Dynamic import not working on eval/print

[jkrems]

• Version: 13.2.0
• Platform: macOS
• Subsystem: modules

$ node --input-type=module -p "import('fs')"
Promise {
  <rejected> TypeError [ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING]: A dynamic import callback was not specified.
      [...] {
    code: 'ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING'
  }
}

$ node -e "import('fs')"
(node:41604) UnhandledPromiseRejectionWarning: TypeError [ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING]: A dynamic import callback was not specified.
    at exports.importModuleDynamicallyCallback (internal/process/esm_loader.js:35:9)

$ node --input-type=module -e "import 'path'; import('fs')"
(node:42773) UnhandledPromiseRejectionWarning: TypeError [ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING]: A dynamic import callback was not specified.

The last one seems the most confusing: The same input string works fine with static import but not with dynamic import from the same file. I assume this is a side-effect of tying the import callback to individual scripts instead of to the context.

[GeoffreyBooth]

I just ran into this. I was testing with this code:

import("data:text/javascript,console.log(Date.now())")
.then(console.log).catch(console.error);

If you save this as test.js and run via node test.js, you get expected output like:

1575009791489
[Module] {  }

But run it with --eval, and you get:

✗ node --eval 'import("data:text/javascript,console.log(Date.now())").then(console.log).catch(console.error);'
TypeError [ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING]: A dynamic import callback was not specified.
    at exports.importModuleDynamicallyCallback (internal/process/esm_loader.js:35:9)
    at [eval]:1:1
    at Script.runInThisContext (vm.js:116:20)
    at Object.runInThisContext (vm.js:306:38)
    at Object.<anonymous> ([eval]-wrapper:9:26)
    at Module._compile (internal/modules/cjs/loader.js:1121:30)
    at evalScript (internal/process/execution.js:80:25)
    at internal/main/eval_string.js:23:3 {
  code: 'ERR_VM_DYNAMIC_IMPORT_CALLBACK_MISSING'
}

My use case is I’m trying to find a way to tell Node to evaluate ESM code, without using any of the experimental APIs in VM. Ultimately I want to essentially eval ESM code, without needing to define various functions that are part of the loader, such as this dynamic import callback. I just want to inherit those functions from the ESM loader, the same way node test.js does.

[leotm]

Slightly related, I was doing some playing around:

Any idea what Jest is doing different here to trigger our error at hand?

• node: 13.5.0
• typescript: 3.8.3
• jest: 25.4.0

[devsnek]

They probably didn't provide a dynamic import handler for their vm usage. You should open an issue with them.