Unwrapping static switch cases with `--minify-syntax`

[Ragnar-Oock]

When a switch statement can be statically analyzed to have only one branch (because of a defined value, a resolved typeof, or any other static switch value), it should be unwrapped instead of remaining as a useless wrapper.

for example here is a polymorphic function that resolves an object differently based on the type of the first parameter : in esbuild playground

source for the minimal reproduction

function resolveSource(target) {
    switch ('string' /* infered by TS from "typeof target" */) {
        case 'string':
        case 'symbol': {
            console.log('service id syntax');
            return {};
        }
        case 'function': {
            console.log('target getter syntax');
            return {};
        }
        case 'object': {
            console.log('direct target syntax');
            return {};
        }
        default: {
            if (import.meta.env.DEV) {
                warn(new TypeError(`incorrect target provided to onEvent, typeof target === ${typeof target}, expected string, symbol, function or object`));
            }
            return {};
        }
    }
}

resolveSource("service");

When built with --minify-syntax, only the "string" branch remains :

function resolveSource(e) {
  switch ("string") {
    case "string":
    case "symbol":
      return console.log("service id syntax"), {};
  }
}

But it could be minified further, as only a single branch remains, and it has to be executed if the switch is evaluated, the body of the case should then be unwrapped to something like :

function resolveSource(e) {
  return console.log("service id syntax"), {};
}

[hyrious]

Interestingly Rollup doesn't delete much code for this case.

[Ragnar-Oock]

terser however returns only console.log("service id syntax"); from the whole snippet (can't find a way to share from the REPL ). I don't think expecting esbuild to be that thorough would be any help as it's not esbuild's main concern tho.