Support for ESM

[emilioSp]

Hello @mastermatt ,
I'm struggling to use this library with vitest.
I think it's related to the fact that vitest is ESM first.
The error is

TypeError: __vite_ssr_import_1__ is not a function

This is a reproducible repo.

Do you have in plan to release nock as an ESM package?

Thanks!

[mastermatt]

@emilioSp I haven't worked with vitest before, or even vite, but there shouldn't be an issue with mixing Nock and vitest as ESM first.

My gut is that the error it self is mostly a red herring from how vite monkey patches Node's built-in require functionality (similar to what Jest does).
Thanks for providing the repo, I was able to get things going by ensuring esModuleInterop was set to true in your ts-config then fixing the nock import.
import nock from 'nock';

Hopefully that's enough to get you going.

[emilioSp]

Hey @mastermatt thanks for your quick response.

Unfortunately, I cannot change the value of esModuleInterop because the ts-config is shared with other projects.
I have also another cjs library (node-config) but It works without problems. (https://stackblitz.com/edit/node-kcts1t?file=my.test.ts)

I'm wondering why...

By the way thanks for your help on this.

[mastermatt]

In that case you might need to pull from .default manually. Something like:

import * as NockImport from 'nock';

const nock = NockImport.default;

I haven't actually tried this, but when you inspect the value of the star import with esModuleInterop: false you should see that it's a plain object with a default key and not the nock function you want.

[emilioSp]

I see!
It works also with

import { default as nock } from 'nock';

the problem is that I got a ts error because

Module '"nock"' has no exported member 'default'

I don't think there is a solution for that 😔

[emilioSp]

I'll add a bit more context. I'm trying to switch from Jest to Vitest...
at this point, I don't have any ideas on how and why jest + ts-jest simply works with

import * as nock from 'nock'

It is a completely different behavior with respect to the standard esm node runtime.
see here.
If you run node index.mjs you get

Error: nock is not a function

which is aligned with what I excepted after our messages exchange.

The same with ts-node index.ts, you get

index.ts:3:1 - error TS2349: This expression is not callable.

[emilioSp]

@mastermatt my bad. There was a typo in the tsconfig name. Now TypeScript is not complaining anymore.

Anyway thanks for your time in helping me with this.

[esamattis]

We observed also some weird behaviour with vitest. For some reason nock was unable to intercept http request in some situations when using the node.js http and https modules directly. Unfortunately I've not been able to make a repro because it only appears with our fairly complicated project setup. But we found a workaround which might help others:

Instead of using import just use require().

Ex. here's how we kept the typescript type around:

import * as https from "https";
import * as http from "http";

const https = require("https") as typeof import("https");
const http = require("http") as typeof import("http");

We have esModuleInterop set to true in our tsconfig.json if that matters.