Feature proposal: sync-xhr

[clelland]

Posting this here for completeness, there is a corresponding issue at whatwg/xhr#178 for the XHR spec change.

The proposal is to add a new feature, sync-xhr, which is enabled by default (default allowlist is *)

When disabled, calling send() on an XMLHttpRequest object with the async flag set to false will cause a NetworkError exception to be thrown. (This is chosen to avoid adding a new failure path for existing code which makes use of synchronous XHR)

[RByers]

Anything left before calling this done?

[clelland]

Not for this issue, I suppose -- the PR is still out on whatwg/xhr#178, waiting on the changes to be made to HTML before it lands, I believe.

[annevk]

I think I was happy to land whatwg/xhr#177 provided implementation bugs were filed, but I see that in whatwg/xhr#177 you did note it depended on changes to HTML.

[RByers]

This has landed in the spec and shipped in Chrome. Can we just add it to features.md and mark this as closed please? BTW is anything else missing from features.md?

[clelland]

Added.

features.md could use a few changes -- It uses a normative voice when it really shouldn't, and should probably, in most cases, just link directly to the relevant specs, now that those are starting to integrate with FP themselves.

Eventually all of that documentation should be moved somewhere like MDN, but features.md may need to stick around for a while to document the things that aren't really standards yet.