rumdl — ZedExt

zed-rumdl

Zed extension for rumdl - a fast Markdown linter and formatter written in Rust.

Features

Real-time Markdown linting with inline diagnostics
Format on save and on-demand formatting
Automatic binary management (downloads rumdl automatically)
Respects project configuration (.rumdl.toml, pyproject.toml)
Configurable via Zed's LSP settings

Installation

Open Zed
Open the Extensions panel (cmd+shift+x on macOS)
Search for "rumdl"
Click Install

The extension will automatically download the appropriate rumdl binary for your platform.

Configuration

Zed Settings

rumdl starts automatically for Markdown files once the extension is installed. To format with rumdl, set it as the formatter explicitly. Zed's default ("formatter": "auto") formats Markdown with its built-in Prettier integration, so without this setting Prettier formats your files, not rumdl:

{
  "languages": {
    "Markdown": {
      "formatter": {
        "language_server": {
          "name": "rumdl"
        }
      },
      "format_on_save": "on"
    }
  }
}

If you set language_servers explicitly, keep the "..." placeholder so other language servers stay enabled alongside rumdl:

{
  "languages": {
    "Markdown": {
      "language_servers": ["rumdl", "..."]
    }
  }
}

Custom Binary Path

If you want to use a specific rumdl binary instead of the auto-downloaded one, you can also pass custom arguments (for example rumdl's global --config flag) and environment variables:

{
  "lsp": {
    "rumdl": {
      "binary": {
        "path": "/path/to/rumdl",
        "arguments": ["server", "--config", "/path/to/.rumdl.toml"],
        "env": {
          "RUMDL_LOG": "debug"
        }
      }
    }
  }
}

When setting a custom path, always include "arguments": ["server"]: Zed launches a settings-configured binary with exactly the arguments given and does not add the server subcommand itself, so without them rumdl starts in CLI mode and the language server fails. env entries are added to the server's environment. A configured path takes precedence over rumdl on your PATH, which in turn takes precedence over the auto-downloaded binary. Changes apply on the next language server restart, no Zed restart needed.

LSP Settings

You can pass configuration to rumdl via Zed's LSP settings. The shape matches rumdl's LSP configuration: server options at the top level (camelCase), rule configuration nested under settings:

{
  "lsp": {
    "rumdl": {
      "settings": {
        "configPath": ".rumdl.toml",
        "enableAutoFix": true,
        "settings": {
          "lineLength": 120,
          "disable": ["MD033"],
          "MD013": {
            "lineLength": 120
          }
        }
      }
    }
  }
}

These are sent to rumdl both as initialize options and on workspace/didChangeConfiguration, so edits apply without restarting the server. To send a different payload at initialization, set lsp.rumdl.initialization_options, which takes precedence over settings for the initialize request.

Using a System-Installed rumdl

If you have rumdl installed via Homebrew, Cargo, or another method, the extension will use that instead of downloading:

# Install via Homebrew
brew install rvben/tap/rumdl

# Or via Cargo
cargo install rumdl

# Or via mise
mise use rumdl@latest

Project Configuration

rumdl reads configuration from:

.rumdl.toml in your project root
pyproject.toml under [tool.rumdl]

See the rumdl documentation for all configuration options.

Troubleshooting

Extension not working

Check logs: Open the command palette and run zed: open log. Look for lines containing "rumdl".
Verify rumdl is installed: If using a system installation, verify with:
```
which rumdl
rumdl --version
```
Restart the language server: After installing or upgrading rumdl, run editor: restart language server from the command palette (or restart Zed) to pick up the new binary.

Diagnostics not showing

Check language server is enabled: rumdl is enabled by default for Markdown. If you override language_servers in your settings, make sure the list includes "rumdl".
Check file type: Ensure the file is recognized as Markdown (check the language indicator in the status bar).
Check rumdl configuration: Some rules may be disabled in your .rumdl.toml.

Format on save not working

Set rumdl as the formatter and enable format on save:

{
  "languages": {
    "Markdown": {
      "formatter": {
        "language_server": {
          "name": "rumdl"
        }
      },
      "format_on_save": "on"
    }
  }
}

Without the formatter setting, Zed formats Markdown with its built-in Prettier integration instead of rumdl.

Check if rumdl supports fixing the issue: Not all lint warnings have auto-fixes. Run rumdl check --fix to apply the fixes rumdl can make automatically.

Wrong rumdl version

The extension checks for rumdl in this order:

Custom binary path from LSP settings
System PATH (which rumdl)
Auto-downloaded from GitHub releases

To use a specific version, either:

Set a custom binary path in LSP settings
Ensure your preferred version is first in PATH
Remove any cached downloads (in Zed's extension data directory)

Settings and PATH are re-checked every time the language server starts, so switching binaries only needs editor: restart language server, not a Zed restart. If GitHub is unreachable, the extension falls back to the most recently downloaded binary.

Requirements

Zed editor
macOS (Intel or Apple Silicon), Linux (x86_64 or ARM64), or Windows (x86_64)

Contributing

Contributions are welcome! Please see the issue templates for reporting bugs or requesting features.

For issues with rumdl's linting rules or CLI, please use the main rumdl repository.

License

MIT