Rule proposal: no-code-in-comments

While developing, I frequently try different solutions, and end up with commented-out code, which I occasionally even commit. I’d like for ESLint to warn me about this.

How to detect code

A line of code ends with one of the following characters: {}; .

• Advantages: Simple.
• Disadvantages: Would miss something like //console.log('test'), and while testing code ignoring the semicolon is probably common.

An alternative would be to somehow detect valid JS, but that seems unnecessarily complex.

Reporting

Adjacent comments should generate only a single error. You can view the following as a single comment block.

// console.log(1);
// console.log(2);
// console.log(3);

Options

Inline documentation can sometimes contain code, so we need a way to allow some comments, perhaps in comments starting with /**.

Suggested default:

[2, {isCodeRegExp: /[\{\};](\n|$)/, allowRegExp: /^\*/}]

(The options will be transformed into regexps when strings are given.)

[tmsdnl]

Came across a custom rule by @bahmutov: https://github.com/bahmutov/eslint-rules/blob/master/no-commented-out-code.js

Any thoughs?

[ilyavolodin]

I saw that plugin a while back, and it basically runs every comment through espree. If it gets valid AST - it’s commented out code. Problem is, you might have commented out just a few statements, for example, just a case block inside a switch which will not parse properly, but it is still a commented out code.