feat(lsp): Language Server Protocol (LSP)

[mmsaki]

Motivation

This PR introduces native Language Server Protocol (LSP) support to Foundry via a new forge lsp command.

The motivation behind this is to provide a first-class developer experience for Solidity projects using Foundry by exposing core compiler features (like linting, syntax errors, remappings, etc.) directly to LSP-compatible editors such as Neovim and VSCode.

Previously, users had to rely on external plugins or custom tooling to get real-time feedback while editing Solidity code. This native integration unlocks accurate diagnostics, contextual tooling, and seamless integration with Forge projects out of the box.

Solution

This PR adds:

• A new command: forge lsp
• A tokio-based LSP server implementation using tower-lsp
• The server is implemented in crates/lsp, and registered as a new Forge subcommand.
• Designed for extensibility: future support for hover, and code actions is planned.
• Initial support for forge lint notification via "textDocument/publishDiagnostics" requests with streaming updates

PR Checklist

• Added Tests
• Added Documentation

Done

• forge build errors & warnigns
• forge lint diagnostics
• textDocument/definition
• textDocument/declaration

Planned

• textDocument/rename
• textDocument/formatting
• Hover information
• Symbol search and references
• Code completion
• Code Actions

[0xClandestine]

Thanks for carrying the torch on this, I have wanted a solid LSP for what feels like ages. The fact that forge lint is built-in is the cherry on top, well done brother.

[mmsaki]

Thanks for carrying the torch on this, I have wanted a solid LSP for what feels like ages. The fact that forge lint built-in is the cherry on top, well done brother.

It's so underrated. Already used the LSP to remove 84 unused imports in uniswap v4-core 👀 see PR Uniswap/v4-core#979, refactoring 45 files really easy with the LSP even without all the other features.

@0xClandestine Thanks for your work on forge lint too.

[0xClandestine]

@mmsaki Lol, I had a similar PR the other day forge lint is putting in work.

This actually solves one of my main frustrations when running forge lint on larger repos, the output is super noisy without filtering. With forge lsp you can simply navigate to your desired file and hover over concerning highlights.

Anyways, I was able to get it to work with vscode (and cursor) using the following extension and config if others are interested in trying it out:

[
  {
    "languageId": "solidity",
    "command": "forge",
    "fileExtensions": [
      ".sol"
    ],
    "args": [
      "lsp"
    ]
  }
]

[mmsaki]

@0xClandestine Thanks for testing it on vscode! Looks amazing 🙌.

[DaniPopes]

Hi, thanks for your contribution. We would like to hold off on this for the moment as we have plans of implementing it upstream in solar. In this current state it won't work well for large projects, but we will certainly integrate parts of this PR upstream.

[mmsaki]

Happy to see this getting pick up upstream! LFG 🙌