Correct window type

[OliverJAsh]

Previously this would type error:

cy.window().then(window => window.eval('1'));

(window should have type Window & typeof globalThis.)

You may want to fix other instances of Chainable<Window> as well.

• Closes

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• Has a PR for user-facing changes been opened in cypress-documentation?
• Have API changes been updated in the type definitions?
• Have new configuration options been added to the cypress.schema.json?

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[jennifer-shehane]

@OliverJAsh There's an error in the TS Lint, additionally, can you add a test for this? In the appropriate file under cli/types/tests

Error: /root/cypress/cli/types/index.d.ts:1967:82
ERROR: 1967:82  expect  Compile error in [email protected] but not in [email protected].
Fix with a comment '// TypeScript Version: 3.4' just under the header.
Cannot find name 'globalThis'.

    at /root/cypress/node_modules/dtslint/bin/index.js:190:19
    at Generator.next (<anonymous>)
    at fulfilled (/root/cypress/node_modules/dtslint/bin/index.js:5:58)

[karol-majewski]

@OliverJAsh Regarding the issue we talked about — here's a suggestion for how we can really get the right Window yielded by cy.window().

If my suggestion falls outside the scope of this pull request, please let me know — I can open a separate issue or a pull request instead.

Problem

When you run a test with Cypress, there are two Window instances in play.

1. The top Window object in which the Cypress UI lives, and
2. The Window that represents the tested application.

These are different Windows, but they share the same definition. If you define additional properties by using declaration merging, they will appear on both, which in most cases is incorrect and leads to bugs.

Solution

Allow users to define global variables separately.

In cli/types/index.d.ts, define an empty interface called ApplicationWindow.

interface ApplicationWindow {}

Change the definition for cy.window so that the yielded object includes the properties defined by ApplicationWindow.

window(options?: Partial<Loggable & Timeoutable>): Chainable<Window & typeof globalThis & ApplicationWindow>

Usage

The users can now define properties that exist on the yielded window, but not on the window accessed directly inside a Cypress test.

declare global {
  namespace Cypress {
    interface ApplicationWindow {
      __FOO__?: string;
    }
  }
}

[CypressJoseph]

This seems like a spooky/major change? Are we sure this isn't going to impact folks downstream maybe using earlier TS?

[OliverJAsh]

It's needed to support globalThis. It may well affect your users, so you might want to put this PR on hold until more of your users are on 3.4 or above.

[jennifer-shehane]

We've run into this before, so this is not the first time this has been suggested. #4950 (review)

[CypressJoseph]

Since we just accepted a pull to move to 3.0, I'm guessing that's going to be a conflict -- curious if these changes work at that level (3.0)?

[OliverJAsh]

3.4 is the minimum version if we want to use globalThis

Dismissing my previous reviews to allow for others to review actual code changes.

[jennifer-shehane]

@OliverJAsh Can you fix the conflicts? We just made some TS changes that we merged in.

[OliverJAsh]

@jennifer-shehane Done

[sainthkh]

According to the TypeScript breaking changes list, some vendor-specific types are removed in TypeScript 3.1.

I think it's a better idea to apply this PR to Cypress 5.0. It can potentially break users' types.

[jennifer-shehane]

We're looking to release 5.0, with breaking changes. Is it possible to reevaluate this PR?

[sainthkh]

@jennifer-shehane I will.

[sainthkh]

Close in favor of #7806