Leaking global 'exports' variable

[jessewmc]

If I declare const exports = ... in an entry point or any included modules I get the following error:

index2.js:1:6: error: "exports" has already been declared
const exports = "Hi";
      ~~~~~~~
1 error

Is this intentional for one of the non-es module specs? It looks like it might have something to do with the runtime.

(As an aside, it would be nice to have the option to build without the runtime if it's not needed.)

Heres a trivial example of the runtime that gets generated when I remove the collision by hand. It seems like exports = module.exports; could be related.

((modules, entryPoint) => {
  let global = function() {
    return this;
  }();
  let cache = {};
  let require = (target, arg) => {
    if (typeof target === "number") {
      let module = cache[target], exports;
      if (!module) {
        module = cache[target] = {
          exports: {}
        };
        modules[target].call(global, require, module.exports, module);
      }
      exports = module.exports;
      if (arg && (!exports || !exports.__esModule)) {
        if (!exports || typeof exports !== "object") {
          exports = {};
        }
        if (!("default" in exports)) {
          Object.defineProperty(exports, "default", {
            get: () => module.exports,
            enumerable: true
          });
        }
      }
      return exports;
    }
    arg.__esModule = () => true;
    for (let name in arg) {
      Object.defineProperty(target, name, {
        get: arg[name],
        enumerable: true
      });
    }
  };
  return require(entryPoint);
})({
  0() {
    // index2.js
    const exports1 = "Hi";
    console.log(exports1);
  }
}, 0);

[jessewmc]

I should clarify that unlike the other issue I filed, I have actually confirmed this with 0.4.3!

Also, to reproduce:

esbuild --bundle --outfile=index-built.js index.js

With index.js as:

const exports = "Hi";
console.log(exports);

Only happens when passing --bundle.

[evanw]

This happens because esbuild supports CommonJS, which declares an implicit variable called exports in the same scope. You'll get the exact same behavior with node, which supports CommonJS:

$ cat example.js
const exports = "Hi";
console.log(exports);

$ node example.js
/Users/evan/dev/esbuild/example.js:1
const exports = "Hi";
      ^

SyntaxError: Identifier 'exports' has already been declared
    at wrapSafe (internal/modules/cjs/loader.js:1070:16)
    at Module._compile (internal/modules/cjs/loader.js:1120:27)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1176:10)
    at Module.load (internal/modules/cjs/loader.js:1000:32)
    at Function.Module._load (internal/modules/cjs/loader.js:899:14)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:74:12)
    at internal/main/run_main_module.js:18:47

Can you share more information about what you are trying to do? What does your full file look like?

[jessewmc]

I'm building a browser bundle, everything is is an es6 module--no commonjs or amd. I'm targeting esnext. There are a few hundred modules, it just so happened that there were a couple declaring const exports at their top level scopes (for no good reason).

It was no problem for me to change once I realized what was going on, just surprising to see a collision with a non-reserved word (at least in ecmascript) that is private to a module.

I normally use rollup (& terser), but esbuild gets me from ~1 minute build time to less than a second, which is amazing.