feat: `no-case-declarations` add suggestions

JoshuaKGoldberg commented 3 weeks ago

Prerequisites checklist

[x] I have read the contributing guidelines.

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

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

Fixes https://github.com/eslint/eslint/issues/18349

What changes did you make? (Give an overview)

Adds a suggestion fixer to no-case-declarations to add { } brackets around blocks.

Also adds a couple new tests to make sure switches with multiple violating cases report on the right case (consequent).

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

I'd considered adding logic for friendlier { } bracket placement but then decided against the added complexity.

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fasttime commented 3 weeks ago

When a declared identifier is used in another case block, applying the suggestion can change the logic, for example:

// ecmaVersion: "latest"
switch ("foo") {
    case "bar":
        function baz() { }
        break;
    default:
        baz();
}

compared to:

// ecmaVersion: "latest"
switch ("foo") {
    case "bar":
        { function baz() { }
        break; }
    default:
        baz(); // TypeError!
}

I assume this is acceptable for a suggestion, but maybe we should add a unit test to show that we are aware of the risk and we know what we are doing?

eslint / eslint