ESLint rule to require one variable declaration statement per line? - eslint

Question

Is there an eslint (or typescript-eslint) rule to require each var/let/const statement appear on its own line? I've tried one-var, one-var-declaration-per-line, and max-statements-per-line. From my experiments, max-statements-per-line is too aggressive, targeting some single-line patterns we commonly use. The other two rules don't correctly catch multiple var statements on one line. Is there another rule or configuration I'm overlooking?
Specific example:
let foo: string; let bar: string;
let blah = function blah() { console.log('woot'); };
.eslintrc:
{
"rules": {
// "max-statements-per-line": "error",
"one-var": [ "error", "never" ],
"one-var-declaration-per-line": [ "error", "always" ]
}
}
No errors reported given this config. Uncommenting the max-statements-per-line rule flags both lines. I'd like a ruleset that flags the first line, but allows the second.

Answer 1

The rules you list only apply to single statements (i.e. things where it's invalid to put a ; in the middle). What you have there are multiple statements on a single line. It would be similar if you did:
console.log('foo'); console.log('bar');
You can prohibit any lines with 2 statements using:
"max-statements-per-line": ["error", { "max": 1 }],
Tip: There are a ton of these types of issues that are all covered by the prettier formatter, and you can integrate it into eslint so that anything it sees as improperly formatted is also a linting error. This issue, all types of spacing/indention issues, wrappable lines, and more all come "for free".
extending plugin:prettier/recommended disables a bunch of other rules that would normally conflict, so you can leave out a lot of things from the eslint config like quotes, semi, arrow-parens, etc. because they'll be disabled anyway.
{
"parser": "#typescript-eslint/parser",
"plugins": [
"#typescript-eslint/eslint-plugin",
"#typescript-eslint"
],
"extends": [
"eslint:recommended",
"plugin:#typescript-eslint/recommended",
// prettier configs must come last to disable conflicting rules!
"prettier",
"plugin:prettier/recommended"
]
"rules": {
// ...
}
}