A customizable, stand-alone linter for Ethereum's Solidity
Latest commit 6189db2 Jan 27, 2017 @duaraghav8 committed on GitHub Update LICENSE



Solium is a linter for Solidity which uses Abstract Syntax Trees and allows the user to enable/disable existing rules and add their own ones!

It internally uses solparse to parse your solidity code into a Spider Monkey compliant AST

Solium aims to comply with the official Solidity Style Guide. Follow our blog in order to stay up to date with the latest news.


npm install -g solium


In the root directory of your DApp, run the following:

solium --init

This creates .soliumrc.json and .soliumignore inside your root directory, which have the configuration for the enabled and custom rules and files and folders to ignore while running the linter respectively.

You can disable a particular rule by setting its value to false in .soliumrc.json

In order to lint a specific file, use:

solium --file foobar.sol

To run the linter over your entire project, use the following command in your root directory:

solium --dir .

This lints all the files inside your project with .sol extension.

Additional Options

  1. Use solium --watch to enable Hot loading (Hot swapping).

  2. When new rules are added in subsequent versions and you update Solium, you need not re-initialize with --init. Simply run solium --sync in your root directory and it automatically adds the newly added rules to your .soliumrc.json. The sync option doesn't change anything else in your configuration files.

  3. Use solium --dir <DIRECTORY_NAME> to run the linter over a particular directory

  4. Use solium --reporter=gcc or solium --reporter=pretty to configure the output

Plugging in your custom rules

-> Open up the .soliumrc.json configuration file and set the value of custom-rules-filename to the path of the file that defines your rules. You can either provide an absolute path or a path relative to the directory in which .soliumrc.json resides. For example: "custom-rules-filename": "./my-rules.js"

The format for writing your custom rule file (for example, my-rules.js) is:

module.exports = {
  'my-rule-name-1': function (context) {
    //Solium internally uses EventEmitter and emits an event every time it enters or leaves a node during the Depth First Traversal of the AST
    context.on ('IfStatement', function (emittedObject) {

      //exit property is set to true if we are leaving the node
      if (emittedObject.exit) {

      //View the node representing an If Statement 
      console.log (emittedObject.node);

      //report an error
      context.report ({
        node: emittedObject.node,
        message: 'I JUST ENTERED AN IF STATEMENT!!',
        location: { //optional
          line: 1,  //optional
          column: 2 //optional


  'my-rule-name-2': function (context) {
    context.on ('ContractStatement', function (emittedObject) {
      //similarly define this rule to do something with Contract Declarations

NOTE: The best way to know which event you're looking for is to simply install solparse or solidity-parser, then parse your code into the AST and see the value of the type field of the node that you wish to target.

See the existing rules to get an idea of how the rules are making use of the context object being provided to them.

-> Then, inside the rules object in the same file, set your rule names to true. For instance:

"rules": {
  "my-rule-name-1": true,
  "my-rule-name-2": true

NOTE: If you write a rule whose name clashes with the name of a pre-defined rule, your custom rule overrides the pre-defined one.

Integrate Solium in your app

To access Solium's API, first install it:

npm install --save solium


let Solium = require ('solium'),
  sourceCode = 'contract fOO_bar { function HELLO_WORLD () {} }';
  //sourceCode can alternatively be a Buffer object

let errorObjects = Solium.lint (sourceCode, {
  'custom-rules-filename': null,  //see above if you wish to add custom rules
  rules: {
    camelcase: true,
    mixedcase: true

errorObjects.forEach ( (err) => {
  console.log (err);

For a list of all available rules, see solium.json.


Please see the Developer Guide to understand how to contribute rules to this repository.


Clone the repository, traverse to the root directory of the project, then install dependencies:

npm install

Running Tests

npm test

Contributors and Testers

Elena Dimitrova

Federico Bond

Christopher Gewecke

Ulrich Petri