Compiler doesn't remove unreachable branches

This can be a limitation of the compiler. Input:

const flags = {
    "enabled": false
};

if (!flags["enabled"]) {
    console.log("not enabled");
} else {
    console.log("enabled");
}

if (flags["otherOption"]) {
    console.log("other option");
}

Command:

java -jar node_modules/google-closure-compiler/compiler.jar  --entry_point input.js \
  --compilation_level ADVANCED_OPTIMIZATIONS \
  --isolation_mode IIFE input.js 

Output:

(function(){var a={enabled:!1};a.enabled?console.log("enabled"):console.log("not enabled");a.otherOption&&console.log("other option");}).call(this);

I would expect the output to only contain one console.log as other branches are unreachable. Is this not possible, e.g. is it unable to determine these conditions in compilation time?

[kosik86]

@ChadKillingsworth this makes sense. I think my example was oversimplified. I use javascript modules and I was hoping that closure compiler can help removing unused functions in these modules if they all share the same config object.

The structure is going to be very similar, but the function is imported from a module.

[ChadKillingsworth]

Not sure why the function is causing problems, but you are going to get much better elimination if you aren’t depending on CollapseProperties. Variables work much more dependably than object properties for this.