Allow cache.update/add to accept request objects

[jakearchibald]

Usecase:

this.onfetch(function(event) {
  var responsePromise = fetch(event.request);
  event.respondWith(responsePromise);

  responsePromise.then(function(response) {
    caches.get('api').addResponse(event.request.url, response);
  });
});

The above lets me respond from the network but update the cache at the same time. Pretty confident this will be a common pattern. It works, assuming "addResponse" doesn't throw if the url already exists.

This wouldn't work as well:

this.onfetch(function(event) {
  caches.get('api').add(event.request.url);
  event.respondWith(fetch(event.request));
});

Neater, but the two requests could differ in headers so the browser may make two requests.

Ideally:

this.onfetch(function(event) {
  caches.get('api').add(event.request);
  event.respondWith(fetch(event.request));
});

This depends on cache.add taking requests & being smart enough to make a single request.

[alecf]

Just to clarify, are you hoping to be able to do this:

this.onfetch = function(event) {
    event.respondWith(caches.add(event.request));
}

If so, I support this. I think this is a nice API usability thing..

I was going to say "I think this is just a generalization of the add(url) case" but I see that there's kind of a typo in the spec:

  add(...response:URL[]) : Promise;

I suspect that response is supposed to be request

[jakearchibald]

I hadn't thought of caches.add returning a promise for the response. I'm happy with that.

I just want to avoid cases where:

caches.get('api').add(event.request.url);
event.respondWith(fetch(event.request));

…would trigger two requests.

Allowing add to take requests feels right, since it's current argument, a url, is going to be turned into a request anyway, you just don't get control over the methods, headers etc.

(yeah, I think response is supposed to be url or requestUrl in the spec. You can feed responses directly into caches, but urls and requests should work too)

[jakearchibald]

The new cache API is request-based