Could it be a problem to use a fetch?

[krutoo]

Hi, in readme of this project I see this chapter:
https://github.com/nodejs/undici?tab=readme-ov-file#garbage-collection

This section says that the body must be read.

I have small library that makes possible to add "middleware" for fetch function like this:

async function middleware (request, next) {
  doSomethingBefore();

  const response = await next(request);

  doSomethingAfter();

  return response;
}

Theoretically, I can write an middleware that adds some kind of validation of the response based on headers for example and not on body like this:

async function middleware (request, next) {
  const response = await next(request);

  if (isInvalidHeaders(response)) {
    throw Error('Validation error...')
  }

  return response;
}

In this case, the body will not be read since the promise will go into the catch state.

In real world applications there can be a lot of requests that would not pass such validations

Please explain whether this approach can cause problems with memory consumption?

[ronag]

It will be a problem. You can dump the body before throwing.

async function middleware (request, next) {
  const response = await next(request);

  if (isInvalidHeaders(response)) {
    dump(response)
    throw Error('Validation error...')
  }

  return response;
}
async function dump(response) {
  try {
    for await (const chunk of response) {
      return
    }
  } catch { 
    // Do nothing
  }
} 

[krutoo]

Just be careful of any async errors

@ronag Can you give some details about it?

[ronag]

I think cancel returns a promise that can throw?

[krutoo]

@ronag exactly, thank you

[jdalton]

Would this be response.body?.dump()?

[krutoo]

Would this be response.body?.dump()?

@jdalton is it out of Fetch API specification, just for Node.js?