[react-native] Avoid using ExecutionEnvironment.canUseDOM

[morrys]

The canUseDOM variable defined with the following condition: !!(typeof window !== 'undefined' && window.document && window.document.createElement);
This condition returns false in react-native context.

The change only affects relay-experimental & tests:

• https://github.com/facebook/relay/blob/master/packages/relay-experimental/QueryResource.js#L155

• https://github.com/facebook/relay/blob/master/packages/relay-experimental/preloadQuery_DEPRECATED.js#L162

• https://github.com/facebook/relay/blob/master/packages/relay-experimental/preloadQuery_DEPRECATED.js#L194

[josephsavona]

What is the issue here?

[morrys]

Hi @josephsavona,
I try to explain myself better:

As specified in the comment below, this condition must be true when “executed in a server environment”.
https://github.com/facebook/relay/blob/master/packages/relay-experimental/QueryResource.js#L153-L157

// NOTE: If we're executing in a server environment, there's no need
// to create temporary retains, since the component will never commit.
if (!ExecutionEnvironment.canUseDOM) {
return {dispose: () => {}};
}

While it is true even when it is executed in a react-native environment because ExecutionEnvironment.canUseDOM is false both on the server side and in react-native.

So even in react-native does not do the temporaryRetain.

[jstejada]

I think this makes sense, will test internally and land

[morrys]

This issue can be closed as it is resolved in this PR #2960.