check that item.first function exists before calling

[jennifer-shehane]

• should help with support of jQuery legacy
• fix issue introduced by
  convert regular array of elements to jquery #2870
• close Cypress.io 3.1.3 breaks by legacy jQuery library #2927

[brian-mann]

• needs a test, can likely use an old version of jquery as a fixture
• needs to add comments above the code referencing this issue so we understand why it's necessary

[jennifer-shehane]

So, I haven't been able to directly replicate this with the standard jQuery 2.2.4, but I've been able to replicate with the user's example code - which includes commonjs, so it's a bit of a frakenstein script, which I'd rather not do, but I added a test with this JS script if you can review and see anything problematic with it.

But, I also think it's just common sense to check the existence of something before calling a function on it, so how harmful can the change be (famous last words).

[brian-mann]

deleted

[brian-mann]

There are two primary problems:

1. this utils function must return the first DOM element in the jquery collection. simply not calling item.first() will cause failures in other ways since this function is no longer doing what it's supposed to be doing
2. because this PR does not replicate the actual problem, thats why all the tests are passing. we must have a test that causes the thing we're fixing to actually break

There's also one secondary problem:

1. you shouldn't commit packages/driver/test/cypress/fixtures/jquery-2.2.4-common.js to source control. I see that jquery-3.2.1.js is there, but that shouldn't be committed either. The driver can use a utility called npm-install-version to install multiple versions of the same library into node_modules which can then be used by the .html fixtures and avoiding the need for source control. We do this in packages/driver/test/support/server.coffee for react and it needs to be done for jquery as well - and all fixtures need to be updated to point to the specific version of jquery it needs.

[brian-mann]

We can very simply re-wrap the jquery object in our own controlled jquery object before calling .first()

[jennifer-shehane]

Can we pair on this in our meeting today?

[agon21]

@jennifer-shehane I am getting one of my tests failing due to this error too. item.first is not a function

Any planned date to release this patch on 3.1.6?
Thanks