Module dynamic imported from cjs output has unexpected exports.

[chenjun1011]

Minimal repro:

// a.js
exports.createElement = function() {
  console.log('createElement')
}

// index.mjs
import { createElement } from './a';

export async function renderToHTML(requestContext) {
  createElement();
}

Esbuild config:

import * as esbuild from 'esbuild'

await esbuild.build({
  entryPoints: ['index.mjs'],
  bundle: true,
  outfile: 'bundle.js',
  target: 'node12.20.0',
  format: 'cjs'
});

Outputted bundle.js:

// ...

// a.js
var require_a = __commonJS({
  "a.js"(exports) {
    exports.createElement = function() {
      console.log("createElement");
    };
  }
});

// index.mjs
var esbuild_demo_exports = {};
__export(esbuild_demo_exports, {
  renderToHTML: () => renderToHTML
});
module.exports = __toCommonJS(esbuild_demo_exports);
var import_a = __toESM(require_a(), 1);
async function renderToHTML(requestContext) {
  (0, import_a.createElement)();
}

When use 'import()' to dynamic load bundle.js

const mod = await import('./bundle.js');
console.log('mod=>', mod);

The module loaded has an unexpected export createElement.

It seems although the exports passed to the module a are not node.js's native exports, it still changed the native exports. This maybe a bug in dynamic import.(The problem only occurs in the case of dynamic import)

If esbuild can avoid the keyword exports in __commonJS function, or provide some overriding configuration
, may solved this problem.

[evanw]

This is a bug in node. Node is trying to guess at what exports the module has and it's guessing wrong. If I rename exports to not_exports then the bug isn't triggered. Node isn't doing the correct scope analysis to determine whether exports is from the top-level module or a nested module. It just makes up an export called foo if it finds an assignment to exports.foo anywhere in the source code, even if exports is a local variable. I can try to have esbuild avoid naming variables exports when targeting node to work around this bug in node.