Revamping link fetching and stuff

link-stuff.md

Obtaining a resource from a link element

All [external resource links] have an algorithm to fetch and process the linked resource.

Individual link types may define their own [fetch and process the linked resource] algorithm, which takes the link element el. But if not otherwise stated, they use the following default fetch and process the linked resource algorithm, given el:

1. If el's href attribute's value...
2. ... stuff ...
3. Fetch request. To process response given the response response:
   1. Let success be true.
   2. If response is a network error, or its status is not an ok status, set success to false.
   3. Fetch any of the critical subresources of the resource. (TODO: this could be defined better, in particular its affect on success and so on.)
   4. [Process the linked resource] given el and success.

Similarly, individual link types may define their process the linked resource algorithm, which takes the link element el a boolean success, and a response response. This typically is done if they want to reuse the fetching steps from the [default fetch and process the linked resource] algorithm, while overriding the processing steps. But if not otherwise stated, they use the following default process the linked resource algorithm, given el and success (ignoring the response):

1. Queue a task on the DOM manipulation task source (?) to perform the following steps:
   1. If success is true, fire an event named load at el.
   2. Otherwise, fire an event named error at el.

rel="stylesheet"

The [process the linked resource] algorithm for stylesheet links is as follows, given el, success, and response:

1. If response's content type is wrong, set success to false.
2. Fire events according to success.
3. If success is true:
   1. Create/add CSS style sheet
   2. Decrement the counter

rel="modulepreload"

The [fetch and process the linked resource] algorithm for modulepreload links is as follows, given el:

1. ... All the steps; never calls process the linked resource, but does its own thing instead ...

rel="preload"

The [fetch and process the linked resource] algorithm for preload links is as follows, given el:

1. ... Lots of the steps, from whatwg/html#4048, to set up the fetch more specially ...
2. [Process the linked resource] given el, success, and response.