Butter Language (VS Code)

Editor support for .butter files: TextMate-grammar syntax highlighting (derived from GRAMMAR.bnf's lexical rules) plus a language client that starts butter-lsp — the Butter language server — for diagnostics, hover, go-to-definition, document outline, and completion.

Language Server

The extension's src/extension.ts starts butter-lsp as a child process and talks LSP to it over stdio; all of the actual language intelligence lives there, built on the same lexer/parser/module-loader/compiler butter itself uses (src/lsp/ in the repo root).

Marketplace installs: a prebuilt butter-lsp for your platform ships inside the extension (see Package as a .vsix below) — nothing to build or install separately, and no other configuration is needed.

Building from source / overriding the version, one of two ways (from the repo root, requires Zig 0.16.0):

zig build

This produces zig-out/bin/butter-lsp (butter-lsp.exe on Windows) alongside the butter CLI itself. Then either:

• Put it on your PATH — used as a fallback if no bundled binary is found (e.g. running the extension unpackaged via F5).
• Or set the butter.lsp.path setting to its full path, which always takes priority over both the bundled binary and PATH.

Features (this pass): diagnostics (parse and semantic errors, live as you type, across imported files too), hover (declared function/struct/enum/ variable signatures — not fully inferred expression types), go-to- definition (same-file, across imports, and into the bundled stdlib), document outline, and context-aware completion (keywords, in-scope locals, same-file and imported symbols, struct fields/methods after expr., enum variants after EnumName.).

Try it locally

From this folder, either:

• Press F5 in VS Code (with this folder open) to launch an Extension Development Host with the grammar and language client loaded, or
• Symlink/copy this folder into your VS Code extensions directory (%USERPROFILE%\.vscode\extensions\butter-language on Windows) and restart VS Code.

Either way, first install the client's own dependencies and build it:

npm install
npm run compile

Package as a .vsix

Each platform gets its own .vsix with that platform's butter-lsp binary bundled in under bin/. From the repo root, build the release binaries once (cross-compiles all targets from any host):

zig build release

Then, from this folder:

npm install
npm run package:win32-x64    # or :linux-x64, :linux-arm64, :darwin-x64, :darwin-arm64
npm run package:all          # all five at once

Each stages the matching zig-out/release/<triple>/butter-lsp(.exe) into bin/ (via scripts/stage-lsp-binary.js) before invoking vsce package --target <platform>. Install one to test: code --install-extension butter-language-<version>-<target>.vsix.

For quick local testing without picking a target, npm run package stages the host platform's binary and produces a single untargeted .vsix.

Publishing (vsce login zbutter with a Marketplace personal access token, then npm run publish:all or npm run publish:<target>) is a manual step — it's the Marketplace publisher's own credential and isn't part of this build.