ControlForge Structured Text

Professional Structured Text (IEC 61131-3) development environment for PLC programming in Visual Studio Code.

Key Features

• Code Formatting: Format Document, Format Selection, configurable keyword casing, operator spacing, VAR alignment
• Real-time Diagnostics: Errors and warnings as you type — missing semicolons, type mismatches, undefined/unused variables, unmatched blocks
• Code Actions & Quick Fixes: One-click fixes for missing END blocks, semicolons, duplicate/unused declarations, unclosed strings
• Rename Symbol (F2): Rename variables, functions, FBs, programs across all workspace files with IEC 61131-3 validation
• Go to Definition & Find References: Cross-file symbol navigation
• Signature Help: Parameter hints for functions/FB calls with active argument highlight
• Function Block IntelliSense: Auto-complete for FB members (myTimer.Q, upCounter.CV)
• Rich Syntax Highlighting: Complete IEC 61131-3 language support
• Smart Code Completion: Context-aware suggestions for keywords, types, and variables
• Workspace Indexing: Automatic cross-file symbol discovery and resolution
• Code Snippets: Pre-built templates for common PLC patterns

Getting Started

Installation

1. Open Visual Studio Code
2. Go to Extensions (Ctrl+Shift+X)
3. Search for "ControlForge Structured Text"
4. Click Install

Commands

Access via the Command Palette (Ctrl+Shift+P):

• ControlForge Structured Text: Validate Syntax - Check current file for syntax errors
• ControlForge Structured Text: Check LSP Status - Verify Language Server is running
• ControlForge Structured Text: Show Index Statistics - Display indexed workspace symbols

Quick Start

1. Create a new file with .st or .iecst extension
2. Start typing - syntax highlighting activates automatically
3. Use Ctrl+Space for IntelliSense completion
4. Type function block instances followed by . for member completion
5. Type ( or , in function/FB calls for parameter hints (Ctrl+Shift+Space manual trigger)

Function Block Completion Example

PROGRAM MyProgram
VAR
    startTimer : TON;          // Timer On-Delay
    partCounter : CTU;         // Counter Up
    emergencyStop : R_TRIG;    // Rising Edge Trigger
END_VAR

// IntelliSense in action:
startTimer.     // Shows: Q (BOOL), ET (TIME)
partCounter.    // Shows: Q (BOOL), CV (INT)
emergencyStop.  // Shows: Q (BOOL)
END_PROGRAM

Language Features

Smart IntelliSense

• Function Block Members: Auto-complete for all standard IEC 61131-3 function blocks
  • Timers: TON, TOF, TP → Q, ET
  • Counters: CTU, CTD, CTUD → Q, CV, QU, QD
  • Edge Detectors: R_TRIG, F_TRIG → Q
  • Bistables: RS, SR → Q1
• Keyword Completion: All IEC 61131-3 keywords and constructs
• Data Type Suggestions: BOOL, INT, REAL, TIME, STRING, etc.
• Variable Detection: Automatically detects declared variables
• Code Snippets: Templates for common patterns (IF-THEN, FOR loops, etc.)

Signature Help

• Call hints: Shows function/FB signature on ( and ,
• Active parameter: Highlights current argument as you move through call parameters
• Manual trigger: Use Ctrl+Shift+Space to re-open parameter hints
• Coverage: Standard functions (LIMIT, ABS, SQRT, LEN, etc.), standard FBs (TON, CTU, R_TRIG, etc.), and custom workspace functions/FBs

Navigation

• Go to Definition: Jump to symbol declarations across files
• Find References: Locate all usages of a symbol
• Rename Symbol (F2): Cross-file rename with IEC 61131-3 validation — rejects keywords, data types, standard functions
• Member Access Navigation: Navigate from instance.member to FB definitions
• Hover Information: Rich tooltips for standard FBs with parameter tables, behavior, and usage examples

Diagnostics

• Real-time error detection: Errors appear as you type with 300ms debounce
• Unmatched blocks: Missing END_PROGRAM, END_IF, END_VAR, etc.
• Unclosed strings: Single-quoted (STRING) and double-quoted (WSTRING)
• Unmatched parentheses: Per-line detection with string/comment awareness
• Missing semicolons: Detects missing ; on statement lines in POU bodies
• Duplicate declarations: Same-name variables in the same scope (case-insensitive)
• Undefined variables: Identifiers used but not declared, with fuzzy "did you mean?" matching
• Unused variables: Local variables declared but never referenced in body
• Type mismatches: Incompatible assignments (e.g., STRING to INT, BOOL to INT)
• CONSTANT assignment: Assignment to VAR CONSTANT or VAR_GLOBAL CONSTANT variables flagged as error
• Array bounds: Out-of-bounds literal index on ARRAY[L..U] variables flagged as error (single- and multi-dimensional)
• FOR loop bounds: BY 0 flagged as error; reverse range (e.g. 10 TO 1 BY 1) flagged as warning; single-iteration (5 TO 5) flagged as hint; only constant bounds checked
• Problems panel: All diagnostics surface in Ctrl+Shift+M with source "ControlForge ST"
• Case-insensitive: Keyword matching per IEC 61131-3

Code Actions & Quick Fixes

• Missing END blocks: Auto-insert END_IF, END_FOR, END_WHILE, END_CASE, END_PROGRAM, END_FUNCTION, END_FUNCTION_BLOCK, END_VAR, etc.
• Unclosed strings: Append closing quote (single or double) at end of line
• Unmatched parentheses: Insert missing closing ) at end of expression
• Missing semicolons: Insert ; at end of statement
• Duplicate declarations: Remove duplicate variable declaration line
• Unused variables: Remove unused variable declaration line
• Missing variable declarations: Auto-declare undefined variables with inferred types; batch-fix all missing declarations at once
• Light bulb menu: Fixes appear via Ctrl+. or clicking the light bulb icon

Code Formatting

• Format Document: Format entire file via Command Palette (Ctrl+Shift+P > Format Document)
• Format Selection: Format only selected code
• Keyword casing: Configurable UPPER, lower, or preserve
• Operator spacing: Automatic spaces around :=, +, -, *, /, =, <>, <=, >=
• Indentation: Automatic block-level indent for IF/FOR/WHILE/CASE/REPEAT, VAR sections, POU bodies
• VAR alignment: Align colon positions across declarations in VAR blocks
• Trailing whitespace: Automatic removal
• Settings: All formatting options configurable via structured-text.format.*

Syntax Highlighting

• Keywords: IF, THEN, ELSE, FOR, WHILE, CASE, VAR, END_VAR
• Data Types: BOOL, INT, REAL, TIME, STRING, ARRAY, STRUCT
• Operators: AND, OR, NOT, XOR, :=, +, -, *, /
• Comments: // single-line and (* *) multi-line
• Literals: String, numeric (decimal, hex, binary), time literals
• Function Blocks: Standard IEC 61131-3 function blocks

Editor Features

• Auto-closing: Brackets, quotes, and parentheses
• Comment Toggle: Ctrl+/ for quick commenting
• Word Matching: Intelligent word selection and highlighting
• File Association: Automatic recognition of .st and .iecst files

Supported File Extensions

• .st - Standard Structured Text files
• .iecst - IEC 61131-3 Structured Text files

Requirements

• Visual Studio Code 1.100.0 or higher
• Operating System: Windows, macOS, or Linux

What's New in v1.3.0

• Rich FB Hover Tooltips: Standard function blocks show parameter tables, behavior descriptions, and usage examples on hover
• Advanced Diagnostics: Missing semicolons, duplicate declarations, undefined variables, unused variables, type mismatches — all with quick fixes
• Code Formatting: Format Document and Format Selection with keyword casing, operator spacing, indentation, VAR alignment
• Rename Symbol (F2): Rename variables, functions, FBs, programs with identifier validation and comment-awareness
• Code actions & quick fixes: Auto-insert missing END blocks, close unclosed strings, fix unmatched parentheses via light bulb menu
• Real-time diagnostics: Unmatched blocks, unclosed strings, unmatched parentheses shown in Problems panel as you type
• Multi-line declaration parsing: Arrays, structs, and complex initializers now parse correctly
• 465 unit tests: Comprehensive coverage for all LSP providers, diagnostics, code actions, rename, and formatting

What's New in v1.2.5

• Multi-line declaration parsing: Arrays, structs, and complex initializers now parse correctly
• VAR qualifier support: VAR_GLOBAL CONSTANT, VAR RETAIN, etc.
• Complex type support: STRING[n], POINTER TO, REFERENCE TO, multi-dim ARRAY
• Case-insensitive symbol lookup: IEC 61131-3 compliant across all symbol types
• Memory leak fix: Proper index cleanup on file close, debounced re-parsing
• Performance: 300ms debounce on document changes

What's New in v1.2.0

• Go to Definition & Find References: Cross-file symbol navigation
• Language Server Protocol (LSP): Full client-server architecture
• Member Access Navigation: Navigate from instance members to definitions
• Workspace Indexing: Automatic cross-file symbol discovery
• IEC 61131-3 Definition Files: Standard FB definitions for hover and completion

Support & Feedback

• Website: controlforge.dev
• Issues: GitHub Issues
• Discussions: GitHub Discussions
• Rate & Review: VS Code Marketplace