Fix: one-var shouldn't split declaration if it isn't in a statement list

[mdjermanovic]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request? (put an "X" next to an item)

[ ] Documentation update
[x] Bug fix (template)
[ ] New rule (template)
[ ] Changes an existing rule (template)
[ ] Add autofixing to a rule
[ ] Add a CLI option
[ ] Add something to the core
[ ] Other, please explain:

Tell us about your environment

• ESLint Version: v7.16.0
• Node Version: v12.18.4
• npm Version: v6.14.6

What parser (default, @babel/eslint-parser, @typescript-eslint/parser, etc.) are you using?

default

Please show your full configuration:

Configuration

module.exports = {
  parserOptions: {
    ecmaVersion: 2015
  }
};

What did you do? Please include the actual source code causing the issue.

Online Demo

/* eslint one-var: ["error", "never"] */

do 
    var x = f(), y = b();
while (x < y);

What did you expect to happen?

Given that this rule already reports errors that require non-trivial manual fixes, I'd expect an error without the autofix. This code can be fixed by adding a block (or in some other way), but that seems out of scope for this rule.

What actually happened? Please include the actual, raw output from ESLint.

Error with autofix that produces a syntax error:

/* eslint one-var: ["error", "never"] */

do 
    var x = f(); var y = b();
while (x < y);

  4:18  error  Parsing error: Unexpected token var

What changes did you make? (Give an overview)

Fixed splitDeclarations() to produce a fix only if the given VariableDeclaration is in a statement list, i.e. if it is a child of Program, BlockStatement, or SwitchCase node.

Autofix will not be provided if the reported declaration is a direct child of if, while, do-while, for, for-in, for-of or with, or if it is labeled.

Is there anything you'd like reviewers to focus on?

There's also a false negative in SwitchCase nodes when the option is "consecutive" (I'll fix that in another PR), and inconsistent behavior with export-ed declarations (I'll open an issue for that).

[yeonjuan]

LGTM! Thanks 👍

[aladdin-add]

LGTM! 💯