Circom Language Support

Syntax highlighting, code snippets, and language configuration for the Circom 2.x zero-knowledge circuit language.

The first Circom extension available on Open VSX Registry - works with VSCodium, Eclipse Theia, and other open editors.

Features

Syntax Highlighting

Full TextMate grammar for Circom 2.x including:

• Keywords: pragma, include, template, function, signal, var, component, bus
• Modifiers: input, output, public, parallel, custom
• Control flow: if, else, for, while, do, return
• Constraint operators: <==, ==>, <--, -->, === (styled distinctly from standard operators)
• Signal tags: {binary}, {maxbit} annotations
• Component main: Special highlighting for component main {public [...]} = ...
• Numeric literals: Decimal and hexadecimal (0xFF)
• Comments: Line (//) and block (/* */)
• Template/function calls: Capitalized identifiers recognized as template instantiations

Code Snippets

28 snippets to accelerate Circom development:

Prefix	Description
pragma	Pragma version declaration
include	Include external circom file
circomfile	Full circom file boilerplate
template	Template declaration
templatemain	Template with component main
templateparallel	Parallel template declaration
function	Function declaration
signalinput	Input signal declaration
signaloutput	Output signal declaration
signal	Intermediate signal declaration
signalinputtag	Input signal with tag annotation
component	Component instantiation
componentmain	Main component declaration
componentmainpublic	Main component with public signals
sca	Signal constrain-assign <==
scr	Signal constrain-assign (right) ==>
sal	Signal assign (no constraint) <--
eqc	Equality constraint ===
for	For loop
while	While loop
if	If statement
ifelse	If-else statement
log	Log for debugging
assert	Assert statement
vararray	Variable array declaration
var2d	Variable 2D array declaration
anon	Anonymous component (Circom 2.1+)
tuple	Tuple destructuring assignment
iszero	Inline IsZero gadget pattern

Go-to-Definition

• Ctrl+Click on include paths to open the imported file
• Ctrl+Click on template/function names (e.g., Poseidon) to jump to the definition, even across included files
• Resolves paths relative to the file, then node_modules/, then user-configured circom.includePaths
• Clickable links on include paths for quick navigation

Language Configuration

• Toggle line comments with Cmd+/ / Ctrl+/
• Toggle block comments with Shift+Alt+A
• Auto-closing pairs for {}, [], (), "", /* */
• Bracket matching and highlighting
• Smart indentation (C-style)
• Code folding support

Installation

From Open VSX (VSCodium / Theia)

Search for "Circom Language Support" in the extensions panel, or:

codium --install-extension darkartistry.circom-lang

From VS Code Marketplace

Search for "Circom Language Support" in the extensions panel, or:

code --install-extension darkartistry.circom-lang

From VSIX

Download the .vsix from Releases, then:

codium --install-extension circom-lang-0.2.0.vsix
# or
code --install-extension circom-lang-0.2.0.vsix

Supported Circom Versions

• Circom 2.0.x
• Circom 2.1.x (anonymous components, tuples, signal tags, bus)

Roadmap

• v0.3: Diagnostics - red/yellow squiggly lines from circom --inspect
• v1.0: LSP integration - hover docs, auto-completion

Contributing

Issues and pull requests welcome at github.com/darkartistry/vscode-circom.

License

MIT