MoonBit Community

MoonBit language support for the Zed editor.

This extension provides Tree-sitter-based syntax highlighting and integrates the MoonBit Language Server (moonbit-lsp).

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Features

• Syntax highlighting (Tree-sitter)
• MoonBit 0.10 grammar and syntax coverage
• LSP integration (moonbit-lsp)
• Outline support (basic)
• Brackets + indentation

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Status

Early-stage but functional.

The main focus is correctness of Tree-sitter queries. Coverage is intentionally minimal and will evolve with the upstream MoonBit grammar.

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Requirements

• Zed Editor
• moonbit-lsp in PATH
• Rust toolchain (for dev only)

Install LSP:

npm install -g @moonbit/moonbit-lsp

Verify:

which moonbit-lsp

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Installation (Dev)

Clone:

git clone https://github.com/Metalymph/zed-moonbit
cd zed-moonbit

In Zed:

• open command palette
• run: zed: install dev extension

Note: For the official releases look at Releases.

Optional: associate moon.pkg with MoonBit

Since moon.pkg is a MoonBit package manifest rather than a .mbt source file, you may want to associate it manually in Zed settings:

{
  "file_types": {
    "MoonBit": ["moon.pkg"]
  }
}

Zed currently does not support matching exact filenames in language extensions, so this must be configured manually.

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Development Workflow

Core commands

Using Just:

just dev
just validate-queries
just test-syntax
just zed-log

Using Make:

make dev
make validate-queries
make test-syntax
make zed-log

Windows (PowerShell):

pwsh -File scripts/dev.ps1

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What dev does

• validates Tree-sitter queries
• prints Zed log path
• opens project in Zed

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Tree-sitter Development

All syntax behavior is driven by:

languages/moonbit/*.scm

You must not guess node names.

Use:

make validate-queries

or:

just validate-queries

If queries are invalid, Zed will fail to load the language.

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Debugging

Show log path:

just zed-log-path

Tail logs:

just zed-log

Common error:

Invalid node type "..."

Fix by checking:

tree-sitter parse file.mbt

and:

src/node-types.json

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Project Structure

src/lib.rs                -> Rust extension entry point
extension.toml           -> extension manifest
languages/moonbit/       -> Tree-sitter config + queries
scripts/                 -> validation + dev tools

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Design Principles

• minimal queries > complex broken queries
• no guessed AST nodes
• validate before testing
• keep extension logic thin (LSP does the heavy work)

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Roadmap

• improve query coverage
• refine outline support
• stabilize indentation rules
• prepare for extension registry release

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Contributing

Small, focused changes only.

Before opening a PR:

make validate-queries

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Troubleshooting

Generally speaking, if you meet any problem, open an issue on GitHub.

Error: failed to compile grammar 'moonbit'

If you see this error while installing the extension, it may be caused by a corrupted or conflicting local grammar cache in Zed.

Zed clones the Tree-sitter grammar into a local grammars/moonbit directory. If that folder already exists but is not a valid Git repository (or does not match the expected remote), installation can fail.

Fix:

1. Locate Zed’s extensions/grammars directory (depends on your OS).
2. Delete the grammars folder (or at least grammars/moonbit).
3. Restart Zed.
4. Reinstall the extension.

This is a local state issue and not a problem with the extension itself.

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License

MIT