Hydrust

A Language Server for Hydra configuration files, written in Rust.

Features

Currently Implemented

• ✅ YAML Parsing: Extracts _target_ references and their parameters
• ✅ Hover Support: Shows rich information when hovering over _target_ values:
  • Function signatures with parameter details
  • Class information and docstrings
  • Type annotations
• ✅ Go to Definition: Jump from YAML _target_ to Python source file
• ✅ Diagnostics: Parameter validation including:
  • Unknown parameters (unless **kwargs present)
  • Missing required parameters
  • Positional-only parameters passed by name instead of through _args_
  • Basic _target_ format validation
• ✅ Semantic Tokens: Rich syntax highlighting for Hydra configurations:
  • Module path components (namespace tokens)
  • Class and function names
  • Parameter keys (parameter tokens)
  • Values (string, number, and property tokens)
• ✅ Signature Help: Shows parameter information while typing function arguments

Planned Features

For a list of planned features and enhancements, see the issues page.

Installation

You can install hydrust through PyPI:

uv tool install hydrust   # or: pixi global install hydrust, pip install hydrust
uvx hydrust check conf/   # run once without installing

Usage

hydrust provides the check subcommand for one-time CLI and CI invocations, as well as an LSP for hydra diagnostics over stdin/stdout:

hydrust check conf/   # diagnose configs on the command line
hydrust server        # LSP

hydrust check

# Check a single file
hydrust check config.yaml

# Check several files, or a whole directory tree
hydrust check config.yaml overrides.yaml
hydrust check conf/

# Specify workspace root for local module resolution
hydrust check config.yaml -w /path/to/project

# Specify Python interpreter for site-packages resolution
hydrust check config.yaml -p /path/to/venv/bin/python

# Enable detailed resolution tracing for debugging
hydrust check config.yaml --trace-resolution

# Change verbosity level (error, warn, info, debug, trace)
hydrust check config.yaml -v debug

# Output in different formats (pretty, json, compact, github)
hydrust check config.yaml -f json

Directories are searched recursively for .yaml and .yml files. The walk honours .gitignore and .ignore files within the directory being walked, and skips hidden files and directories such as .github/. Symlinks are followed.

Options

When --workspace is omitted, hydrust resolves Python modules against the current directory.

Continuous integration

--output-format github emits GitHub Actions workflow commands, so diagnostics appear as inline annotations on the pull request. A complete workflow, run with uvx so nothing needs installing beyond uv itself:

name: Hydra configs

on: [push, pull_request]

jobs:
  hydrust:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v6
      - uses: astral-sh/setup-uv@v10.2.0
      - run: uvx hydrust@0.5.0 check --output-format github .

_target_ resolution needs the Python packages your configs point at. If they are not in the checked-out tree, install the project first and point hydrust at that interpreter with --python:

      - run: uv sync
      - run: uvx hydrust@0.5.0 check --output-format github --python .venv/bin/python conf/

Exit Codes

• 0: No errors found
• 1: One or more errors found
• 2: Fatal error (path not found, invalid arguments, etc.)

Finding nothing to check is not an error: whether no YAML files matched at all or none of the ones found are Hydra configs, hydrust check warns on stderr and exits 0.

hydrust server

Client Compatibility

A client can be pointed at any released server binary, and an old server quietly ignores settings it was never taught to read. So the server describes itself in capabilities.experimental.hydrust at initialize (HydrustCapabilities::new in src/backend.rs):

• protocolVersion — the version of this block's shape.
• supportedSettings — keys read from initializationOptions.settings.
• supportedRules — codes accepted in disabledRules.
• features — optional behaviours switched on for this session, after matching what the server can do against what the client asked for.

A client that sees the block uses it instead of any built-in table; servers before v0.4.0 send no block, so clients fall back to a version table keyed on serverInfo.version or --version. The reference client is the VS Code extension (hydra-lsp-vscode), in src/common/compatTable.ts.

License

This project is licensed under the MIT License - see the LICENSE file for details.

Acknowledgments

• Built with tower-lsp framework
• Python analysis design based on ruff and ty

References

• Language Server Protocol Specification
• Hydra Documentation
• Tower-LSP Documentation