smelt VSCode Extension

Language support for smelt (Modern data transformation framework) data pipeline models.

Features

• Syntax Highlighting: Highlights SQL keywords and smelt template syntax ({{ ref() }}, {{ config() }})
• Diagnostics: Shows errors for undefined model references
• Go to Definition: Ctrl+Click (Cmd+Click on Mac) on {{ ref('model_name') }} to jump to the model definition
• Incremental Updates: Fast feedback powered by Salsa incremental compilation

Requirements

• Rust toolchain: Required to build the language server
• sqt project: The extension activates when it detects a workspace with models/*.sql files

Installation

Option 1: Install from VSIX (Recommended for testing)

1. Build the extension:

   cd editors/vscode
   npm install
   npm run compile
   npm run package
   

2. Install the generated .vsix file in VSCode:

   • Open VSCode
   • Go to Extensions view (Cmd+Shift+X)
   • Click "..." menu → "Install from VSIX..."
   • Select sqt-0.1.0.vsix

Option 2: Development Mode

1. Install dependencies:

   cd editors/vscode
   npm install
   

2. Open the editors/vscode folder in VSCode

3. Press F5 to launch Extension Development Host

4. Open a workspace containing smelt models

Usage

Project Structure

Your smelt project should have this structure:

my-project/
├── models/
│   ├── raw_events.sql
│   ├── user_sessions.sql
│   └── user_stats.sql
└── (rest of your project)

Features in Action

Diagnostics:

-- This will show an error
SELECT * FROM {{ ref('nonexistent_model') }}

Go to Definition:

-- Ctrl+Click on 'raw_events' to jump to raw_events.sql
SELECT * FROM {{ ref('raw_events') }}

Syntax Highlighting:

-- Template expressions are highlighted
{{ config(materialized='table') }}

SELECT user_id, COUNT(*)
FROM {{ ref('events') }}
GROUP BY user_id

Configuration

Access settings via: Preferences → Settings → Extensions → sqt

• sqt.serverPath: Path to pre-built smelt-lsp binary (optional)

  • If not set, uses cargo run -p smelt-lsp (slower startup)
  • For better performance, build once and set path:

    cargo build --release -p smelt-lsp
    # Then set path to: target/release/smelt-lsp
    

• sqt.trace.server: Enable server communication tracing for debugging

  • Options: off, messages, verbose
  • Use verbose to debug LSP issues

Troubleshooting

Language server not starting

Check Output:

1. View → Output
2. Select "sqt Language Server" from dropdown
3. Look for error messages

Common Issues:

• Cargo not found: Ensure Rust toolchain is installed and in PATH
• No workspace folder: VSCode needs an open folder (not just files)
• No models/ directory: Create a models/ directory with .sql files

Diagnostics not showing

1. Check that file is in models/ directory
2. Check file has .sql extension
3. Try saving the file (triggers re-analysis)
4. Check Output panel for errors

Go-to-definition not working

1. Ensure the referenced model exists
2. Model file should be in models/ directory
3. Model name should match filename (e.g., {{ ref('users') }} → models/users.sql)

Development

To work on the extension:

cd editors/vscode

# Install dependencies
npm install

# Compile TypeScript
npm run compile

# Watch mode (auto-recompile on changes)
npm run watch

# Package for distribution
npm run package

Known Limitations

• Parser is currently naive (string matching for {{ ref() }})
• Diagnostics don't show exact line/column yet
• No auto-completions yet (coming soon)
• Full file sync (will add incremental sync)

Roadmap

• [ ] Auto-completions for model names in ref()
• [ ] Hover to show model schema and dependencies
• [ ] Code actions for optimization suggestions
• [ ] Incremental file sync
• [ ] Better error messages with exact positions
• [ ] Syntax highlighting for nested SQL in templates

License

MIT License - See LICENSE file for details