Remove unused exports from dynamic imported module

[alan-agius4]

When using a dynamic import, unused symbols are not being tree-shaken (dropped) from the output bundle.

Input Code Example

// main.ts
const { foo } = await import('./dep.js');
console.log(foo);

// dep.js
export const foo = "foo";
export const bar = "bar";

Observed Output

// dep-CH3SPVYO.js (69 bytes)
var foo = "foo";
var bar = "bar";
export {
  bar,
  foo
};

Actual
The bar variable, which is unused in the code, is not being tree-shaken (dropped) as expected. This increases the bundle size unnecessarily.

Expected Output
Only the foo export should be retained in the final bundle because bar is not used in the importing module. The desired output should look like:

// dep-CH3SPVYO.js (40 bytes)
var foo = "foo";
export {
  foo
};

Context
The issue arises even though esbuild is set up with splitting and bundle optimizations enabled. The expectation is that unused exports like bar would be eliminated.

Reproduction Link
The behavior can be reproduced using the REPL: https://esbuild.github.io/try/#YgAwLjI0LjAALS1idW5kbGUgLS1mb3JtYXQ9ZXNtIC0tc3BsaXR0aW5nIC0tb3V0ZGlyPSIvIiAAZQBlbnRyeS5qcwBjb25zdCB7IGZvbyB9ID0gYXdhaXQgaW1wb3J0KCcuL2RlcC5qcycpOwpjb25zb2xlLmxvZyhmb28pAABkZXAuanMAZXhwb3J0IGNvbnN0IGZvbyA9ICJmb28iOwpleHBvcnQgY29uc3QgYmFyID0gImJhciI7