Add a way to clear selection with `cy.select()`

[flotwig]

This Stack Overflow question points out that cy.select() can't clear a selection, and apparently, neither can commands like cy.clear(): https://stackoverflow.com/questions/56340978/how-do-i-clear-a-select-input-using-cypress

Things that should work, but don't:

• cy.select([]) should cause no elements to be selected
• cy.clear() with a <select> subject should cause no elements to be selected

Also, maybe cy.select() or cy.select(undefined) should also clear the selection.

[kylerob]

@jennifer-shehane I'm willing to work on this for Hacktoberfest. What should we allow as acceptable inputs to clear using the select command? @flotwig I like how clean cy.select() is, but I think cy.select([]) or cy.select(null/undefined) conveys more meaning to readers. Also I'm not sure how much cy.clear() makes sense with selects because according to the docs ".clear() is just an alias for .type({selectall}{backspace})." Taking that action on a dropdown selects the first option (via selectall), and then backspace is a noop. We could look at expanding the scope of clear to make it more than an alias, but starting with changes to select may be good enough.

[flotwig]

Hey @kylerob, thanks for looking at this. To answer your questions:

cy.select([]) and cy.select(null/undefined) should both clear the input field - since cy.select can accept an array of choices, cy.select([]) semantically means "nothing selected". So I'd expect both to work.

Re: cy.clear - you can probably update cy.clear to check the command subject, and if the command subject is a <select>, chain .select([]) on to it; otherwise, do the default behavior (.type({selectall}{backspace}))

cc @bkucera

[kuceb]

Edit: oh, were talking about multi-value selects. We should accept empty array
you would need to add a test for setting a value to empty array in the spec file here, and edit the select command file: https://github.com/cypress-io/cypress/blob/issue-2957/packages/driver/src/cy/commands/actions/select.coffee

[kylerob]

@flotwig, @bkucera Thanks for the pointers, I'm starting on it now.