental document checking, advanced error recovery, markdown support, positional goals and information panel, performance data, and more.

coq-lsp aims to provide a seamless, modern interactive theorem proving experience, as well as to serve as a platform for research and UI integration with other projects.

Installation

In order to use coq-lsp you'll need to install both the coq-lsp server, and the Visual Studio Code extension:

Server

• opam: opam install coq-lsp
• Nix (coming soon)
• Coq Platform (coming soon)
• Do it yourself!

Visual Studio Code:

• Official Marketplace: https://marketplace.visualstudio.com/items?itemName=ejgallego.coq-lsp
• Open VSX: https://open-vsx.org/extension/ejgallego/coq-lsp

FAQ

See our list of frequently-asked questions.

Contributing

Contributions are very welcome! Feel free to chat with the dev team in Zulip, or just use the standard GitHub facilities. We will soon publish a thing of interesting projects for coq-lsp in case you are looking for ideas.

Development Channel

coq-lsp development channel it at Coq's Zulip, don't hesitate to stop by.

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.
• If you install coq-lsp simultaneously with VSCoq, VSCode gets confused and neither of them will work. Help with resolving this issue is extremely appreciated!

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

See planned features and contribution ideas for a list of things we plan to do, and tasks that you could take over.

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.

make will build the server at _build/install/default/bin/coq-lsp

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:

There are two ways to work with the VS Code extension: you can let VS Code itself take care of building it (preferred setup), or you can build it manually.

First, run npm install in editor/code:

(cd editor/code && npm i)

That will setup the required packages as it is usual. You can run package.json scripts the usual way:

(cd editor/code && npm run typecheck) # typecheck the project
(cd editor/code && npm run compile) # fast dev-transpile (no typecheck)

If you want to work with VS Code, these commands are not necessary, VS Code will build the project automatically.

Launch VS Code using dune exec -- code -n editor/code, which will setup the right environment variables such as PATH and OCAMLPATH, so the coq-lsp binary can be found by VS Code. If you have installed coq-lsp globally, you don't need dune exec, and can just run code -n editor/code.

Once in VS Code, you can launch the extension normally using the left "Run and Debug" panel in Visual Studio Code, or the F5 keybinding.

You can of course install the extension in your ~/.vscode/ folder if so you desire.

Emacs

You can use coq-lsp with eglot.

If you find any trouble using eglot or lsp-mode with coq-lsp, please don't hesitate to open an issue, Emacs support is a goal of coq-lsp.

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!