Issues srv.send vs. srv.emit in sap/cap 6

Hi,

I took over a project and came across this error (warning) message in the logs:

[Deprecated] - srv.emit()used to send synchronous 'UPDATE' request.
Please change this to srv.send() instead.

So I found the corresponding call with is like:

const cds = require('@sap/cds')
cds.env.features.fetch_csrf = true
this.on('UPDATE', '*', async (req) => {
  const funcLocApi = await cds.connect.to('API_FUNCTIONALLOCATION')
  const tx = funcLocApi.transaction(req)
  try {
    const query = req.query
    // req.headers contains etag value with 'If-Match' header
    const functionalLocation = await tx.emit({ query, headers: req.headers })
    return functionalLocation
  } catch (error) {
    throw error
  }
})

Content of packages.json - "@sap/cds" : "^5.9.8"

So I thought I simply change this to use srv.send()

// req.headers contains etag value with 'If-Match' header
const headers = req.headers
const data = req.data
const path = req.path
const functionalLocation = await tx.send({ method: 'UPDATE', path, data, headers })

But then I ran into this error message despite set cds.env.features.fetch_csrf = true: CSRF token validation failed

Then I tried to upgrade to "@sap/cds" : "^6.0.4" with additional package "@sap-cloud-sdk/http-client" : "^2.0.6" which seems to be mandatory since CDS version 6.

Running the line of code tx.send({ method: 'UPDATE', path, data, headers }) caused a new error: Conditional headers cannot be specified for &METHOD& operations

So maybe the ETag handling isn't necessary anymore? Otherwise how should I pass the ETag header since it basically is mandatory for an UPDATE / PATCH operation?

For testing purposes I removed the header again with a totally different error message: The specified HTTP method is not allowed for the resource identified by the Data Service Request URI

I played around with method: 'PATCH' which resulted in the exact same error message: The specified HTTP method is not allowed for the resource identified by the Data Service Request URI

So, the question is: do I use srv.send() the wrong way or is there an error since I probably have to pass a custom header since the behavior of srv.send() in 5.9.8 is different than in 6.0.4

Regards,

Andreas