croma ABC

croma ABC — Zed extension

Native ABC music notation support for the Zed editor: syntax highlighting, code folding, and bracket matching via the in-repo tree-sitter-abc grammar, plus diagnostics / formatting / hover / completion / symbols by launching the croma-lsp language server.

Zed = GPUI, the same engine as croma's GPUI app. This extension is also a real-engine smoke test of croma-lsp.

What you get

• Syntax highlighting — pitches, accidentals, lengths, rests, tuplets, barlines/repeats, slurs/ties, chord symbols, annotations, decorations, header fields, inline fields, comments, and %% stylesheet directives.
• Folding — fold a whole tune, just its body, or just its header.
• Bracket matching — chord [ … ] and grace { … } groups, quoted strings.
• Language server — everything croma-lsp provides over stdio (diagnostics, formatting, semantic tokens, document symbols, folding ranges, hover, completion, code actions).

Files with the .abc suffix are recognized as the ABC language.

Prerequisites: the croma-lsp binary

The extension resolves the language server with a download-or-PATH strategy:

1. croma-lsp on your PATH (works today):

   # from a croma checkout
   cargo install --path crates/croma-lsp
   

   This installs croma-lsp into ~/.cargo/bin; make sure that is on your PATH. Once croma-lsp is published you will be able to cargo install croma-lsp.

2. Automatic GitHub-release download — when croma cuts binary releases, the extension downloads the right croma-lsp for your platform automatically. No manual install needed. (Not yet functional — pending the release epic.)

3. Otherwise the extension shows a clear error pointing you back at step 1.

Dev-installing the extension in Zed

This extension is not yet published to the Zed extension registry, so install it as a dev extension:

1. Build / install croma-lsp so it is on your PATH (see above).
2. In Zed, open the command palette and run zed: install dev extension.
3. Select this directory (editors/zed/).

Zed compiles the extension to WebAssembly, builds the grammar, and registers the ABC language. Open any .abc file to verify highlighting; the status bar should show the croma-lsp language server attaching.

The grammar is wired by repository + monorepo path (tree-sitter-abc), which requires a reasonably recent Zed that supports the path key in [grammars.*].

Building / testing the extension crate directly

This crate (zed_croma_abc) is intentionally excluded from the croma cargo workspace (it targets wasm and pulls in zed_extension_api). Build and test it from this directory:

# compile to the wasm target Zed loads
cargo build --release --target wasm32-wasip1

# run the host-side unit tests (the pure release-asset-name resolver)
cargo test

# lint / format
cargo clippy --all-targets -- -D warnings
cargo fmt --check

Layout

editors/zed/
├── extension.toml          # extension manifest: grammar pin + croma-lsp server
├── Cargo.toml              # wasm extension crate (excluded from the workspace)
├── src/lib.rs              # Extension impl + download-or-PATH resolver
└── languages/abc/
    ├── config.toml         # name/suffix/comments/brackets/autoclose
    ├── highlights.scm      # Zed copies of the canonical grammar queries,
    ├── folds.scm           #   kept in sync with tree-sitter-abc/queries/*
    └── brackets.scm