Can't test existence of export when using externals

[Janpot]

// ./index.js
import * as external from 'external';
console.log(`External has export "nonExisting": ${!!external.nonExisting}`);

Build as

esbuild index.js --bundle --outfile=out.js --external:external --format=esm

Results into

// index.js
import {
  nonExisting
} from "external";
console.log(`External has export "nonExisting": ${!!nonExisting}`);

Which has different runtime behavior than the original. It will fail importing instead of logging "External has export "nonExisting": false"

Uncaught SyntaxError: The requested module '...external' does not provide an export named 'nonExisting'