Fetch + fastboot + jquery detection problem

[vlascik]

If an app has ember-cli-fastboot, ember-fetch and @ember/jquery as dependencies, code in

data/packages/adapter/addon/rest.js

Lines 312 to 323 in 35b8abf

	useFetch: computed(function() {
	let ENV = getOwner(this).resolveRegistration('config:environment');
	// TODO: https://github.com/emberjs/data/issues/6093
	let jQueryIntegrationDisabled = ENV && ENV.EmberENV && ENV.EmberENV._JQUERY_INTEGRATION === false;
	if (jQueryIntegrationDisabled) {
	return true;
	} else if (hasNajax || hasJQuery) {
	return false;
	} else {
	return true;
	}

doesn't seem to end up with fetch, and uses najax instead. Which leads to errors like najax: method jqXHR."getAllResponseHeaders" not implemented

Ideally, fetch would be used instead, perhaps with additional check like

    if (this.fastboot && hasFetch) {
      return true;
    } else if (jQueryIntegrationDisabled) { 

Seems this method was added in #6094

Not sure if there is a reason for current logic though, or how to proceed.

[rwjblue]

Not sure if there is a reason for current logic though

Since ember-data added support via najax long before fetch support and ember-fetch was already commonly in use when we added support for fetch we were forced to preserve the priority fallback order (otherwise it would have been arguably a breaking change).

[rwjblue]

I think the easiest thing to do would be to override useFetch in your application adapter (to be true).

[vlascik]

Yep, that's what I ultimately did, but the current situation is confusing, maybe this should have at least a warning, documentation, or a more permanent solution, like najax deprecation? Don't think that library is used by many anymore.

[snewcomer]

I was looking at this too at some point so thanks for the explanation! Is it worth making an issue to remind us to change for the 4.0 release?

[rwjblue]

I agree with @vlascik, we can (and probably) should issue a deprecation when we detect that we are going to fallback to the najax side of things. Though we'll have to take care to ensure that the deprecation is triggered in both FastBoot and normal browser runtimes (deprecation in FastBoot alone is much less like to actually be seen unless parsing through server logs).