Proposal: update browser check to look for document

[alexlafroscia]

I've been working on an Ember compatibility library for emotion (ember-emotion) and have been trying to get server-side rendering working by integrating with FastBoot. However, I've been having a bit of trouble because of the way that emotion checks for the browser environment.

In FastBoot, window is defined but document is not. emotion checks for window but then never uses it; it uses document in a number of places to inject the styled into the page.

Is there a reason for this? If not, would you be willing to accept a PR that checks for the presence of document instead, since that's the actual API that emotion depends on?

If you'd like to maintain the check against window for browser-environment detection, would you be willing to explore the ability to inject the reference to document so that it could be overwritten in a case like mine where document isn't available?

[alexlafroscia]

My progress toward supporting server-side rendering can be found in this PR:

alexlafroscia/ember-emotion#16

Although I had to modify this line to check for typeof window !== 'undefined' && typeof document !== 'undefined

emotion/packages/emotion/src/sheet.js

Line 49 in 03023bb

this.isBrowser = typeof window !== 'undefined'

[alexlafroscia]

I've identified two locations in the 9.0.0-2 code that I had to modify to make my SSR solution work with the new version of emotion:

https://github.com/emotion-js/emotion/blob/master/packages/create-emotion/src/index.js#L315

https://github.com/emotion-js/emotion/blob/master/packages/create-emotion/src/utils.js#L74

I think that the first one referenced should import the isBrowser util instead of defining that comparison a second time, and then the util should check window and document.

I'm happy to make this PR myself, just want the go-ahead that you're interested in these changes and that there isn't some additional context around why checking only window is necessary.

[emmatown]

There's no special reason we check for window, I think we don't need to check for window and document, we can just check for document.

[alexlafroscia]

Awesome! In that case, I’ll make a PR with my proposed changes. Thanks @mitchellhamilton

[alexlafroscia]

@mitchellhamilton is there a timeline for when emotion@9 will be released? Or the next beta, at least? I'm excited to release my next version of ember-emotion but need the change I landed here first.

[emmatown]

@alexlafroscia Just published [email protected] on the next tag

[alexlafroscia]

woot! thank you!