S7 Lint for VS Code

S7 Lint for VS Code is an extension for static analysis and editor support for Siemens TIA Portal source and export formats.

This is an independent open-source project. It is not an official Siemens product and is not affiliated with, endorsed by, sponsored by, or maintained by Siemens AG. Siemens, SIMATIC, TIA Portal, and other product names are trademarks of their respective owners.

The extension is currently version 0.1.0 and under active development. It is intended to catch common structural, type, symbol, and instruction-call errors before code is imported or compiled in TIA Portal. It is not a replacement for the target CPU and TIA Portal compiler.

Supported files

• .scl: authored SCL files containing one or more block or type declarations.
• .s7dcl: LAD/FBD declaration exports, program blocks, and TYPE declarations.
• .udt: text-format PLC data type declarations.
• PLC data types/**/*.xml: XML PLC data type exports used by the workspace type cache.
• .s7res: multilingual resources used by definition, rename, and inline-hint support.

Current capabilities

Diagnostics

• Validates LAD/FBD and SCL instruction names, pins or parameters, call shape, language availability, templates, results, and selected memory-area rules against the registries under resources/.
• Checks LAD/FBD rung connectivity back to wire#powerrail.
• Checks SCL syntax structure, undeclared identifiers, illegal member access, condition types, expression types, conversions, loop constraints, and instruction-result usage.
• Checks literals and resolvable operands against declared or expected types.
• Builds a workspace type cache for UDT dependencies, duplicate declarations, circular references, array bounds, and nesting limits.
• Applies declaration-section, reference, pointer, array, and selected cross-parameter rules where the required context is available.

The parser and checks are deliberately conservative: when a type, target, or expression cannot be resolved confidently, the extension avoids guessing.

Editor support

• Context-aware completion for declarations, types, instructions, symbols, and top-level block templates.
• Hover, definition, rename, and semantic-token providers.
• Definition and rename support for .s7res multilingual resources.
• Quick fixes for explicit expression conversions and instruction instances.
• Inline multilingual-text hints with configurable locale fallback.

Knowledge bases

The YAML under resources/ is hand-maintained source data and is loaded directly at runtime:

• instruction-registry/: LAD/FBD and SCL instruction signatures.
• type-registry/: base types, system types, expression domains, composition rules, and declaration constraints.
• diagnostic-registry/: diagnostic codes, severities, and message templates.
• system-registry/: shared memory-area and instruction-result schemas.

There is no generated mirror or synchronization step for these registries.

Repository layout

./
  src/                         extension, parsers, analysis, providers, linters
  resources/                   runtime YAML registries
  docs/fbd-knowhow/            LAD/FBD syntax and fixture-derived notes
  docs/source-document-format/ independent source-format interoperability notes
  scripts/                     test runners and stable fixtures
  syntaxes/                    VS Code language grammar and configuration
  themes/                      bundled VS Code theme

Build and test

Run commands from the repository root:

npm install
npm test

npm test compiles the extension and runs all regression suites:

The diagnostic fixtures and their assertion contracts are documented in scripts/fixtures/scl-diagnostics/.

Press F5 in VS Code with this directory open to launch an Extension Development Host. The launch configuration compiles and bundles the extension first.

Package a VSIX

npm run bundle
npx @vscode/vsce package

Commands and settings

The extension contributes these commands:

• S7 Lint: Rebuild Type Cache
• S7 Lint: Re-lint All Open Files
• S7 Lint: Show Loaded Rule Stats

tiaLint.mlcLocale selects the preferred locale for multilingual resource resolution. Resolution falls back to en-US and then to an available locale.

Known limitations

• Target CPU family and firmware are not project configuration inputs yet. platform-availability.NOTLOADED.yaml is reference data and is intentionally not loaded.
• Type checks skip unresolved symbols and expression shapes for which a safe, single result type cannot be inferred.
• XML UDT parsing has no per-member source positions, so XML cache diagnostics are reported on line 1.
• The workspace type and block caches rebuild in full after relevant file changes rather than incrementally.
• shape-only registry entries provide useful call-shape validation but do not justify the same hard-error confidence as confirmed-compiled entries.

Source-format scope and attribution are documented separately in docs/source-document-format/.

License

Licensed under the Apache License 2.0.