KiCad Custom Design Rules — VS Code extension

Syntax highlighting and snippets for KiCad Custom Design Rule files (.kicad_dru) in Visual Studio Code.

KiCad ships a single-line textbox in Board Setup → Custom Rules and a Check Rule Syntax button. That works for one-liners. For real rule sets you want a real editor — multi-cursor, search, and colour that distinguishes condition operators from A.NetClass accessors from layer names from string literals. This extension adds that for .kicad_dru specifically.

Features

• Syntax highlighting scoped to .kicad_dru. Keywords (version, rule, constraint, condition, layer, severity, disallow), constraint types (clearance, hole_clearance, track_width, length, assertion, …), token-expression accessors (A.NetClass, B.intersectsArea, …), operators, layer names, severities, comments, strings, and numbers with units are all coloured distinctly.
• Snippets for the common rule shapes: starter rule block, clearance by netclass, disallow, length matching, via and track sizing, hole-to-hole, assertion. Type the prefix in a paren context, accept, tab through.
• IntelliSense completion. Inside (condition "…") / (constraint assertion "…") strings: a receiver and . (A., B., AB.) gets its properties, an identifier boundary gets receivers and functions. While writing the rule structure: after (constraint you get constraint types, after (layer layer names, after (severity severities, after (constraint disallow the categories. Each item shows its type/units or argument shape and a short doc.
• Hover help. Hover a constraint type, property, function, layer, severity, or disallow category to see what it is, its argument/type, and a one-line description.
• Editor niceties: # line comment toggling, paren matching, folding on each top-level (rule …) block, auto-closing pairs.

Completion and hover are backed by a single data/api.json audited against KiCad 10.

What this extension does not do

• It is a highlighter, not a validator. KiCad's own Check Rule Syntax button remains the source of truth for whether a rule is valid.
• It does not parse .kicad_pcb, .kicad_sch, .kicad_sym, or any other KiCad file. Those have other extensions (DanielMeza.kicad-syntax- highlighter covers most of them; oaslananka.kicadstudio covers KiCad workflows end-to-end). This extension intentionally stays focused on .kicad_dru so that DRU support is first-class instead of incidental.
• It does not provide diagnostics (semantic rule validation) yet. That is tracked as later additions.

Installation

From the VS Code Marketplace:

ext install cimos.kicad-dru

Or search for "KiCad Custom Design Rules" in the Extensions view.

A .vsix is also attached to each GitHub release if you prefer manual installation:

code --install-extension vscode-kicad-dru-<version>.vsix

Use with KiCad's External Tools menu

KiCad ≥ 7 supports launching an external editor on a file via Preferences → Configure Paths → External Tools. Pointing it at VS Code gives you a one-click round trip from the KiCad PCB editor to this extension's editor view. Save the file in VS Code, switch back to KiCad, and re-run Check Rule Syntax.

Contributing

Pull requests are welcome — especially for grammar gaps you hit on a real rule file. Please attach a minimal .kicad_dru snippet that demonstrates the issue.

Issues: https://github.com/Cimos/vscode-kicad-dru/issues

License

MIT.