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VSCode Setup

The rust-plc toolchain includes a VSCode extension that provides full IDE support for Structured Text.

Features

The language server provides 16 LSP features for a full IDE experience:

  • Diagnostics — Real-time errors and warnings as you type (30+ diagnostic codes)
  • Hover — Ctrl+hover shows type info, function signatures, and variable kinds
  • Go-to-definition — Ctrl+Click jumps to variable or POU declarations
  • Go-to-type-definition — Jumps to the TYPE, STRUCT, or FUNCTION_BLOCK declaration of a variable’s type
  • Completion — Auto-complete with keywords (snippets), variables, functions, struct fields (dot-trigger), FB members, and types
  • Signature help — Parameter hints on ( and , inside function and FB calls
  • Find all references — Shift+F12 finds all usages of a symbol (case-insensitive, whole-word)
  • Rename symbol — F2 renames across all occurrences in the file
  • Document symbols — Ctrl+Shift+O outline view with nested POUs and variables
  • Workspace symbols — Ctrl+T search for any POU or type across all open files
  • Document highlight — Cursor on an identifier highlights all occurrences instantly
  • Folding ranges — Collapse PROGRAM, FUNCTION, VAR, IF, FOR, WHILE, CASE, and comment blocks
  • Document links — File paths in comments (e.g., // see utils.st) become clickable links
  • Semantic tokens — 10 token types for rich, context-aware syntax highlighting
  • Formatting — Shift+Alt+F auto-indents the entire file
  • Code actions — Ctrl+. quick fix: declare undeclared variable as INT

Installation

  1. Open the rust-plc repository in VSCode
  2. Click “Reopen in Container” or run Dev Containers: Reopen in Container
  3. Everything is configured automatically

Option B: Extension Development Host

  1. Build the CLI and extension:

    cargo build -p st-cli
cd editors/vscode && npm install && npm run compile

  2. Press F5 in VSCode (with the rust-plc repo open)

  3. Select “Launch Extension (playground)”

  4. A new VSCode window opens with the extension loaded and the playground/ folder open

Option C: Manual Installation

  1. Build st-cli:

    cargo build -p st-cli --release

  2. Package the extension:

    cd editors/vscode
npm install
npm run compile
npx @vscode/vsce package --no-dependencies

  3. Install the .vsix:

    code --install-extension iec61131-st-0.1.0.vsix

  4. Configure the server path in VSCode settings:

    {
  "structured-text.serverPath": "/path/to/st-cli"
}

Configuration

SettingDefaultDescription
structured-text.serverPathst-cliPath to the st-cli binary

File Associations

The extension automatically activates for files with these extensions:

  • .st — Structured Text
  • .scl — Structured Control Language (Siemens variant)

Troubleshooting

Extension not activating

  • Check that st-cli is built and accessible
  • Open the Output panel → select “Structured Text Language Server”
  • Verify the binary path in settings

No syntax highlighting

  • Reload the window: Ctrl+Shift+P → “Developer: Reload Window”
  • Check that the file is recognized as “Structured Text” (bottom-right status bar)

LSP errors

  • Build st-cli: cargo build -p st-cli
  • Check the Output panel for error messages from the language server

Next Steps

Once the extension is installed and working, see the complete walkthrough:

Editing, Running & Debugging in VSCode — step-by-step guide covering hover, completion, diagnostics, running programs, setting breakpoints, stepping through code, and inspecting variables.