linter: no-else-return false positive on wrong branch

[camchenry]

What version of Oxlint are you using?

0.9.10

What command did you run?

bunx oxlint@latest -D all -A no-unused-vars -A sort-keys -A no-null -A no-undefined -A explicit-function-return-type -A no-magic-numbers -A no-ternary -A no-explicit-any -A no-const-enum -A prefer-enum-initializers -A no-optional-chaining --ignore-pattern compliance

What does your .oxlint.json config file look like?

N/A

What happened?

While doing some linter testing on the https://github.com/angular/angular repository, I noticed that the no-else-return lint rule was correctly reporting an issue, but was reporting it for a line that is actually an else-if block.

Specifically, this code:

export const getPropType = (prop: unknown): PropType => {
  if (isSignal(prop)) {
    prop = prop();
  }

  if (prop === undefined) {
    return PropType.Undefined;
  }
  if (prop === null) {
    return PropType.Null;
  }
  if (prop instanceof HTMLElement) {
    return PropType.HTMLNode;
  }
  const type = typeof prop;
  if (type in commonTypes) {
    return commonTypes[type as keyof typeof commonTypes];
  }
  if (type === 'object') {
    if (Array.isArray(prop)) {
      return PropType.Array;
    } else if (prop instanceof Set) {
      return PropType.Set;
    } else if (prop instanceof Map) {
      return PropType.Map;
    } else if (Object.prototype.toString.call(prop) === '[object Date]') {
      return PropType.Date;
    } else if (prop instanceof Node) {
      return PropType.HTMLNode;
    } else {
      return PropType.Object;
    }
  }
  return PropType.Unknown;
};

is reported as:

× eslint(no-else-return): Unnecessary 'else' after 'return'.
    ╭─[devtools/projects/ng-devtools-backend/src/lib/state-serializer/prop-type.ts:48:7]
 47 │     if (Array.isArray(prop)) {
 48 │       return PropType.Array;
    ·       ───────────┬──────────
    ·                  ╰── This consequent block always returns,
 49 │     } else if (prop instanceof Set) {
    ·      ───┬──
    ·         ╰── Making this `else` block unnecessary.
 50 │       return PropType.Set;
    ╰────
  help: Remove the `else` block, moving its contents outside of the `if` statement.

I believe this is incorrect, because the following else is part of an if statement, so it doesn't matter if the prior if always returns. It should actually be reporting this code as the error, since all previous if statements return:

} else {
  return PropType.Object;
}

[camchenry]

Ah actually I didn't read the configuration on this rule closely enough, it looks like it already allows for allowElseIf: true which would fix this. Looks to be working as intended.