Overview

This is a proposal - totally fine to reject and close if these aren't worth maintaining.

The compiled runtime.mjs has 5 issues that trip rules from @eslint/js recommended config (no-fallthrough, no-useless-assignment, no-case-declarations). All three have been in ESLint's recommended set since v9+ (the first two since v0.x/v1.x, no-useless-assignment since v9). These are in the TypeScript source and compile through to the rollup output unchanged.

1. no-fallthrough in js-value.ts

The Boolean case in decode() has a nested switch that doesn't cover all values, then falls through to the Number case. This is intentional (an invalid boolean payload gets treated as a number), but there's no annotation marking it so.

case Kind.Boolean:
    switch (payload1) {
        case 0: return false;
        case 1: return true;
    }
// falls through
case Kind.Number:

2. no-useless-assignment in index.ts (2 instances)

swjs_call_function and swjs_call_function_with_this_no_catch initialize let result = undefined then immediately reassign. In swjs_call_function, the init is never read because the catch returns early. In the no-catch variant, it's a straight reassign on the next statement.

// before
let result = undefined;
result = func.apply(obj, args);

// after
const result = func.apply(obj, args);

3. no-case-declarations in index.ts (2 instances)

The two listenMessage callbacks have const declarations in unbraced default: cases. Wrapping with {} scopes the declaration to the case block.

// before
default:
    const unknownMessage: never = message;

// after
default: {
    const unknownMessage: never = message;
}