visit() does not send user agent header as specified

[Songyu-Wang]

Current behavior:

With the new feature in 3.2.0 that enables setting headers for visit(), "user agent" header is not correctly passed to server side

Desired behavior:

user agent header can be passed to server side as specified

Steps to reproduce: (app code and test code)

Using the following code:

cy.visit({
      url: '/',
      headers: {
        'User-Agent': 'bad browser',
        'hello': 'hi'
      }
    })

And observe server side receives something like this:

As shown above, header "hello" is correctly passed, therefore the header setting is recognized by cypress. However, header "User-Agent" is still my real browser which is the error

Versions

cypress 3.2.0

[flotwig]

It's probably because the UA header gets clobbered in two places in request.coffee:

https://github.com/cypress-io/cypress/blob/develop/packages/server/lib/request.coffee#L267
https://github.com/cypress-io/cypress/blob/develop/packages/server/lib/request.coffee#L328

From a first glance, it looks like this is just Cypress trying to pass along the UA of the browser with the request. It'd probably be safe to change these lines to have and !headers["user-agent"] or similar to allow UA to be overridden.

Need to make sure we're normalizing headers to be lowercase before that can happen.

[jennifer-shehane]

You can set the userAgent as a configuration value in your cypress.json file - https://on.cypress.io/configuration#Browser

There's some explanation on why we implemented it this way here: #364

headers lowercase issue: #2879

We should document this more clearly though within the cy.visit() doc though.
I created a new issue in our docs to document this here: cypress-io/cypress-documentation#1498. Our documentation is open source and contributions are welcome. 😄

[jennifer-shehane]

After further discussion - we should probably also at least handle warning the user when passing a User-Agent header that there is another way to implement this (if not change the implementation to work altogether), so we reopened.

[cypress-bot]

The code for this is done in cypress-io/cypress#3920, but has yet to be released.
We'll update this issue and reference the changelog when it's released.

[cypress-bot]

Released in 3.3.0.