Unexpected token 'delete' about esmock

[mcbalomirean]

@iambumblehead Sure, here's a .zip with a small project. Error should repro when you run test.

esmock-unexpected-token-delete.zip

[mcbalomirean]

Thank you for looking at this, After looking at your replies, I managed to work around the issue by doing something like the following:

import esmock from "esmock";

await esmock("../src/to_test.js", {
  "../src/some_module.js": {
    default: {
      delete: () => {
        console.log("Oh no, I've been mocked.");
      },
    },
  },
});

The original code (not the test package I uploaded, but the actual code I'm working on) exported an object which had the delete method in it, and when mocked (by giving ESMock an object with a delete method as the mock) it would be interpreted as if it were exported separately, i.e. export const delete as you mentioned. What I was expecting was that the object I'm passing as the mock be interpreted as the default export, which was a misunderstanding I had.

When I made the test package I got the export scenario wrong, which didn't help me in illustrating the problem. 😅 Instead of exporting contents it should have been something like:

export default {
  delete: () => {
    console.log("deleted");
  },
};

I hope this helps anyone encountering this problem in the future.

[Swivelgames]

Have you tried wrapping the property name? I'm not entirely sure if this is specifically an issue with esmock, and more so JavaScript not liking the fact that you're trying to use a keyword when its expecting to see an object member identifier.

Try this instead:

await esmock('./path/to/module.js', {
    './path/to/dependency.js': { 'delete': () => {} }
})

Please close the issue if this resolved the problem! 🙂

[mcbalomirean]

Unfortunately, that didn't work. I've tried wrapping the function name in a variety of ways and it didn't solve the problem.
I haven't encountered this problem with other mocking frameworks, or with the native ESM loader, so I don't believe it's a problem with JavaScript. If it were a problem with JavaScript, Express.js would be the first to raise some issues because they have delete functions, as do many other frameworks that could be mocked.

[iambumblehead]

@mcbalomirean if you could possibly make a small reproduction demonstration, that would be really great an helpful

[iambumblehead]

could try to make a reproduction myself later but might need to do so on Friday or Saturday (busy today)

[iambumblehead]

@mcbalomirean thanks that's a terrific reproduction

[iambumblehead]

@mcbalomirean looking at the test package you uploaded... the mock definition there is not correct. The original file "some_module.js" exports the name "contents" and does not export "delete". Try mocking "contents" using changes in this diff

import esmock from "esmock";

await esmock("../src/to_test.js", {
  "../src/some_module.js": {
+  contents: {
    delete: () => {
      console.log("Oh no, I've been mocked.");
    },
+  }
  },
});

[iambumblehead]

exporting "delete" is disallowed by node. closing this issue but if there is a misunderstanding or some reason to reopen feel free to reopen

$ echo "export const delete = 1" >> test.mjs && node test.mjs
file:///home/bumble/test.mjs:1
export const delete = 1
             ^^^^^^

SyntaxError: Unexpected token 'delete'
    at DefaultModuleLoader.moduleStrategy (node:internal/modules/esm/translators:116:18)
    at DefaultModuleLoader.moduleProvider (node:internal/modules/esm/loader:206:14)
    at async link (node:internal/modules/esm/module_job:67:21)

Node.js v20.2.0