S7-LSP

Language Server Protocol server implementation for Siemens S7 PLC languages.

Provides code intelligence for SCL/Structured Text and Siemens resource files in compatible editors and LSP clients.

Phases 1 through 4 from the product roadmap are complete: syntax support, semantic analysis, completion, and .s7res resource-file support are implemented. AWL/STL remains deferred.

Still in development. Currently in Python for easy prototyping. When I finish, I'll most likely move to lighter, faster implementation, maybe Rust.

Supported Languages

Extension	Language	Status
.scl, .st	SCL / Structured Text	Phases 1-3 ✅
.s7dcl, .udt, .db	SCL Declarations	Phases 1-3 ✅
.s7res	Resource Files	Phase 4 ✅
.awl	AWL / Statement List	Deferred

Features

Implemented

• Syntax diagnostics — parser errors with line/column positions
• Semantic diagnostics — undeclared variables, unknown type/block references, duplicate declarations, invalid assignments, and related semantic checks
• Document symbols — hierarchical outline of blocks, VAR sections, and declarations
• Workspace symbols — search across all open files, including resource entries
• Go-to-definition — jump to variable, block, DB field, and type declarations across open documents
• Find references — locate symbol usages, with optional inclusion of declarations
• Hover — variable, block, and built-in type information at the cursor
• Auto-completion — keywords, variables, built-in types, UDTs, named parameters, block names, and member access
• Resource file support — .s7res parsing, diagnostics, and symbol indexing for MLC_ entries

Roadmap

• Grammar hardening and optimization — broader real-world corpus testing, parser performance work, and incremental document sync
• AWL/STL support — deferred and not part of the active roadmap

Installation

pip install s7-lsp

Or install from source:

git clone https://github.com/Czarnak/s7-lsp.git
cd s7-lsp
pip install -e .

Verify installation:

s7-lsp --version

Development

# Clone and install in development mode
git clone https://github.com/Czarnak/s7-lsp.git
cd s7-lsp
pip install -e .

# Lint
pip install ruff
ruff check src/
ruff format src/

# Type check
pip install mypy
mypy src/s7_lsp/ --ignore-missing-imports

# Test
pip install pytest
pytest -q

Architecture

s7-lsp/
├── src/s7_lsp/
│   ├── __main__.py          # CLI entry point (stdio)
│   ├── server.py            # pygls LSP server setup
│   ├── workspace.py         # Document state management
│   ├── ast_nodes.py         # AST dataclasses
│   ├── parsers/
│   │   ├── scl_grammar.lark # SCL grammar (lark EBNF)
│   │   ├── scl_parser.py    # SCL parser + fallback scanner
│   │   ├── resource_*.py    # Resource file grammar and parser
│   │   └── awl_*.py         # AWL/STL parser stubs (deferred)
│   ├── semantic/            # Symbol table, scopes, semantic checks, type info
│   └── features/            # LSP feature handlers
│       ├── diagnostics.py   # Error/warning reporting
│       ├── symbols.py       # Document/workspace symbols
│       ├── completion.py    # Context-aware completion
│       ├── hover.py         # Hover information
│       ├── definition.py    # Go-to-definition
│       └── references.py    # Find references

License

MIT